diff options
Diffstat (limited to 'kernel/rcutree.c')
| -rw-r--r-- | kernel/rcutree.c | 2681 |
1 files changed, 0 insertions, 2681 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c deleted file mode 100644 index 38ecdda3f55..00000000000 --- a/kernel/rcutree.c +++ /dev/null @@ -1,2681 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright IBM Corporation, 2008 - * - * Authors: Dipankar Sarma <dipankar@in.ibm.com> - * Manfred Spraul <manfred@colorfullife.com> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version - * - * Based on the original work by Paul McKenney <paulmck@us.ibm.com> - * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU - */ -#include <linux/types.h> -#include <linux/kernel.h> -#include <linux/init.h> -#include <linux/spinlock.h> -#include <linux/smp.h> -#include <linux/rcupdate.h> -#include <linux/interrupt.h> -#include <linux/sched.h> -#include <linux/nmi.h> -#include <linux/atomic.h> -#include <linux/bitops.h> -#include <linux/export.h> -#include <linux/completion.h> -#include <linux/moduleparam.h> -#include <linux/percpu.h> -#include <linux/notifier.h> -#include <linux/cpu.h> -#include <linux/mutex.h> -#include <linux/time.h> -#include <linux/kernel_stat.h> -#include <linux/wait.h> -#include <linux/kthread.h> -#include <linux/prefetch.h> -#include <linux/delay.h> -#include <linux/stop_machine.h> - -#include "rcutree.h" -#include <trace/events/rcu.h> - -#include "rcu.h" - -/* Data structures. */ - -static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; - -#define RCU_STATE_INITIALIZER(structname) { \ - .level = { &structname##_state.node[0] }, \ - .levelcnt = { \ - NUM_RCU_LVL_0, /* root of hierarchy. */ \ - NUM_RCU_LVL_1, \ - NUM_RCU_LVL_2, \ - NUM_RCU_LVL_3, \ - NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ - }, \ - .fqs_state = RCU_GP_IDLE, \ - .gpnum = -300, \ - .completed = -300, \ - .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \ - .orphan_nxttail = &structname##_state.orphan_nxtlist, \ - .orphan_donetail = &structname##_state.orphan_donelist, \ - .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \ - .n_force_qs = 0, \ - .n_force_qs_ngp = 0, \ - .name = #structname, \ -} - -struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched); -DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); - -struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh); -DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); - -static struct rcu_state *rcu_state; - -/* - * The rcu_scheduler_active variable transitions from zero to one just - * before the first task is spawned. So when this variable is zero, RCU - * can assume that there is but one task, allowing RCU to (for example) - * optimized synchronize_sched() to a simple barrier(). When this variable - * is one, RCU must actually do all the hard work required to detect real - * grace periods. This variable is also used to suppress boot-time false - * positives from lockdep-RCU error checking. - */ -int rcu_scheduler_active __read_mostly; -EXPORT_SYMBOL_GPL(rcu_scheduler_active); - -/* - * The rcu_scheduler_fully_active variable transitions from zero to one - * during the early_initcall() processing, which is after the scheduler - * is capable of creating new tasks. So RCU processing (for example, - * creating tasks for RCU priority boosting) must be delayed until after - * rcu_scheduler_fully_active transitions from zero to one. We also - * currently delay invocation of any RCU callbacks until after this point. - * - * It might later prove better for people registering RCU callbacks during - * early boot to take responsibility for these callbacks, but one step at - * a time. - */ -static int rcu_scheduler_fully_active __read_mostly; - -#ifdef CONFIG_RCU_BOOST - -/* - * Control variables for per-CPU and per-rcu_node kthreads. These - * handle all flavors of RCU. - */ -static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DEFINE_PER_CPU(char, rcu_cpu_has_work); - -#endif /* #ifdef CONFIG_RCU_BOOST */ - -static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); -static void invoke_rcu_core(void); -static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); - -/* - * Track the rcutorture test sequence number and the update version - * number within a given test. The rcutorture_testseq is incremented - * on every rcutorture module load and unload, so has an odd value - * when a test is running. The rcutorture_vernum is set to zero - * when rcutorture starts and is incremented on each rcutorture update. - * These variables enable correlating rcutorture output with the - * RCU tracing information. - */ -unsigned long rcutorture_testseq; -unsigned long rcutorture_vernum; - -/* State information for rcu_barrier() and friends. */ - -static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; -static atomic_t rcu_barrier_cpu_count; -static DEFINE_MUTEX(rcu_barrier_mutex); -static struct completion rcu_barrier_completion; - -/* - * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s - * permit this function to be invoked without holding the root rcu_node - * structure's ->lock, but of course results can be subject to change. - */ -static int rcu_gp_in_progress(struct rcu_state *rsp) -{ - return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); -} - -/* - * Note a quiescent state. Because we do not need to know - * how many quiescent states passed, just if there was at least - * one since the start of the grace period, this just sets a flag. - * The caller must have disabled preemption. - */ -void rcu_sched_qs(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); - - rdp->passed_quiesce_gpnum = rdp->gpnum; - barrier(); - if (rdp->passed_quiesce == 0) - trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs"); - rdp->passed_quiesce = 1; -} - -void rcu_bh_qs(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); - - rdp->passed_quiesce_gpnum = rdp->gpnum; - barrier(); - if (rdp->passed_quiesce == 0) - trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs"); - rdp->passed_quiesce = 1; -} - -/* - * Note a context switch. This is a quiescent state for RCU-sched, - * and requires special handling for preemptible RCU. - * The caller must have disabled preemption. - */ -void rcu_note_context_switch(int cpu) -{ - trace_rcu_utilization("Start context switch"); - rcu_sched_qs(cpu); - trace_rcu_utilization("End context switch"); -} -EXPORT_SYMBOL_GPL(rcu_note_context_switch); - -DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { - .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, - .dynticks = ATOMIC_INIT(1), -}; - -static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ -static int qhimark = 10000; /* If this many pending, ignore blimit. */ -static int qlowmark = 100; /* Once only this many pending, use blimit. */ - -module_param(blimit, int, 0); -module_param(qhimark, int, 0); -module_param(qlowmark, int, 0); - -int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ -int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; - -module_param(rcu_cpu_stall_suppress, int, 0644); -module_param(rcu_cpu_stall_timeout, int, 0644); - -static void force_quiescent_state(struct rcu_state *rsp, int relaxed); -static int rcu_pending(int cpu); - -/* - * Return the number of RCU-sched batches processed thus far for debug & stats. - */ -long rcu_batches_completed_sched(void) -{ - return rcu_sched_state.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); - -/* - * Return the number of RCU BH batches processed thus far for debug & stats. - */ -long rcu_batches_completed_bh(void) -{ - return rcu_bh_state.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); - -/* - * Force a quiescent state for RCU BH. - */ -void rcu_bh_force_quiescent_state(void) -{ - force_quiescent_state(&rcu_bh_state, 0); -} -EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); - -/* - * Record the number of times rcutorture tests have been initiated and - * terminated. This information allows the debugfs tracing stats to be - * correlated to the rcutorture messages, even when the rcutorture module - * is being repeatedly loaded and unloaded. In other words, we cannot - * store this state in rcutorture itself. - */ -void rcutorture_record_test_transition(void) -{ - rcutorture_testseq++; - rcutorture_vernum = 0; -} -EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); - -/* - * Record the number of writer passes through the current rcutorture test. - * This is also used to correlate debugfs tracing stats with the rcutorture - * messages. - */ -void rcutorture_record_progress(unsigned long vernum) -{ - rcutorture_vernum++; -} -EXPORT_SYMBOL_GPL(rcutorture_record_progress); - -/* - * Force a quiescent state for RCU-sched. - */ -void rcu_sched_force_quiescent_state(void) -{ - force_quiescent_state(&rcu_sched_state, 0); -} -EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); - -/* - * Does the CPU have callbacks ready to be invoked? - */ -static int -cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) -{ - return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; -} - -/* - * Does the current CPU require a yet-as-unscheduled grace period? - */ -static int -cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) -{ - return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); -} - -/* - * Return the root node of the specified rcu_state structure. - */ -static struct rcu_node *rcu_get_root(struct rcu_state *rsp) -{ - return &rsp->node[0]; -} - -/* - * If the specified CPU is offline, tell the caller that it is in - * a quiescent state. Otherwise, whack it with a reschedule IPI. - * Grace periods can end up waiting on an offline CPU when that - * CPU is in the process of coming online -- it will be added to the - * rcu_node bitmasks before it actually makes it online. The same thing - * can happen while a CPU is in the process of coming online. Because this - * race is quite rare, we check for it after detecting that the grace - * period has been delayed rather than checking each and every CPU - * each and every time we start a new grace period. - */ -static int rcu_implicit_offline_qs(struct rcu_data *rdp) -{ - /* - * If the CPU is offline for more than a jiffy, it is in a quiescent - * state. We can trust its state not to change because interrupts - * are disabled. The reason for the jiffy's worth of slack is to - * handle CPUs initializing on the way up and finding their way - * to the idle loop on the way down. - */ - if (cpu_is_offline(rdp->cpu) && - ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) { - trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl"); - rdp->offline_fqs++; - return 1; - } - return 0; -} - -/* - * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle - * - * If the new value of the ->dynticks_nesting counter now is zero, - * we really have entered idle, and must do the appropriate accounting. - * The caller must have disabled interrupts. - */ -static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) -{ - trace_rcu_dyntick("Start", oldval, 0); - if (!is_idle_task(current)) { - struct task_struct *idle = idle_task(smp_processor_id()); - - trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); - ftrace_dump(DUMP_ALL); - WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", - current->pid, current->comm, - idle->pid, idle->comm); /* must be idle task! */ - } - rcu_prepare_for_idle(smp_processor_id()); - /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ - smp_mb__before_atomic_inc(); /* See above. */ - atomic_inc(&rdtp->dynticks); - smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ - WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); - - /* - * The idle task is not permitted to enter the idle loop while - * in an RCU read-side critical section. - */ - rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), - "Illegal idle entry in RCU read-side critical section."); - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), - "Illegal idle entry in RCU-bh read-side critical section."); - rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), - "Illegal idle entry in RCU-sched read-side critical section."); -} - -/** - * rcu_idle_enter - inform RCU that current CPU is entering idle - * - * Enter idle mode, in other words, -leave- the mode in which RCU - * read-side critical sections can occur. (Though RCU read-side - * critical sections can occur in irq handlers in idle, a possibility - * handled by irq_enter() and irq_exit().) - * - * We crowbar the ->dynticks_nesting field to zero to allow for - * the possibility of usermode upcalls having messed up our count - * of interrupt nesting level during the prior busy period. - */ -void rcu_idle_enter(void) -{ - unsigned long flags; - long long oldval; - struct rcu_dynticks *rdtp; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); - if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) - rdtp->dynticks_nesting = 0; - else - rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; - rcu_idle_enter_common(rdtp, oldval); - local_irq_restore(flags); -} -EXPORT_SYMBOL_GPL(rcu_idle_enter); - -/** - * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle - * - * Exit from an interrupt handler, which might possibly result in entering - * idle mode, in other words, leaving the mode in which read-side critical - * sections can occur. - * - * This code assumes that the idle loop never does anything that might - * result in unbalanced calls to irq_enter() and irq_exit(). If your - * architecture violates this assumption, RCU will give you what you - * deserve, good and hard. But very infrequently and irreproducibly. - * - * Use things like work queues to work around this limitation. - * - * You have been warned. - */ -void rcu_irq_exit(void) -{ - unsigned long flags; - long long oldval; - struct rcu_dynticks *rdtp; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - rdtp->dynticks_nesting--; - WARN_ON_ONCE(rdtp->dynticks_nesting < 0); - if (rdtp->dynticks_nesting) - trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); - else - rcu_idle_enter_common(rdtp, oldval); - local_irq_restore(flags); -} - -/* - * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle - * - * If the new value of the ->dynticks_nesting counter was previously zero, - * we really have exited idle, and must do the appropriate accounting. - * The caller must have disabled interrupts. - */ -static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) -{ - smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ - atomic_inc(&rdtp->dynticks); - /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ - smp_mb__after_atomic_inc(); /* See above. */ - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); - rcu_cleanup_after_idle(smp_processor_id()); - trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); - if (!is_idle_task(current)) { - struct task_struct *idle = idle_task(smp_processor_id()); - - trace_rcu_dyntick("Error on exit: not idle task", - oldval, rdtp->dynticks_nesting); - ftrace_dump(DUMP_ALL); - WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", - current->pid, current->comm, - idle->pid, idle->comm); /* must be idle task! */ - } -} - -/** - * rcu_idle_exit - inform RCU that current CPU is leaving idle - * - * Exit idle mode, in other words, -enter- the mode in which RCU - * read-side critical sections can occur. - * - * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to - * allow for the possibility of usermode upcalls messing up our count - * of interrupt nesting level during the busy period that is just - * now starting. - */ -void rcu_idle_exit(void) -{ - unsigned long flags; - struct rcu_dynticks *rdtp; - long long oldval; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - WARN_ON_ONCE(oldval < 0); - if (oldval & DYNTICK_TASK_NEST_MASK) - rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; - else - rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; - rcu_idle_exit_common(rdtp, oldval); - local_irq_restore(flags); -} -EXPORT_SYMBOL_GPL(rcu_idle_exit); - -/** - * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle - * - * Enter an interrupt handler, which might possibly result in exiting - * idle mode, in other words, entering the mode in which read-side critical - * sections can occur. - * - * Note that the Linux kernel is fully capable of entering an interrupt - * handler that it never exits, for example when doing upcalls to - * user mode! This code assumes that the idle loop never does upcalls to - * user mode. If your architecture does do upcalls from the idle loop (or - * does anything else that results in unbalanced calls to the irq_enter() - * and irq_exit() functions), RCU will give you what you deserve, good - * and hard. But very infrequently and irreproducibly. - * - * Use things like work queues to work around this limitation. - * - * You have been warned. - */ -void rcu_irq_enter(void) -{ - unsigned long flags; - struct rcu_dynticks *rdtp; - long long oldval; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - rdtp->dynticks_nesting++; - WARN_ON_ONCE(rdtp->dynticks_nesting == 0); - if (oldval) - trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); - else - rcu_idle_exit_common(rdtp, oldval); - local_irq_restore(flags); -} - -/** - * rcu_nmi_enter - inform RCU of entry to NMI context - * - * If the CPU was idle with dynamic ticks active, and there is no - * irq handler running, this updates rdtp->dynticks_nmi to let the - * RCU grace-period handling know that the CPU is active. - */ -void rcu_nmi_enter(void) -{ - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (rdtp->dynticks_nmi_nesting == 0 && - (atomic_read(&rdtp->dynticks) & 0x1)) - return; - rdtp->dynticks_nmi_nesting++; - smp_mb__before_atomic_inc(); /* Force delay from prior write. */ - atomic_inc(&rdtp->dynticks); - /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ - smp_mb__after_atomic_inc(); /* See above. */ - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); -} - -/** - * rcu_nmi_exit - inform RCU of exit from NMI context - * - * If the CPU was idle with dynamic ticks active, and there is no - * irq handler running, this updates rdtp->dynticks_nmi to let the - * RCU grace-period handling know that the CPU is no longer active. - */ -void rcu_nmi_exit(void) -{ - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (rdtp->dynticks_nmi_nesting == 0 || - --rdtp->dynticks_nmi_nesting != 0) - return; - /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ - smp_mb__before_atomic_inc(); /* See above. */ - atomic_inc(&rdtp->dynticks); - smp_mb__after_atomic_inc(); /* Force delay to next write. */ - WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); -} - -#ifdef CONFIG_PROVE_RCU - -/** - * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle - * - * If the current CPU is in its idle loop and is neither in an interrupt - * or NMI handler, return true. - */ -int rcu_is_cpu_idle(void) -{ - int ret; - - preempt_disable(); - ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; - preempt_enable(); - return ret; -} -EXPORT_SYMBOL(rcu_is_cpu_idle); - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Is the current CPU online? Disable preemption to avoid false positives - * that could otherwise happen due to the current CPU number being sampled, - * this task being preempted, its old CPU being taken offline, resuming - * on some other CPU, then determining that its old CPU is now offline. - * It is OK to use RCU on an offline processor during initial boot, hence - * the check for rcu_scheduler_fully_active. Note also that it is OK - * for a CPU coming online to use RCU for one jiffy prior to marking itself - * online in the cpu_online_mask. Similarly, it is OK for a CPU going - * offline to continue to use RCU for one jiffy after marking itself - * offline in the cpu_online_mask. This leniency is necessary given the - * non-atomic nature of the online and offline processing, for example, - * the fact that a CPU enters the scheduler after completing the CPU_DYING - * notifiers. - * - * This is also why RCU internally marks CPUs online during the - * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. - * - * Disable checking if in an NMI handler because we cannot safely report - * errors from NMI handlers anyway. - */ -bool rcu_lockdep_current_cpu_online(void) -{ - struct rcu_data *rdp; - struct rcu_node *rnp; - bool ret; - - if (in_nmi()) - return 1; - preempt_disable(); - rdp = &__get_cpu_var(rcu_sched_data); - rnp = rdp->mynode; - ret = (rdp->grpmask & rnp->qsmaskinit) || - !rcu_scheduler_fully_active; - preempt_enable(); - return ret; -} -EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); - -#endif /* #ifdef CONFIG_HOTPLUG_CPU */ - -#endif /* #ifdef CONFIG_PROVE_RCU */ - -/** - * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle - * - * If the current CPU is idle or running at a first-level (not nested) - * interrupt from idle, return true. The caller must have at least - * disabled preemption. - */ -int rcu_is_cpu_rrupt_from_idle(void) -{ - return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; -} - -/* - * Snapshot the specified CPU's dynticks counter so that we can later - * credit them with an implicit quiescent state. Return 1 if this CPU - * is in dynticks idle mode, which is an extended quiescent state. - */ -static int dyntick_save_progress_counter(struct rcu_data *rdp) -{ - rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); - return (rdp->dynticks_snap & 0x1) == 0; -} - -/* - * Return true if the specified CPU has passed through a quiescent - * state by virtue of being in or having passed through an dynticks - * idle state since the last call to dyntick_save_progress_counter() - * for this same CPU. - */ -static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) -{ - unsigned int curr; - unsigned int snap; - - curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); - snap = (unsigned int)rdp->dynticks_snap; - - /* - * If the CPU passed through or entered a dynticks idle phase with - * no active irq/NMI handlers, then we can safely pretend that the CPU - * already acknowledged the request to pass through a quiescent - * state. Either way, that CPU cannot possibly be in an RCU - * read-side critical section that started before the beginning - * of the current RCU grace period. - */ - if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { - trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti"); - rdp->dynticks_fqs++; - return 1; - } - - /* Go check for the CPU being offline. */ - return rcu_implicit_offline_qs(rdp); -} - -static int jiffies_till_stall_check(void) -{ - int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); - - /* - * Limit check must be consistent with the Kconfig limits - * for CONFIG_RCU_CPU_STALL_TIMEOUT. - */ - if (till_stall_check < 3) { - ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; - till_stall_check = 3; - } else if (till_stall_check > 300) { - ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; - till_stall_check = 300; - } - return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; -} - -static void record_gp_stall_check_time(struct rcu_state *rsp) -{ - rsp->gp_start = jiffies; - rsp->jiffies_stall = jiffies + jiffies_till_stall_check(); -} - -static void print_other_cpu_stall(struct rcu_state *rsp) -{ - int cpu; - long delta; - unsigned long flags; - int ndetected; - struct rcu_node *rnp = rcu_get_root(rsp); - - /* Only let one CPU complain about others per time interval. */ - - raw_spin_lock_irqsave(&rnp->lock, flags); - delta = jiffies - rsp->jiffies_stall; - if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - /* - * OK, time to rat on our buddy... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:", - rsp->name); - print_cpu_stall_info_begin(); - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave(&rnp->lock, flags); - ndetected += rcu_print_task_stall(rnp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - if (rnp->qsmask == 0) - continue; - for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) - if (rnp->qsmask & (1UL << cpu)) { - print_cpu_stall_info(rsp, rnp->grplo + cpu); - ndetected++; - } - } - - /* - * Now rat on any tasks that got kicked up to the root rcu_node - * due to CPU offlining. - */ - rnp = rcu_get_root(rsp); - raw_spin_lock_irqsave(&rnp->lock, flags); - ndetected = rcu_print_task_stall(rnp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - print_cpu_stall_info_end(); - printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n", - smp_processor_id(), (long)(jiffies - rsp->gp_start)); - if (ndetected == 0) - printk(KERN_ERR "INFO: Stall ended before state dump start\n"); - else if (!trigger_all_cpu_backtrace()) - dump_stack(); - - /* If so configured, complain about tasks blocking the grace period. */ - - rcu_print_detail_task_stall(rsp); - - force_quiescent_state(rsp, 0); /* Kick them all. */ -} - -static void print_cpu_stall(struct rcu_state *rsp) -{ - unsigned long flags; - struct rcu_node *rnp = rcu_get_root(rsp); - - /* - * OK, time to rat on ourselves... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name); - print_cpu_stall_info_begin(); - print_cpu_stall_info(rsp, smp_processor_id()); - print_cpu_stall_info_end(); - printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start); - if (!trigger_all_cpu_backtrace()) - dump_stack(); - - raw_spin_lock_irqsave(&rnp->lock, flags); - if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) - rsp->jiffies_stall = jiffies + - 3 * jiffies_till_stall_check() + 3; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - set_need_resched(); /* kick ourselves to get things going. */ -} - -static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long j; - unsigned long js; - struct rcu_node *rnp; - - if (rcu_cpu_stall_suppress) - return; - j = ACCESS_ONCE(jiffies); - js = ACCESS_ONCE(rsp->jiffies_stall); - rnp = rdp->mynode; - if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { - - /* We haven't checked in, so go dump stack. */ - print_cpu_stall(rsp); - - } else if (rcu_gp_in_progress(rsp) && - ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { - - /* They had a few time units to dump stack, so complain. */ - print_other_cpu_stall(rsp); - } -} - -static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) -{ - rcu_cpu_stall_suppress = 1; - return NOTIFY_DONE; -} - -/** - * rcu_cpu_stall_reset - prevent further stall warnings in current grace period - * - * Set the stall-warning timeout way off into the future, thus preventing - * any RCU CPU stall-warning messages from appearing in the current set of - * RCU grace periods. - * - * The caller must disable hard irqs. - */ -void rcu_cpu_stall_reset(void) -{ - rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; - rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; - rcu_preempt_stall_reset(); -} - -static struct notifier_block rcu_panic_block = { - .notifier_call = rcu_panic, -}; - -static void __init check_cpu_stall_init(void) -{ - atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); -} - -/* - * Update CPU-local rcu_data state to record the newly noticed grace period. - * This is used both when we started the grace period and when we notice - * that someone else started the grace period. The caller must hold the - * ->lock of the leaf rcu_node structure corresponding to the current CPU, - * and must have irqs disabled. - */ -static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) -{ - if (rdp->gpnum != rnp->gpnum) { - /* - * If the current grace period is waiting for this CPU, - * set up to detect a quiescent state, otherwise don't - * go looking for one. - */ - rdp->gpnum = rnp->gpnum; - trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart"); - if (rnp->qsmask & rdp->grpmask) { - rdp->qs_pending = 1; - rdp->passed_quiesce = 0; - } else - rdp->qs_pending = 0; - zero_cpu_stall_ticks(rdp); - } -} - -static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - struct rcu_node *rnp; - - local_irq_save(flags); - rnp = rdp->mynode; - if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ - !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ - local_irq_restore(flags); - return; - } - __note_new_gpnum(rsp, rnp, rdp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Did someone else start a new RCU grace period start since we last - * checked? Update local state appropriately if so. Must be called - * on the CPU corresponding to rdp. - */ -static int -check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - int ret = 0; - - local_irq_save(flags); - if (rdp->gpnum != rsp->gpnum) { - note_new_gpnum(rsp, rdp); - ret = 1; - } - local_irq_restore(flags); - return ret; -} - -/* - * Advance this CPU's callbacks, but only if the current grace period - * has ended. This may be called only from the CPU to whom the rdp - * belongs. In addition, the corresponding leaf rcu_node structure's - * ->lock must be held by the caller, with irqs disabled. - */ -static void -__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) -{ - /* Did another grace period end? */ - if (rdp->completed != rnp->completed) { - - /* Advance callbacks. No harm if list empty. */ - rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; - rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; - - /* Remember that we saw this grace-period completion. */ - rdp->completed = rnp->completed; - trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend"); - - /* - * If we were in an extended quiescent state, we may have - * missed some grace periods that others CPUs handled on - * our behalf. Catch up with this state to avoid noting - * spurious new grace periods. If another grace period - * has started, then rnp->gpnum will have advanced, so - * we will detect this later on. - */ - if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) - rdp->gpnum = rdp->completed; - - /* - * If RCU does not need a quiescent state from this CPU, - * then make sure that this CPU doesn't go looking for one. - */ - if ((rnp->qsmask & rdp->grpmask) == 0) - rdp->qs_pending = 0; - } -} - -/* - * Advance this CPU's callbacks, but only if the current grace period - * has ended. This may be called only from the CPU to whom the rdp - * belongs. - */ -static void -rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - struct rcu_node *rnp; - - local_irq_save(flags); - rnp = rdp->mynode; - if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ - !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ - local_irq_restore(flags); - return; - } - __rcu_process_gp_end(rsp, rnp, rdp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Do per-CPU grace-period initialization for running CPU. The caller - * must hold the lock of the leaf rcu_node structure corresponding to - * this CPU. - */ -static void -rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) -{ - /* Prior grace period ended, so advance callbacks for current CPU. */ - __rcu_process_gp_end(rsp, rnp, rdp); - - /* - * Because this CPU just now started the new grace period, we know - * that all of its callbacks will be covered by this upcoming grace - * period, even the ones that were registered arbitrarily recently. - * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. - * - * Other CPUs cannot be sure exactly when the grace period started. - * Therefore, their recently registered callbacks must pass through - * an additional RCU_NEXT_READY stage, so that they will be handled - * by the next RCU grace period. - */ - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; - rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; - - /* Set state so that this CPU will detect the next quiescent state. */ - __note_new_gpnum(rsp, rnp, rdp); -} - -/* - * Start a new RCU grace period if warranted, re-initializing the hierarchy - * in preparation for detecting the next grace period. The caller must hold - * the root node's ->lock, which is released before return. Hard irqs must - * be disabled. - * - * Note that it is legal for a dying CPU (which is marked as offline) to - * invoke this function. This can happen when the dying CPU reports its - * quiescent state. - */ -static void -rcu_start_gp(struct rcu_state *rsp, unsigned long flags) - __releases(rcu_get_root(rsp)->lock) -{ - struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - struct rcu_node *rnp = rcu_get_root(rsp); - - if (!rcu_scheduler_fully_active || - !cpu_needs_another_gp(rsp, rdp)) { - /* - * Either the scheduler hasn't yet spawned the first - * non-idle task or this CPU does not need another - * grace period. Either way, don't start a new grace - * period. - */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - - if (rsp->fqs_active) { - /* - * This CPU needs a grace period, but force_quiescent_state() - * is running. Tell it to start one on this CPU's behalf. - */ - rsp->fqs_need_gp = 1; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - - /* Advance to a new grace period and initialize state. */ - rsp->gpnum++; - trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); - WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); - rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */ - rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - record_gp_stall_check_time(rsp); - raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ - - /* Exclude any concurrent CPU-hotplug operations. */ - raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ - - /* - * Set the quiescent-state-needed bits in all the rcu_node - * structures for all currently online CPUs in breadth-first - * order, starting from the root rcu_node structure. This - * operation relies on the layout of the hierarchy within the - * rsp->node[] array. Note that other CPUs will access only - * the leaves of the hierarchy, which still indicate that no - * grace period is in progress, at least until the corresponding - * leaf node has been initialized. In addition, we have excluded - * CPU-hotplug operations. - * - * Note that the grace period cannot complete until we finish - * the initialization process, as there will be at least one - * qsmask bit set in the root node until that time, namely the - * one corresponding to this CPU, due to the fact that we have - * irqs disabled. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rcu_preempt_check_blocked_tasks(rnp); - rnp->qsmask = rnp->qsmaskinit; - rnp->gpnum = rsp->gpnum; - rnp->completed = rsp->completed; - if (rnp == rdp->mynode) - rcu_start_gp_per_cpu(rsp, rnp, rdp); - rcu_preempt_boost_start_gp(rnp); - trace_rcu_grace_period_init(rsp->name, rnp->gpnum, - rnp->level, rnp->grplo, - rnp->grphi, rnp->qsmask); - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - } - - rnp = rcu_get_root(rsp); - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - raw_spin_unlock_irqrestore(&rsp->onofflock, flags); -} - -/* - * Report a full set of quiescent states to the specified rcu_state - * data structure. This involves cleaning up after the prior grace - * period and letting rcu_start_gp() start up the next grace period - * if one is needed. Note that the caller must hold rnp->lock, as - * required by rcu_start_gp(), which will release it. - */ -static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) - __releases(rcu_get_root(rsp)->lock) -{ - unsigned long gp_duration; - struct rcu_node *rnp = rcu_get_root(rsp); - struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - - WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); - - /* - * Ensure that all grace-period and pre-grace-period activity - * is seen before the assignment to rsp->completed. - */ - smp_mb(); /* See above block comment. */ - gp_duration = jiffies - rsp->gp_start; - if (gp_duration > rsp->gp_max) - rsp->gp_max = gp_duration; - - /* - * We know the grace period is complete, but to everyone else - * it appears to still be ongoing. But it is also the case - * that to everyone else it looks like there is nothing that - * they can do to advance the grace period. It is therefore - * safe for us to drop the lock in order to mark the grace - * period as completed in all of the rcu_node structures. - * - * But if this CPU needs another grace period, it will take - * care of this while initializing the next grace period. - * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL - * because the callbacks have not yet been advanced: Those - * callbacks are waiting on the grace period that just now - * completed. - */ - if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - - /* - * Propagate new ->completed value to rcu_node structures - * so that other CPUs don't have to wait until the start - * of the next grace period to process their callbacks. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rnp->completed = rsp->gpnum; - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - } - rnp = rcu_get_root(rsp); - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - } - - rsp->completed = rsp->gpnum; /* Declare the grace period complete. */ - trace_rcu_grace_period(rsp->name, rsp->completed, "end"); - rsp->fqs_state = RCU_GP_IDLE; - rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ -} - -/* - * Similar to rcu_report_qs_rdp(), for which it is a helper function. - * Allows quiescent states for a group of CPUs to be reported at one go - * to the specified rcu_node structure, though all the CPUs in the group - * must be represented by the same rcu_node structure (which need not be - * a leaf rcu_node structure, though it often will be). That structure's - * lock must be held upon entry, and it is released before return. - */ -static void -rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, - struct rcu_node *rnp, unsigned long flags) - __releases(rnp->lock) -{ - struct rcu_node *rnp_c; - - /* Walk up the rcu_node hierarchy. */ - for (;;) { - if (!(rnp->qsmask & mask)) { - - /* Our bit has already been cleared, so done. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - rnp->qsmask &= ~mask; - trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, - mask, rnp->qsmask, rnp->level, - rnp->grplo, rnp->grphi, - !!rnp->gp_tasks); - if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { - - /* Other bits still set at this level, so done. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - mask = rnp->grpmask; - if (rnp->parent == NULL) { - - /* No more levels. Exit loop holding root lock. */ - - break; - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - rnp_c = rnp; - rnp = rnp->parent; - raw_spin_lock_irqsave(&rnp->lock, flags); - WARN_ON_ONCE(rnp_c->qsmask); - } - - /* - * Get here if we are the last CPU to pass through a quiescent - * state for this grace period. Invoke rcu_report_qs_rsp() - * to clean up and start the next grace period if one is needed. - */ - rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ -} - -/* - * Record a quiescent state for the specified CPU to that CPU's rcu_data - * structure. This must be either called from the specified CPU, or - * called when the specified CPU is known to be offline (and when it is - * also known that no other CPU is concurrently trying to help the offline - * CPU). The lastcomp argument is used to make sure we are still in the - * grace period of interest. We don't want to end the current grace period - * based on quiescent states detected in an earlier grace period! - */ -static void -rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp) -{ - unsigned long flags; - unsigned long mask; - struct rcu_node *rnp; - - rnp = rdp->mynode; - raw_spin_lock_irqsave(&rnp->lock, flags); - if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) { - - /* - * The grace period in which this quiescent state was - * recorded has ended, so don't report it upwards. - * We will instead need a new quiescent state that lies - * within the current grace period. - */ - rdp->passed_quiesce = 0; /* need qs for new gp. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - mask = rdp->grpmask; - if ((rnp->qsmask & mask) == 0) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } else { - rdp->qs_pending = 0; - - /* - * This GP can't end until cpu checks in, so all of our - * callbacks can be processed during the next GP. - */ - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; - - rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ - } -} - -/* - * Check to see if there is a new grace period of which this CPU - * is not yet aware, and if so, set up local rcu_data state for it. - * Otherwise, see if this CPU has just passed through its first - * quiescent state for this grace period, and record that fact if so. - */ -static void -rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) -{ - /* If there is now a new grace period, record and return. */ - if (check_for_new_grace_period(rsp, rdp)) - return; - - /* - * Does this CPU still need to do its part for current grace period? - * If no, return and let the other CPUs do their part as well. - */ - if (!rdp->qs_pending) - return; - - /* - * Was there a quiescent state since the beginning of the grace - * period? If no, then exit and wait for the next call. - */ - if (!rdp->passed_quiesce) - return; - - /* - * Tell RCU we are done (but rcu_report_qs_rdp() will be the - * judge of that). - */ - rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum); -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Send the specified CPU's RCU callbacks to the orphanage. The - * specified CPU must be offline, and the caller must hold the - * ->onofflock. - */ -static void -rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, - struct rcu_node *rnp, struct rcu_data *rdp) -{ - int i; - - /* - * Orphan the callbacks. First adjust the counts. This is safe - * because ->onofflock excludes _rcu_barrier()'s adoption of - * the callbacks, thus no memory barrier is required. - */ - if (rdp->nxtlist != NULL) { - rsp->qlen_lazy += rdp->qlen_lazy; - rsp->qlen += rdp->qlen; - rdp->n_cbs_orphaned += rdp->qlen; - rdp->qlen_lazy = 0; - rdp->qlen = 0; - } - - /* - * Next, move those callbacks still needing a grace period to - * the orphanage, where some other CPU will pick them up. - * Some of the callbacks might have gone partway through a grace - * period, but that is too bad. They get to start over because we - * cannot assume that grace periods are synchronized across CPUs. - * We don't bother updating the ->nxttail[] array yet, instead - * we just reset the whole thing later on. - */ - if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { - *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; - rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = NULL; - } - - /* - * Then move the ready-to-invoke callbacks to the orphanage, - * where some other CPU will pick them up. These will not be - * required to pass though another grace period: They are done. - */ - if (rdp->nxtlist != NULL) { - *rsp->orphan_donetail = rdp->nxtlist; - rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; - } - - /* Finally, initialize the rcu_data structure's list to empty. */ - rdp->nxtlist = NULL; - for (i = 0; i < RCU_NEXT_SIZE; i++) - rdp->nxttail[i] = &rdp->nxtlist; -} - -/* - * Adopt the RCU callbacks from the specified rcu_state structure's - * orphanage. The caller must hold the ->onofflock. - */ -static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) -{ - int i; - struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); - - /* - * If there is an rcu_barrier() operation in progress, then - * only the task doing that operation is permitted to adopt - * callbacks. To do otherwise breaks rcu_barrier() and friends - * by causing them to fail to wait for the callbacks in the - * orphanage. - */ - if (rsp->rcu_barrier_in_progress && - rsp->rcu_barrier_in_progress != current) - return; - - /* Do the accounting first. */ - rdp->qlen_lazy += rsp->qlen_lazy; - rdp->qlen += rsp->qlen; - rdp->n_cbs_adopted += rsp->qlen; - if (rsp->qlen_lazy != rsp->qlen) - rcu_idle_count_callbacks_posted(); - rsp->qlen_lazy = 0; - rsp->qlen = 0; - - /* - * We do not need a memory barrier here because the only way we - * can get here if there is an rcu_barrier() in flight is if - * we are the task doing the rcu_barrier(). - */ - - /* First adopt the ready-to-invoke callbacks. */ - if (rsp->orphan_donelist != NULL) { - *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; - for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) - if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) - rdp->nxttail[i] = rsp->orphan_donetail; - rsp->orphan_donelist = NULL; - rsp->orphan_donetail = &rsp->orphan_donelist; - } - - /* And then adopt the callbacks that still need a grace period. */ - if (rsp->orphan_nxtlist != NULL) { - *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; - rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; - rsp->orphan_nxtlist = NULL; - rsp->orphan_nxttail = &rsp->orphan_nxtlist; - } -} - -/* - * Trace the fact that this CPU is going offline. - */ -static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) -{ - RCU_TRACE(unsigned long mask); - RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); - RCU_TRACE(struct rcu_node *rnp = rdp->mynode); - - RCU_TRACE(mask = rdp->grpmask); - trace_rcu_grace_period(rsp->name, - rnp->gpnum + 1 - !!(rnp->qsmask & mask), - "cpuofl"); -} - -/* - * The CPU has been completely removed, and some other CPU is reporting - * this fact from process context. Do the remainder of the cleanup, - * including orphaning the outgoing CPU's RCU callbacks, and also - * adopting them, if there is no _rcu_barrier() instance running. - * There can only be one CPU hotplug operation at a time, so no other - * CPU can be attempting to update rcu_cpu_kthread_task. - */ -static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) -{ - unsigned long flags; - unsigned long mask; - int need_report = 0; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ - - /* Adjust any no-longer-needed kthreads. */ - rcu_stop_cpu_kthread(cpu); - rcu_node_kthread_setaffinity(rnp, -1); - - /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ - - /* Exclude any attempts to start a new grace period. */ - raw_spin_lock_irqsave(&rsp->onofflock, flags); - - /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ - rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); - rcu_adopt_orphan_cbs(rsp); - - /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ - mask = rdp->grpmask; /* rnp->grplo is constant. */ - do { - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rnp->qsmaskinit &= ~mask; - if (rnp->qsmaskinit != 0) { - if (rnp != rdp->mynode) - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - break; - } - if (rnp == rdp->mynode) - need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); - else - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - mask = rnp->grpmask; - rnp = rnp->parent; - } while (rnp != NULL); - - /* - * We still hold the leaf rcu_node structure lock here, and - * irqs are still disabled. The reason for this subterfuge is - * because invoking rcu_report_unblock_qs_rnp() with ->onofflock - * held leads to deadlock. - */ - raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ - rnp = rdp->mynode; - if (need_report & RCU_OFL_TASKS_NORM_GP) - rcu_report_unblock_qs_rnp(rnp, flags); - else - raw_spin_unlock_irqrestore(&rnp->lock, flags); - if (need_report & RCU_OFL_TASKS_EXP_GP) - rcu_report_exp_rnp(rsp, rnp, true); -} - -#else /* #ifdef CONFIG_HOTPLUG_CPU */ - -static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) -{ -} - -static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) -{ -} - -static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) -{ -} - -#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Invoke any RCU callbacks that have made it to the end of their grace - * period. Thottle as specified by rdp->blimit. - */ -static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - struct rcu_head *next, *list, **tail; - int bl, count, count_lazy, i; - - /* If no callbacks are ready, just return.*/ - if (!cpu_has_callbacks_ready_to_invoke(rdp)) { - trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); - trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), - need_resched(), is_idle_task(current), - rcu_is_callbacks_kthread()); - return; - } - - /* - * Extract the list of ready callbacks, disabling to prevent - * races with call_rcu() from interrupt handlers. - */ - local_irq_save(flags); - WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); - bl = rdp->blimit; - trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); - list = rdp->nxtlist; - rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = NULL; - tail = rdp->nxttail[RCU_DONE_TAIL]; - for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) - if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) - rdp->nxttail[i] = &rdp->nxtlist; - local_irq_restore(flags); - - /* Invoke callbacks. */ - count = count_lazy = 0; - while (list) { - next = list->next; - prefetch(next); - debug_rcu_head_unqueue(list); - if (__rcu_reclaim(rsp->name, list)) - count_lazy++; - list = next; - /* Stop only if limit reached and CPU has something to do. */ - if (++count >= bl && - (need_resched() || - (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) - break; - } - - local_irq_save(flags); - trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), - is_idle_task(current), - rcu_is_callbacks_kthread()); - - /* Update count, and requeue any remaining callbacks. */ - if (list != NULL) { - *tail = rdp->nxtlist; - rdp->nxtlist = list; - for (i = 0; i < RCU_NEXT_SIZE; i++) - if (&rdp->nxtlist == rdp->nxttail[i]) - rdp->nxttail[i] = tail; - else - break; - } - smp_mb(); /* List handling before counting for rcu_barrier(). */ - rdp->qlen_lazy -= count_lazy; - rdp->qlen -= count; - rdp->n_cbs_invoked += count; - - /* Reinstate batch limit if we have worked down the excess. */ - if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) - rdp->blimit = blimit; - - /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ - if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { - rdp->qlen_last_fqs_check = 0; - rdp->n_force_qs_snap = rsp->n_force_qs; - } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) - rdp->qlen_last_fqs_check = rdp->qlen; - - local_irq_restore(flags); - - /* Re-invoke RCU core processing if there are callbacks remaining. */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) - invoke_rcu_core(); -} - -/* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. If rcu_pending returns - * false, there is no point in invoking rcu_check_callbacks(). - */ -void rcu_check_callbacks(int cpu, int user) -{ - trace_rcu_utilization("Start scheduler-tick"); - increment_cpu_stall_ticks(); - if (user || rcu_is_cpu_rrupt_from_idle()) { - - /* - * Get here if this CPU took its interrupt from user - * mode or from the idle loop, and if this is not a - * nested interrupt. In this case, the CPU is in - * a quiescent state, so note it. - * - * No memory barrier is required here because both - * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local - * variables that other CPUs neither access nor modify, - * at least not while the corresponding CPU is online. - */ - - rcu_sched_qs(cpu); - rcu_bh_qs(cpu); - - } else if (!in_softirq()) { - - /* - * Get here if this CPU did not take its interrupt from - * softirq, in other words, if it is not interrupting - * a rcu_bh read-side critical section. This is an _bh - * critical section, so note it. - */ - - rcu_bh_qs(cpu); - } - rcu_preempt_check_callbacks(cpu); - if (rcu_pending(cpu)) - invoke_rcu_core(); - trace_rcu_utilization("End scheduler-tick"); -} - -/* - * Scan the leaf rcu_node structures, processing dyntick state for any that - * have not yet encountered a quiescent state, using the function specified. - * Also initiate boosting for any threads blocked on the root rcu_node. - * - * The caller must have suppressed start of new grace periods. - */ -static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) -{ - unsigned long bit; - int cpu; - unsigned long flags; - unsigned long mask; - struct rcu_node *rnp; - - rcu_for_each_leaf_node(rsp, rnp) { - mask = 0; - raw_spin_lock_irqsave(&rnp->lock, flags); - if (!rcu_gp_in_progress(rsp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - if (rnp->qsmask == 0) { - rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ - continue; - } - cpu = rnp->grplo; - bit = 1; - for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { - if ((rnp->qsmask & bit) != 0 && - f(per_cpu_ptr(rsp->rda, cpu))) - mask |= bit; - } - if (mask != 0) { - - /* rcu_report_qs_rnp() releases rnp->lock. */ - rcu_report_qs_rnp(mask, rsp, rnp, flags); - continue; - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } - rnp = rcu_get_root(rsp); - if (rnp->qsmask == 0) { - raw_spin_lock_irqsave(&rnp->lock, flags); - rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ - } -} - -/* - * Force quiescent states on reluctant CPUs, and also detect which - * CPUs are in dyntick-idle mode. - */ -static void force_quiescent_state(struct rcu_state *rsp, int relaxed) -{ - unsigned long flags; - struct rcu_node *rnp = rcu_get_root(rsp); - - trace_rcu_utilization("Start fqs"); - if (!rcu_gp_in_progress(rsp)) { - trace_rcu_utilization("End fqs"); - return; /* No grace period in progress, nothing to force. */ - } - if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { - rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ - trace_rcu_utilization("End fqs"); - return; /* Someone else is already on the job. */ - } - if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) - goto unlock_fqs_ret; /* no emergency and done recently. */ - rsp->n_force_qs++; - raw_spin_lock(&rnp->lock); /* irqs already disabled */ - rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - if(!rcu_gp_in_progress(rsp)) { - rsp->n_force_qs_ngp++; - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ - goto unlock_fqs_ret; /* no GP in progress, time updated. */ - } - rsp->fqs_active = 1; - switch (rsp->fqs_state) { - case RCU_GP_IDLE: - case RCU_GP_INIT: - - break; /* grace period idle or initializing, ignore. */ - - case RCU_SAVE_DYNTICK: - if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) - break; /* So gcc recognizes the dead code. */ - - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ - - /* Record dyntick-idle state. */ - force_qs_rnp(rsp, dyntick_save_progress_counter); - raw_spin_lock(&rnp->lock); /* irqs already disabled */ - if (rcu_gp_in_progress(rsp)) - rsp->fqs_state = RCU_FORCE_QS; - break; - - case RCU_FORCE_QS: - - /* Check dyntick-idle state, send IPI to laggarts. */ - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ - force_qs_rnp(rsp, rcu_implicit_dynticks_qs); - - /* Leave state in case more forcing is required. */ - - raw_spin_lock(&rnp->lock); /* irqs already disabled */ - break; - } - rsp->fqs_active = 0; - if (rsp->fqs_need_gp) { - raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ - rsp->fqs_need_gp = 0; - rcu_start_gp(rsp, flags); /* releases rnp->lock */ - trace_rcu_utilization("End fqs"); - return; - } - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ -unlock_fqs_ret: - raw_spin_unlock_irqrestore(&rsp->fqslock, flags); - trace_rcu_utilization("End fqs"); -} - -/* - * This does the RCU core processing work for the specified rcu_state - * and rcu_data structures. This may be called only from the CPU to - * whom the rdp belongs. - */ -static void -__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - - WARN_ON_ONCE(rdp->beenonline == 0); - - /* - * If an RCU GP has gone long enough, go check for dyntick - * idle CPUs and, if needed, send resched IPIs. - */ - if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) - force_quiescent_state(rsp, 1); - - /* - * Advance callbacks in response to end of earlier grace - * period that some other CPU ended. - */ - rcu_process_gp_end(rsp, rdp); - - /* Update RCU state based on any recent quiescent states. */ - rcu_check_quiescent_state(rsp, rdp); - - /* Does this CPU require a not-yet-started grace period? */ - if (cpu_needs_another_gp(rsp, rdp)) { - raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); - rcu_start_gp(rsp, flags); /* releases above lock */ - } - - /* If there are callbacks ready, invoke them. */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) - invoke_rcu_callbacks(rsp, rdp); -} - -/* - * Do RCU core processing for the current CPU. - */ -static void rcu_process_callbacks(struct softirq_action *unused) -{ - trace_rcu_utilization("Start RCU core"); - __rcu_process_callbacks(&rcu_sched_state, - &__get_cpu_var(rcu_sched_data)); - __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); - rcu_preempt_process_callbacks(); - trace_rcu_utilization("End RCU core"); -} - -/* - * Schedule RCU callback invocation. If the specified type of RCU - * does not support RCU priority boosting, just do a direct call, - * otherwise wake up the per-CPU kernel kthread. Note that because we - * are running on the current CPU with interrupts disabled, the - * rcu_cpu_kthread_task cannot disappear out from under us. - */ -static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) -{ - if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) - return; - if (likely(!rsp->boost)) { - rcu_do_batch(rsp, rdp); - return; - } - invoke_rcu_callbacks_kthread(); -} - -static void invoke_rcu_core(void) -{ - raise_softirq(RCU_SOFTIRQ); -} - -static void -__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), - struct rcu_state *rsp, bool lazy) -{ - unsigned long flags; - struct rcu_data *rdp; - - WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ - debug_rcu_head_queue(head); - head->func = func; - head->next = NULL; - - smp_mb(); /* Ensure RCU update seen before callback registry. */ - - /* - * Opportunistically note grace-period endings and beginnings. - * Note that we might see a beginning right after we see an - * end, but never vice versa, since this CPU has to pass through - * a quiescent state betweentimes. - */ - local_irq_save(flags); - rdp = this_cpu_ptr(rsp->rda); - - /* Add the callback to our list. */ - rdp->qlen++; - if (lazy) - rdp->qlen_lazy++; - else - rcu_idle_count_callbacks_posted(); - smp_mb(); /* Count before adding callback for rcu_barrier(). */ - *rdp->nxttail[RCU_NEXT_TAIL] = head; - rdp->nxttail[RCU_NEXT_TAIL] = &head->next; - - if (__is_kfree_rcu_offset((unsigned long)func)) - trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, - rdp->qlen_lazy, rdp->qlen); - else - trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); - - /* If interrupts were disabled, don't dive into RCU core. */ - if (irqs_disabled_flags(flags)) { - local_irq_restore(flags); - return; - } - - /* - * Force the grace period if too many callbacks or too long waiting. - * Enforce hysteresis, and don't invoke force_quiescent_state() - * if some other CPU has recently done so. Also, don't bother - * invoking force_quiescent_state() if the newly enqueued callback - * is the only one waiting for a grace period to complete. - */ - if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { - - /* Are we ignoring a completed grace period? */ - rcu_process_gp_end(rsp, rdp); - check_for_new_grace_period(rsp, rdp); - - /* Start a new grace period if one not already started. */ - if (!rcu_gp_in_progress(rsp)) { - unsigned long nestflag; - struct rcu_node *rnp_root = rcu_get_root(rsp); - - raw_spin_lock_irqsave(&rnp_root->lock, nestflag); - rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ - } else { - /* Give the grace period a kick. */ - rdp->blimit = LONG_MAX; - if (rsp->n_force_qs == rdp->n_force_qs_snap && - *rdp->nxttail[RCU_DONE_TAIL] != head) - force_quiescent_state(rsp, 0); - rdp->n_force_qs_snap = rsp->n_force_qs; - rdp->qlen_last_fqs_check = rdp->qlen; - } - } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) - force_quiescent_state(rsp, 1); - local_irq_restore(flags); -} - -/* - * Queue an RCU-sched callback for invocation after a grace period. - */ -void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_sched_state, 0); -} -EXPORT_SYMBOL_GPL(call_rcu_sched); - -/* - * Queue an RCU callback for invocation after a quicker grace period. - */ -void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_bh_state, 0); -} -EXPORT_SYMBOL_GPL(call_rcu_bh); - -/* - * Because a context switch is a grace period for RCU-sched and RCU-bh, - * any blocking grace-period wait automatically implies a grace period - * if there is only one CPU online at any point time during execution - * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to - * occasionally incorrectly indicate that there are multiple CPUs online - * when there was in fact only one the whole time, as this just adds - * some overhead: RCU still operates correctly. - * - * Of course, sampling num_online_cpus() with preemption enabled can - * give erroneous results if there are concurrent CPU-hotplug operations. - * For example, given a demonic sequence of preemptions in num_online_cpus() - * and CPU-hotplug operations, there could be two or more CPUs online at - * all times, but num_online_cpus() might well return one (or even zero). - * - * However, all such demonic sequences require at least one CPU-offline - * operation. Furthermore, rcu_blocking_is_gp() giving the wrong answer - * is only a problem if there is an RCU read-side critical section executing - * throughout. But RCU-sched and RCU-bh read-side critical sections - * disable either preemption or bh, which prevents a CPU from going offline. - * Therefore, the only way that rcu_blocking_is_gp() can incorrectly return - * that there is only one CPU when in fact there was more than one throughout - * is when there were no RCU readers in the system. If there are no - * RCU readers, the grace period by definition can be of zero length, - * regardless of the number of online CPUs. - */ -static inline int rcu_blocking_is_gp(void) -{ - might_sleep(); /* Check for RCU read-side critical section. */ - return num_online_cpus() <= 1; -} - -/** - * synchronize_sched - wait until an rcu-sched grace period has elapsed. - * - * Control will return to the caller some time after a full rcu-sched - * grace period has elapsed, in other words after all currently executing - * rcu-sched read-side critical sections have completed. These read-side - * critical sections are delimited by rcu_read_lock_sched() and - * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), - * local_irq_disable(), and so on may be used in place of - * rcu_read_lock_sched(). - * - * This means that all preempt_disable code sequences, including NMI and - * hardware-interrupt handlers, in progress on entry will have completed - * before this primitive returns. However, this does not guarantee that - * softirq handlers will have completed, since in some kernels, these - * handlers can run in process context, and can block. - * - * This primitive provides the guarantees made by the (now removed) - * synchronize_kernel() API. In contrast, synchronize_rcu() only - * guarantees that rcu_read_lock() sections will have completed. - * In "classic RCU", these two guarantees happen to be one and - * the same, but can differ in realtime RCU implementations. - */ -void synchronize_sched(void) -{ - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && - !lock_is_held(&rcu_lock_map) && - !lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_sched() in RCU-sched read-side critical section"); - if (rcu_blocking_is_gp()) - return; - wait_rcu_gp(call_rcu_sched); -} -EXPORT_SYMBOL_GPL(synchronize_sched); - -/** - * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. - * - * Control will return to the caller some time after a full rcu_bh grace - * period has elapsed, in other words after all currently executing rcu_bh - * read-side critical sections have completed. RCU read-side critical - * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), - * and may be nested. - */ -void synchronize_rcu_bh(void) -{ - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && - !lock_is_held(&rcu_lock_map) && - !lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); - if (rcu_blocking_is_gp()) - return; - wait_rcu_gp(call_rcu_bh); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_bh); - -static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0); -static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0); - -static int synchronize_sched_expedited_cpu_stop(void *data) -{ - /* - * There must be a full memory barrier on each affected CPU - * between the time that try_stop_cpus() is called and the - * time that it returns. - * - * In the current initial implementation of cpu_stop, the - * above condition is already met when the control reaches - * this point and the following smp_mb() is not strictly - * necessary. Do smp_mb() anyway for documentation and - * robustness against future implementation changes. - */ - smp_mb(); /* See above comment block. */ - return 0; -} - -/** - * synchronize_sched_expedited - Brute-force RCU-sched grace period - * - * Wait for an RCU-sched grace period to elapse, but use a "big hammer" - * approach to force the grace period to end quickly. This consumes - * significant time on all CPUs and is unfriendly to real-time workloads, - * so is thus not recommended for any sort of common-case code. In fact, - * if you are using synchronize_sched_expedited() in a loop, please - * restructure your code to batch your updates, and then use a single - * synchronize_sched() instead. - * - * Note that it is illegal to call this function while holding any lock - * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal - * to call this function from a CPU-hotplug notifier. Failing to observe - * these restriction will result in deadlock. - * - * This implementation can be thought of as an application of ticket - * locking to RCU, with sync_sched_expedited_started and - * sync_sched_expedited_done taking on the roles of the halves - * of the ticket-lock word. Each task atomically increments - * sync_sched_expedited_started upon entry, snapshotting the old value, - * then attempts to stop all the CPUs. If this succeeds, then each - * CPU will have executed a context switch, resulting in an RCU-sched - * grace period. We are then done, so we use atomic_cmpxchg() to - * update sync_sched_expedited_done to match our snapshot -- but - * only if someone else has not already advanced past our snapshot. - * - * On the other hand, if try_stop_cpus() fails, we check the value - * of sync_sched_expedited_done. If it has advanced past our - * initial snapshot, then someone else must have forced a grace period - * some time after we took our snapshot. In this case, our work is - * done for us, and we can simply return. Otherwise, we try again, - * but keep our initial snapshot for purposes of checking for someone - * doing our work for us. - * - * If we fail too many times in a row, we fall back to synchronize_sched(). - */ -void synchronize_sched_expedited(void) -{ - int firstsnap, s, snap, trycount = 0; - - /* Note that atomic_inc_return() implies full memory barrier. */ - firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); - get_online_cpus(); - WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); - - /* - * Each pass through the following loop attempts to force a - * context switch on each CPU. - */ - while (try_stop_cpus(cpu_online_mask, - synchronize_sched_expedited_cpu_stop, - NULL) == -EAGAIN) { - put_online_cpus(); - - /* No joy, try again later. Or just synchronize_sched(). */ - if (trycount++ < 10) - udelay(trycount * num_online_cpus()); - else { - synchronize_sched(); - return; - } - - /* Check to see if someone else did our work for us. */ - s = atomic_read(&sync_sched_expedited_done); - if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) { - smp_mb(); /* ensure test happens before caller kfree */ - return; - } - - /* - * Refetching sync_sched_expedited_started allows later - * callers to piggyback on our grace period. We subtract - * 1 to get the same token that the last incrementer got. - * We retry after they started, so our grace period works - * for them, and they started after our first try, so their - * grace period works for us. - */ - get_online_cpus(); - snap = atomic_read(&sync_sched_expedited_started); - smp_mb(); /* ensure read is before try_stop_cpus(). */ - } - - /* - * Everyone up to our most recent fetch is covered by our grace - * period. Update the counter, but only if our work is still - * relevant -- which it won't be if someone who started later - * than we did beat us to the punch. - */ - do { - s = atomic_read(&sync_sched_expedited_done); - if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) { - smp_mb(); /* ensure test happens before caller kfree */ - break; - } - } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s); - - put_online_cpus(); -} -EXPORT_SYMBOL_GPL(synchronize_sched_expedited); - -/* - * Check to see if there is any immediate RCU-related work to be done - * by the current CPU, for the specified type of RCU, returning 1 if so. - * The checks are in order of increasing expense: checks that can be - * carried out against CPU-local state are performed first. However, - * we must check for CPU stalls first, else we might not get a chance. - */ -static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) -{ - struct rcu_node *rnp = rdp->mynode; - - rdp->n_rcu_pending++; - - /* Check for CPU stalls, if enabled. */ - check_cpu_stall(rsp, rdp); - - /* Is the RCU core waiting for a quiescent state from this CPU? */ - if (rcu_scheduler_fully_active && - rdp->qs_pending && !rdp->passed_quiesce) { - - /* - * If force_quiescent_state() coming soon and this CPU - * needs a quiescent state, and this is either RCU-sched - * or RCU-bh, force a local reschedule. - */ - rdp->n_rp_qs_pending++; - if (!rdp->preemptible && - ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, - jiffies)) - set_need_resched(); - } else if (rdp->qs_pending && rdp->passed_quiesce) { - rdp->n_rp_report_qs++; - return 1; - } - - /* Does this CPU have callbacks ready to invoke? */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) { - rdp->n_rp_cb_ready++; - return 1; - } - - /* Has RCU gone idle with this CPU needing another grace period? */ - if (cpu_needs_another_gp(rsp, rdp)) { - rdp->n_rp_cpu_needs_gp++; - return 1; - } - - /* Has another RCU grace period completed? */ - if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ - rdp->n_rp_gp_completed++; - return 1; - } - - /* Has a new RCU grace period started? */ - if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ - rdp->n_rp_gp_started++; - return 1; - } - - /* Has an RCU GP gone long enough to send resched IPIs &c? */ - if (rcu_gp_in_progress(rsp) && - ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { - rdp->n_rp_need_fqs++; - return 1; - } - - /* nothing to do */ - rdp->n_rp_need_nothing++; - return 0; -} - -/* - * Check to see if there is any immediate RCU-related work to be done - * by the current CPU, returning 1 if so. This function is part of the - * RCU implementation; it is -not- an exported member of the RCU API. - */ -static int rcu_pending(int cpu) -{ - return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || - __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || - rcu_preempt_pending(cpu); -} - -/* - * Check to see if any future RCU-related work will need to be done - * by the current CPU, even if none need be done immediately, returning - * 1 if so. - */ -static int rcu_cpu_has_callbacks(int cpu) -{ - /* RCU callbacks either ready or pending? */ - return per_cpu(rcu_sched_data, cpu).nxtlist || - per_cpu(rcu_bh_data, cpu).nxtlist || - rcu_preempt_cpu_has_callbacks(cpu); -} - -/* - * RCU callback function for _rcu_barrier(). If we are last, wake - * up the task executing _rcu_barrier(). - */ -static void rcu_barrier_callback(struct rcu_head *notused) -{ - if (atomic_dec_and_test(&rcu_barrier_cpu_count)) - complete(&rcu_barrier_completion); -} - -/* - * Called with preemption disabled, and from cross-cpu IRQ context. - */ -static void rcu_barrier_func(void *type) -{ - int cpu = smp_processor_id(); - struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); - void (*call_rcu_func)(struct rcu_head *head, - void (*func)(struct rcu_head *head)); - - atomic_inc(&rcu_barrier_cpu_count); - call_rcu_func = type; - call_rcu_func(head, rcu_barrier_callback); -} - -/* - * Orchestrate the specified type of RCU barrier, waiting for all - * RCU callbacks of the specified type to complete. - */ -static void _rcu_barrier(struct rcu_state *rsp, - void (*call_rcu_func)(struct rcu_head *head, - void (*func)(struct rcu_head *head))) -{ - int cpu; - unsigned long flags; - struct rcu_data *rdp; - struct rcu_head rh; - - init_rcu_head_on_stack(&rh); - - /* Take mutex to serialize concurrent rcu_barrier() requests. */ - mutex_lock(&rcu_barrier_mutex); - - smp_mb(); /* Prevent any prior operations from leaking in. */ - - /* - * Initialize the count to one rather than to zero in order to - * avoid a too-soon return to zero in case of a short grace period - * (or preemption of this task). Also flag this task as doing - * an rcu_barrier(). This will prevent anyone else from adopting - * orphaned callbacks, which could cause otherwise failure if a - * CPU went offline and quickly came back online. To see this, - * consider the following sequence of events: - * - * 1. We cause CPU 0 to post an rcu_barrier_callback() callback. - * 2. CPU 1 goes offline, orphaning its callbacks. - * 3. CPU 0 adopts CPU 1's orphaned callbacks. - * 4. CPU 1 comes back online. - * 5. We cause CPU 1 to post an rcu_barrier_callback() callback. - * 6. Both rcu_barrier_callback() callbacks are invoked, awakening - * us -- but before CPU 1's orphaned callbacks are invoked!!! - */ - init_completion(&rcu_barrier_completion); - atomic_set(&rcu_barrier_cpu_count, 1); - raw_spin_lock_irqsave(&rsp->onofflock, flags); - rsp->rcu_barrier_in_progress = current; - raw_spin_unlock_irqrestore(&rsp->onofflock, flags); - - /* - * Force every CPU with callbacks to register a new callback - * that will tell us when all the preceding callbacks have - * been invoked. If an offline CPU has callbacks, wait for - * it to either come back online or to finish orphaning those - * callbacks. - */ - for_each_possible_cpu(cpu) { - preempt_disable(); - rdp = per_cpu_ptr(rsp->rda, cpu); - if (cpu_is_offline(cpu)) { - preempt_enable(); - while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen)) - schedule_timeout_interruptible(1); - } else if (ACCESS_ONCE(rdp->qlen)) { - smp_call_function_single(cpu, rcu_barrier_func, - (void *)call_rcu_func, 1); - preempt_enable(); - } else { - preempt_enable(); - } - } - - /* - * Now that all online CPUs have rcu_barrier_callback() callbacks - * posted, we can adopt all of the orphaned callbacks and place - * an rcu_barrier_callback() callback after them. When that is done, - * we are guaranteed to have an rcu_barrier_callback() callback - * following every callback that could possibly have been - * registered before _rcu_barrier() was called. - */ - raw_spin_lock_irqsave(&rsp->onofflock, flags); - rcu_adopt_orphan_cbs(rsp); - rsp->rcu_barrier_in_progress = NULL; - raw_spin_unlock_irqrestore(&rsp->onofflock, flags); - atomic_inc(&rcu_barrier_cpu_count); - smp_mb__after_atomic_inc(); /* Ensure atomic_inc() before callback. */ - call_rcu_func(&rh, rcu_barrier_callback); - - /* - * Now that we have an rcu_barrier_callback() callback on each - * CPU, and thus each counted, remove the initial count. - */ - if (atomic_dec_and_test(&rcu_barrier_cpu_count)) - complete(&rcu_barrier_completion); - - /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ - wait_for_completion(&rcu_barrier_completion); - - /* Other rcu_barrier() invocations can now safely proceed. */ - mutex_unlock(&rcu_barrier_mutex); - - destroy_rcu_head_on_stack(&rh); -} - -/** - * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. - */ -void rcu_barrier_bh(void) -{ - _rcu_barrier(&rcu_bh_state, call_rcu_bh); -} -EXPORT_SYMBOL_GPL(rcu_barrier_bh); - -/** - * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. - */ -void rcu_barrier_sched(void) -{ - _rcu_barrier(&rcu_sched_state, call_rcu_sched); -} -EXPORT_SYMBOL_GPL(rcu_barrier_sched); - -/* - * Do boot-time initialization of a CPU's per-CPU RCU data. - */ -static void __init -rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) -{ - unsigned long flags; - int i; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rcu_get_root(rsp); - - /* Set up local state, ensuring consistent view of global state. */ - raw_spin_lock_irqsave(&rnp->lock, flags); - rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); - rdp->nxtlist = NULL; - for (i = 0; i < RCU_NEXT_SIZE; i++) - rdp->nxttail[i] = &rdp->nxtlist; - rdp->qlen_lazy = 0; - rdp->qlen = 0; - rdp->dynticks = &per_cpu(rcu_dynticks, cpu); - WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); - WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); - rdp->cpu = cpu; - rdp->rsp = rsp; - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Initialize a CPU's per-CPU RCU data. Note that only one online or - * offline event can be happening at a given time. Note also that we - * can accept some slop in the rsp->completed access due to the fact - * that this CPU cannot possibly have any RCU callbacks in flight yet. - */ -static void __cpuinit -rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) -{ - unsigned long flags; - unsigned long mask; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rcu_get_root(rsp); - - /* Set up local state, ensuring consistent view of global state. */ - raw_spin_lock_irqsave(&rnp->lock, flags); - rdp->beenonline = 1; /* We have now been online. */ - rdp->preemptible = preemptible; - rdp->qlen_last_fqs_check = 0; - rdp->n_force_qs_snap = rsp->n_force_qs; - rdp->blimit = blimit; - rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; - atomic_set(&rdp->dynticks->dynticks, - (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); - rcu_prepare_for_idle_init(cpu); - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - - /* - * A new grace period might start here. If so, we won't be part - * of it, but that is OK, as we are currently in a quiescent state. - */ - - /* Exclude any attempts to start a new GP on large systems. */ - raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ - - /* Add CPU to rcu_node bitmasks. */ - rnp = rdp->mynode; - mask = rdp->grpmask; - do { - /* Exclude any attempts to start a new GP on small systems. */ - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rnp->qsmaskinit |= mask; - mask = rnp->grpmask; - if (rnp == rdp->mynode) { - /* - * If there is a grace period in progress, we will - * set up to wait for it next time we run the - * RCU core code. - */ - rdp->gpnum = rnp->completed; - rdp->completed = rnp->completed; - rdp->passed_quiesce = 0; - rdp->qs_pending = 0; - rdp->passed_quiesce_gpnum = rnp->gpnum - 1; - trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl"); - } - raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ - rnp = rnp->parent; - } while (rnp != NULL && !(rnp->qsmaskinit & mask)); - - raw_spin_unlock_irqrestore(&rsp->onofflock, flags); -} - -static void __cpuinit rcu_prepare_cpu(int cpu) -{ - rcu_init_percpu_data(cpu, &rcu_sched_state, 0); - rcu_init_percpu_data(cpu, &rcu_bh_state, 0); - rcu_preempt_init_percpu_data(cpu); -} - -/* - * Handle CPU online/offline notification events. - */ -static int __cpuinit rcu_cpu_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - long cpu = (long)hcpu; - struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); - struct rcu_node *rnp = rdp->mynode; - - trace_rcu_utilization("Start CPU hotplug"); - switch (action) { - case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: - rcu_prepare_cpu(cpu); - rcu_prepare_kthreads(cpu); - break; - case CPU_ONLINE: - case CPU_DOWN_FAILED: - rcu_node_kthread_setaffinity(rnp, -1); - rcu_cpu_kthread_setrt(cpu, 1); - break; - case CPU_DOWN_PREPARE: - rcu_node_kthread_setaffinity(rnp, cpu); - rcu_cpu_kthread_setrt(cpu, 0); - break; - case CPU_DYING: - case CPU_DYING_FROZEN: - /* - * The whole machine is "stopped" except this CPU, so we can - * touch any data without introducing corruption. We send the - * dying CPU's callbacks to an arbitrarily chosen online CPU. - */ - rcu_cleanup_dying_cpu(&rcu_bh_state); - rcu_cleanup_dying_cpu(&rcu_sched_state); - rcu_preempt_cleanup_dying_cpu(); - rcu_cleanup_after_idle(cpu); - break; - case CPU_DEAD: - case CPU_DEAD_FROZEN: - case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: - rcu_cleanup_dead_cpu(cpu, &rcu_bh_state); - rcu_cleanup_dead_cpu(cpu, &rcu_sched_state); - rcu_preempt_cleanup_dead_cpu(cpu); - break; - default: - break; - } - trace_rcu_utilization("End CPU hotplug"); - return NOTIFY_OK; -} - -/* - * This function is invoked towards the end of the scheduler's initialization - * process. Before this is called, the idle task might contain - * RCU read-side critical sections (during which time, this idle - * task is booting the system). After this function is called, the - * idle tasks are prohibited from containing RCU read-side critical - * sections. This function also enables RCU lockdep checking. - */ -void rcu_scheduler_starting(void) -{ - WARN_ON(num_online_cpus() != 1); - WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; -} - -/* - * Compute the per-level fanout, either using the exact fanout specified - * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. - */ -#ifdef CONFIG_RCU_FANOUT_EXACT -static void __init rcu_init_levelspread(struct rcu_state *rsp) -{ - int i; - - for (i = NUM_RCU_LVLS - 1; i > 0; i--) - rsp->levelspread[i] = CONFIG_RCU_FANOUT; - rsp->levelspread[0] = CONFIG_RCU_FANOUT_LEAF; -} -#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ -static void __init rcu_init_levelspread(struct rcu_state *rsp) -{ - int ccur; - int cprv; - int i; - - cprv = NR_CPUS; - for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { - ccur = rsp->levelcnt[i]; - rsp->levelspread[i] = (cprv + ccur - 1) / ccur; - cprv = ccur; - } -} -#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ - -/* - * Helper function for rcu_init() that initializes one rcu_state structure. - */ -static void __init rcu_init_one(struct rcu_state *rsp, - struct rcu_data __percpu *rda) -{ - static char *buf[] = { "rcu_node_level_0", - "rcu_node_level_1", - "rcu_node_level_2", - "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ - int cpustride = 1; - int i; - int j; - struct rcu_node *rnp; - - BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ - - /* Initialize the level-tracking arrays. */ - - for (i = 1; i < NUM_RCU_LVLS; i++) - rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; - rcu_init_levelspread(rsp); - - /* Initialize the elements themselves, starting from the leaves. */ - - for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { - cpustride *= rsp->levelspread[i]; - rnp = rsp->level[i]; - for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { - raw_spin_lock_init(&rnp->lock); - lockdep_set_class_and_name(&rnp->lock, - &rcu_node_class[i], buf[i]); - rnp->gpnum = 0; - rnp->qsmask = 0; - rnp->qsmaskinit = 0; - rnp->grplo = j * cpustride; - rnp->grphi = (j + 1) * cpustride - 1; - if (rnp->grphi >= NR_CPUS) - rnp->grphi = NR_CPUS - 1; - if (i == 0) { - rnp->grpnum = 0; - rnp->grpmask = 0; - rnp->parent = NULL; - } else { - rnp->grpnum = j % rsp->levelspread[i - 1]; - rnp->grpmask = 1UL << rnp->grpnum; - rnp->parent = rsp->level[i - 1] + - j / rsp->levelspread[i - 1]; - } - rnp->level = i; - INIT_LIST_HEAD(&rnp->blkd_tasks); - } - } - - rsp->rda = rda; - rnp = rsp->level[NUM_RCU_LVLS - 1]; - for_each_possible_cpu(i) { - while (i > rnp->grphi) - rnp++; - per_cpu_ptr(rsp->rda, i)->mynode = rnp; - rcu_boot_init_percpu_data(i, rsp); - } -} - -void __init rcu_init(void) -{ - int cpu; - - rcu_bootup_announce(); - rcu_init_one(&rcu_sched_state, &rcu_sched_data); - rcu_init_one(&rcu_bh_state, &rcu_bh_data); - __rcu_init_preempt(); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); - - /* - * We don't need protection against CPU-hotplug here because - * this is called early in boot, before either interrupts - * or the scheduler are operational. - */ - cpu_notifier(rcu_cpu_notify, 0); - for_each_online_cpu(cpu) - rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); - check_cpu_stall_init(); -} - -#include "rcutree_plugin.h" |