diff options
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 2497 |
1 files changed, 0 insertions, 2497 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h deleted file mode 100644 index f6e5ec2932b..00000000000 --- a/kernel/rcutree_plugin.h +++ /dev/null @@ -1,2497 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion (tree-based version) - * Internal non-public definitions that provide either classic - * or preemptible semantics. - * - * 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 Red Hat, 2009 - * Copyright IBM Corporation, 2009 - * - * Author: Ingo Molnar <mingo@elte.hu> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> - */ - -#include <linux/delay.h> -#include <linux/gfp.h> -#include <linux/oom.h> -#include <linux/smpboot.h> - -#define RCU_KTHREAD_PRIO 1 - -#ifdef CONFIG_RCU_BOOST -#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO -#else -#define RCU_BOOST_PRIO RCU_KTHREAD_PRIO -#endif - -#ifdef CONFIG_RCU_NOCB_CPU -static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ -static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ -static bool rcu_nocb_poll; /* Offload kthread are to poll. */ -module_param(rcu_nocb_poll, bool, 0444); -static char __initdata nocb_buf[NR_CPUS * 5]; -#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ - -/* - * Check the RCU kernel configuration parameters and print informative - * messages about anything out of the ordinary. If you like #ifdef, you - * will love this function. - */ -static void __init rcu_bootup_announce_oddness(void) -{ -#ifdef CONFIG_RCU_TRACE - printk(KERN_INFO "\tRCU debugfs-based tracing is enabled.\n"); -#endif -#if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) - printk(KERN_INFO "\tCONFIG_RCU_FANOUT set to non-default value of %d\n", - CONFIG_RCU_FANOUT); -#endif -#ifdef CONFIG_RCU_FANOUT_EXACT - printk(KERN_INFO "\tHierarchical RCU autobalancing is disabled.\n"); -#endif -#ifdef CONFIG_RCU_FAST_NO_HZ - printk(KERN_INFO - "\tRCU dyntick-idle grace-period acceleration is enabled.\n"); -#endif -#ifdef CONFIG_PROVE_RCU - printk(KERN_INFO "\tRCU lockdep checking is enabled.\n"); -#endif -#ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE - printk(KERN_INFO "\tRCU torture testing starts during boot.\n"); -#endif -#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE) - printk(KERN_INFO "\tDump stacks of tasks blocking RCU-preempt GP.\n"); -#endif -#if defined(CONFIG_RCU_CPU_STALL_INFO) - printk(KERN_INFO "\tAdditional per-CPU info printed with stalls.\n"); -#endif -#if NUM_RCU_LVL_4 != 0 - printk(KERN_INFO "\tFour-level hierarchy is enabled.\n"); -#endif - if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) - printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); - if (nr_cpu_ids != NR_CPUS) - printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); -#ifdef CONFIG_RCU_NOCB_CPU - if (have_rcu_nocb_mask) { - if (cpumask_test_cpu(0, rcu_nocb_mask)) { - cpumask_clear_cpu(0, rcu_nocb_mask); - pr_info("\tCPU 0: illegal no-CBs CPU (cleared).\n"); - } - cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); - pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf); - if (rcu_nocb_poll) - pr_info("\tExperimental polled no-CBs CPUs.\n"); - } -#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ -} - -#ifdef CONFIG_TREE_PREEMPT_RCU - -struct rcu_state rcu_preempt_state = - RCU_STATE_INITIALIZER(rcu_preempt, call_rcu); -DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); -static struct rcu_state *rcu_state = &rcu_preempt_state; - -static int rcu_preempted_readers_exp(struct rcu_node *rnp); - -/* - * Tell them what RCU they are running. - */ -static void __init rcu_bootup_announce(void) -{ - printk(KERN_INFO "Preemptible hierarchical RCU implementation.\n"); - rcu_bootup_announce_oddness(); -} - -/* - * Return the number of RCU-preempt batches processed thus far - * for debug and statistics. - */ -long rcu_batches_completed_preempt(void) -{ - return rcu_preempt_state.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); - -/* - * Return the number of RCU batches processed thus far for debug & stats. - */ -long rcu_batches_completed(void) -{ - return rcu_batches_completed_preempt(); -} -EXPORT_SYMBOL_GPL(rcu_batches_completed); - -/* - * Force a quiescent state for preemptible RCU. - */ -void rcu_force_quiescent_state(void) -{ - force_quiescent_state(&rcu_preempt_state); -} -EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); - -/* - * Record a preemptible-RCU quiescent state for the specified CPU. Note - * that this just means that the task currently running on the CPU is - * not in a quiescent state. There might be any number of tasks blocked - * while in an RCU read-side critical section. - * - * Unlike the other rcu_*_qs() functions, callers to this function - * must disable irqs in order to protect the assignment to - * ->rcu_read_unlock_special. - */ -static void rcu_preempt_qs(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); - - if (rdp->passed_quiesce == 0) - trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs"); - rdp->passed_quiesce = 1; - current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; -} - -/* - * We have entered the scheduler, and the current task might soon be - * context-switched away from. If this task is in an RCU read-side - * critical section, we will no longer be able to rely on the CPU to - * record that fact, so we enqueue the task on the blkd_tasks list. - * The task will dequeue itself when it exits the outermost enclosing - * RCU read-side critical section. Therefore, the current grace period - * cannot be permitted to complete until the blkd_tasks list entries - * predating the current grace period drain, in other words, until - * rnp->gp_tasks becomes NULL. - * - * Caller must disable preemption. - */ -static void rcu_preempt_note_context_switch(int cpu) -{ - struct task_struct *t = current; - unsigned long flags; - struct rcu_data *rdp; - struct rcu_node *rnp; - - if (t->rcu_read_lock_nesting > 0 && - (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { - - /* Possibly blocking in an RCU read-side critical section. */ - rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu); - rnp = rdp->mynode; - raw_spin_lock_irqsave(&rnp->lock, flags); - t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; - t->rcu_blocked_node = rnp; - - /* - * If this CPU has already checked in, then this task - * will hold up the next grace period rather than the - * current grace period. Queue the task accordingly. - * If the task is queued for the current grace period - * (i.e., this CPU has not yet passed through a quiescent - * state for the current grace period), then as long - * as that task remains queued, the current grace period - * cannot end. Note that there is some uncertainty as - * to exactly when the current grace period started. - * We take a conservative approach, which can result - * in unnecessarily waiting on tasks that started very - * slightly after the current grace period began. C'est - * la vie!!! - * - * But first, note that the current CPU must still be - * on line! - */ - WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); - WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); - if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { - list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); - rnp->gp_tasks = &t->rcu_node_entry; -#ifdef CONFIG_RCU_BOOST - if (rnp->boost_tasks != NULL) - rnp->boost_tasks = rnp->gp_tasks; -#endif /* #ifdef CONFIG_RCU_BOOST */ - } else { - list_add(&t->rcu_node_entry, &rnp->blkd_tasks); - if (rnp->qsmask & rdp->grpmask) - rnp->gp_tasks = &t->rcu_node_entry; - } - trace_rcu_preempt_task(rdp->rsp->name, - t->pid, - (rnp->qsmask & rdp->grpmask) - ? rnp->gpnum - : rnp->gpnum + 1); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } else if (t->rcu_read_lock_nesting < 0 && - t->rcu_read_unlock_special) { - - /* - * Complete exit from RCU read-side critical section on - * behalf of preempted instance of __rcu_read_unlock(). - */ - rcu_read_unlock_special(t); - } - - /* - * Either we were not in an RCU read-side critical section to - * begin with, or we have now recorded that critical section - * globally. Either way, we can now note a quiescent state - * for this CPU. Again, if we were in an RCU read-side critical - * section, and if that critical section was blocking the current - * grace period, then the fact that the task has been enqueued - * means that we continue to block the current grace period. - */ - local_irq_save(flags); - rcu_preempt_qs(cpu); - local_irq_restore(flags); -} - -/* - * Check for preempted RCU readers blocking the current grace period - * for the specified rcu_node structure. If the caller needs a reliable - * answer, it must hold the rcu_node's ->lock. - */ -static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) -{ - return rnp->gp_tasks != NULL; -} - -/* - * Record a quiescent state for all tasks that were previously queued - * on the specified rcu_node structure and that were blocking the current - * RCU grace period. The caller must hold the specified rnp->lock with - * irqs disabled, and this lock is released upon return, but irqs remain - * disabled. - */ -static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) - __releases(rnp->lock) -{ - unsigned long mask; - struct rcu_node *rnp_p; - - if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; /* Still need more quiescent states! */ - } - - rnp_p = rnp->parent; - if (rnp_p == NULL) { - /* - * Either there is only one rcu_node in the tree, - * or tasks were kicked up to root rcu_node due to - * CPUs going offline. - */ - rcu_report_qs_rsp(&rcu_preempt_state, flags); - return; - } - - /* Report up the rest of the hierarchy. */ - mask = rnp->grpmask; - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ - rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); -} - -/* - * Advance a ->blkd_tasks-list pointer to the next entry, instead - * returning NULL if at the end of the list. - */ -static struct list_head *rcu_next_node_entry(struct task_struct *t, - struct rcu_node *rnp) -{ - struct list_head *np; - - np = t->rcu_node_entry.next; - if (np == &rnp->blkd_tasks) - np = NULL; - return np; -} - -/* - * Handle special cases during rcu_read_unlock(), such as needing to - * notify RCU core processing or task having blocked during the RCU - * read-side critical section. - */ -void rcu_read_unlock_special(struct task_struct *t) -{ - int empty; - int empty_exp; - int empty_exp_now; - unsigned long flags; - struct list_head *np; -#ifdef CONFIG_RCU_BOOST - struct rt_mutex *rbmp = NULL; -#endif /* #ifdef CONFIG_RCU_BOOST */ - struct rcu_node *rnp; - int special; - - /* NMI handlers cannot block and cannot safely manipulate state. */ - if (in_nmi()) - return; - - local_irq_save(flags); - - /* - * If RCU core is waiting for this CPU to exit critical section, - * let it know that we have done so. - */ - special = t->rcu_read_unlock_special; - if (special & RCU_READ_UNLOCK_NEED_QS) { - rcu_preempt_qs(smp_processor_id()); - } - - /* Hardware IRQ handlers cannot block. */ - if (in_irq() || in_serving_softirq()) { - local_irq_restore(flags); - return; - } - - /* Clean up if blocked during RCU read-side critical section. */ - if (special & RCU_READ_UNLOCK_BLOCKED) { - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; - - /* - * Remove this task from the list it blocked on. The - * task can migrate while we acquire the lock, but at - * most one time. So at most two passes through loop. - */ - for (;;) { - rnp = t->rcu_blocked_node; - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - if (rnp == t->rcu_blocked_node) - break; - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - } - empty = !rcu_preempt_blocked_readers_cgp(rnp); - empty_exp = !rcu_preempted_readers_exp(rnp); - smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ - np = rcu_next_node_entry(t, rnp); - list_del_init(&t->rcu_node_entry); - t->rcu_blocked_node = NULL; - trace_rcu_unlock_preempted_task("rcu_preempt", - rnp->gpnum, t->pid); - if (&t->rcu_node_entry == rnp->gp_tasks) - rnp->gp_tasks = np; - if (&t->rcu_node_entry == rnp->exp_tasks) - rnp->exp_tasks = np; -#ifdef CONFIG_RCU_BOOST - if (&t->rcu_node_entry == rnp->boost_tasks) - rnp->boost_tasks = np; - /* Snapshot/clear ->rcu_boost_mutex with rcu_node lock held. */ - if (t->rcu_boost_mutex) { - rbmp = t->rcu_boost_mutex; - t->rcu_boost_mutex = NULL; - } -#endif /* #ifdef CONFIG_RCU_BOOST */ - - /* - * If this was the last task on the current list, and if - * we aren't waiting on any CPUs, report the quiescent state. - * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, - * so we must take a snapshot of the expedited state. - */ - empty_exp_now = !rcu_preempted_readers_exp(rnp); - if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { - trace_rcu_quiescent_state_report("preempt_rcu", - rnp->gpnum, - 0, rnp->qsmask, - rnp->level, - rnp->grplo, - rnp->grphi, - !!rnp->gp_tasks); - rcu_report_unblock_qs_rnp(rnp, flags); - } else { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } - -#ifdef CONFIG_RCU_BOOST - /* Unboost if we were boosted. */ - if (rbmp) - rt_mutex_unlock(rbmp); -#endif /* #ifdef CONFIG_RCU_BOOST */ - - /* - * If this was the last task on the expedited lists, - * then we need to report up the rcu_node hierarchy. - */ - if (!empty_exp && empty_exp_now) - rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); - } else { - local_irq_restore(flags); - } -} - -#ifdef CONFIG_RCU_CPU_STALL_VERBOSE - -/* - * Dump detailed information for all tasks blocking the current RCU - * grace period on the specified rcu_node structure. - */ -static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) -{ - unsigned long flags; - struct task_struct *t; - - raw_spin_lock_irqsave(&rnp->lock, flags); - if (!rcu_preempt_blocked_readers_cgp(rnp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - t = list_entry(rnp->gp_tasks, - struct task_struct, rcu_node_entry); - list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) - sched_show_task(t); - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Dump detailed information for all tasks blocking the current RCU - * grace period. - */ -static void rcu_print_detail_task_stall(struct rcu_state *rsp) -{ - struct rcu_node *rnp = rcu_get_root(rsp); - - rcu_print_detail_task_stall_rnp(rnp); - rcu_for_each_leaf_node(rsp, rnp) - rcu_print_detail_task_stall_rnp(rnp); -} - -#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ - -static void rcu_print_detail_task_stall(struct rcu_state *rsp) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ - -#ifdef CONFIG_RCU_CPU_STALL_INFO - -static void rcu_print_task_stall_begin(struct rcu_node *rnp) -{ - printk(KERN_ERR "\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", - rnp->level, rnp->grplo, rnp->grphi); -} - -static void rcu_print_task_stall_end(void) -{ - printk(KERN_CONT "\n"); -} - -#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ - -static void rcu_print_task_stall_begin(struct rcu_node *rnp) -{ -} - -static void rcu_print_task_stall_end(void) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ - -/* - * Scan the current list of tasks blocked within RCU read-side critical - * sections, printing out the tid of each. - */ -static int rcu_print_task_stall(struct rcu_node *rnp) -{ - struct task_struct *t; - int ndetected = 0; - - if (!rcu_preempt_blocked_readers_cgp(rnp)) - return 0; - rcu_print_task_stall_begin(rnp); - t = list_entry(rnp->gp_tasks, - struct task_struct, rcu_node_entry); - list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { - printk(KERN_CONT " P%d", t->pid); - ndetected++; - } - rcu_print_task_stall_end(); - return ndetected; -} - -/* - * Check that the list of blocked tasks for the newly completed grace - * period is in fact empty. It is a serious bug to complete a grace - * period that still has RCU readers blocked! This function must be - * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock - * must be held by the caller. - * - * Also, if there are blocked tasks on the list, they automatically - * block the newly created grace period, so set up ->gp_tasks accordingly. - */ -static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) -{ - WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); - if (!list_empty(&rnp->blkd_tasks)) - rnp->gp_tasks = rnp->blkd_tasks.next; - WARN_ON_ONCE(rnp->qsmask); -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Handle tasklist migration for case in which all CPUs covered by the - * specified rcu_node have gone offline. Move them up to the root - * rcu_node. The reason for not just moving them to the immediate - * parent is to remove the need for rcu_read_unlock_special() to - * make more than two attempts to acquire the target rcu_node's lock. - * Returns true if there were tasks blocking the current RCU grace - * period. - * - * Returns 1 if there was previously a task blocking the current grace - * period on the specified rcu_node structure. - * - * The caller must hold rnp->lock with irqs disabled. - */ -static int rcu_preempt_offline_tasks(struct rcu_state *rsp, - struct rcu_node *rnp, - struct rcu_data *rdp) -{ - struct list_head *lp; - struct list_head *lp_root; - int retval = 0; - struct rcu_node *rnp_root = rcu_get_root(rsp); - struct task_struct *t; - - if (rnp == rnp_root) { - WARN_ONCE(1, "Last CPU thought to be offlined?"); - return 0; /* Shouldn't happen: at least one CPU online. */ - } - - /* If we are on an internal node, complain bitterly. */ - WARN_ON_ONCE(rnp != rdp->mynode); - - /* - * Move tasks up to root rcu_node. Don't try to get fancy for - * this corner-case operation -- just put this node's tasks - * at the head of the root node's list, and update the root node's - * ->gp_tasks and ->exp_tasks pointers to those of this node's, - * if non-NULL. This might result in waiting for more tasks than - * absolutely necessary, but this is a good performance/complexity - * tradeoff. - */ - if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0) - retval |= RCU_OFL_TASKS_NORM_GP; - if (rcu_preempted_readers_exp(rnp)) - retval |= RCU_OFL_TASKS_EXP_GP; - lp = &rnp->blkd_tasks; - lp_root = &rnp_root->blkd_tasks; - while (!list_empty(lp)) { - t = list_entry(lp->next, typeof(*t), rcu_node_entry); - raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ - list_del(&t->rcu_node_entry); - t->rcu_blocked_node = rnp_root; - list_add(&t->rcu_node_entry, lp_root); - if (&t->rcu_node_entry == rnp->gp_tasks) - rnp_root->gp_tasks = rnp->gp_tasks; - if (&t->rcu_node_entry == rnp->exp_tasks) - rnp_root->exp_tasks = rnp->exp_tasks; -#ifdef CONFIG_RCU_BOOST - if (&t->rcu_node_entry == rnp->boost_tasks) - rnp_root->boost_tasks = rnp->boost_tasks; -#endif /* #ifdef CONFIG_RCU_BOOST */ - raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ - } - - rnp->gp_tasks = NULL; - rnp->exp_tasks = NULL; -#ifdef CONFIG_RCU_BOOST - rnp->boost_tasks = NULL; - /* - * In case root is being boosted and leaf was not. Make sure - * that we boost the tasks blocking the current grace period - * in this case. - */ - raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ - if (rnp_root->boost_tasks != NULL && - rnp_root->boost_tasks != rnp_root->gp_tasks && - rnp_root->boost_tasks != rnp_root->exp_tasks) - rnp_root->boost_tasks = rnp_root->gp_tasks; - raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ -#endif /* #ifdef CONFIG_RCU_BOOST */ - - return retval; -} - -#endif /* #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Check for a quiescent state from the current CPU. When a task blocks, - * the task is recorded in the corresponding CPU's rcu_node structure, - * which is checked elsewhere. - * - * Caller must disable hard irqs. - */ -static void rcu_preempt_check_callbacks(int cpu) -{ - struct task_struct *t = current; - - if (t->rcu_read_lock_nesting == 0) { - rcu_preempt_qs(cpu); - return; - } - if (t->rcu_read_lock_nesting > 0 && - per_cpu(rcu_preempt_data, cpu).qs_pending) - t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; -} - -#ifdef CONFIG_RCU_BOOST - -static void rcu_preempt_do_callbacks(void) -{ - rcu_do_batch(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data)); -} - -#endif /* #ifdef CONFIG_RCU_BOOST */ - -/* - * Queue a preemptible-RCU callback for invocation after a grace period. - */ -void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_preempt_state, -1, 0); -} -EXPORT_SYMBOL_GPL(call_rcu); - -/* - * Queue an RCU callback for lazy invocation after a grace period. - * This will likely be later named something like "call_rcu_lazy()", - * but this change will require some way of tagging the lazy RCU - * callbacks in the list of pending callbacks. Until then, this - * function may only be called from __kfree_rcu(). - */ -void kfree_call_rcu(struct rcu_head *head, - void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_preempt_state, -1, 1); -} -EXPORT_SYMBOL_GPL(kfree_call_rcu); - -/** - * synchronize_rcu - wait until a grace period has elapsed. - * - * Control will return to the caller some time after a full grace - * period has elapsed, in other words after all currently executing RCU - * read-side critical sections have completed. Note, however, that - * upon return from synchronize_rcu(), the caller might well be executing - * concurrently with new RCU read-side critical sections that began while - * synchronize_rcu() was waiting. RCU read-side critical sections are - * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. - * - * See the description of synchronize_sched() for more detailed information - * on memory ordering guarantees. - */ -void synchronize_rcu(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() in RCU read-side critical section"); - if (!rcu_scheduler_active) - return; - if (rcu_expedited) - synchronize_rcu_expedited(); - else - wait_rcu_gp(call_rcu); -} -EXPORT_SYMBOL_GPL(synchronize_rcu); - -static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); -static unsigned long sync_rcu_preempt_exp_count; -static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); - -/* - * Return non-zero if there are any tasks in RCU read-side critical - * sections blocking the current preemptible-RCU expedited grace period. - * If there is no preemptible-RCU expedited grace period currently in - * progress, returns zero unconditionally. - */ -static int rcu_preempted_readers_exp(struct rcu_node *rnp) -{ - return rnp->exp_tasks != NULL; -} - -/* - * return non-zero if there is no RCU expedited grace period in progress - * for the specified rcu_node structure, in other words, if all CPUs and - * tasks covered by the specified rcu_node structure have done their bit - * for the current expedited grace period. Works only for preemptible - * RCU -- other RCU implementation use other means. - * - * Caller must hold sync_rcu_preempt_exp_mutex. - */ -static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) -{ - return !rcu_preempted_readers_exp(rnp) && - ACCESS_ONCE(rnp->expmask) == 0; -} - -/* - * Report the exit from RCU read-side critical section for the last task - * that queued itself during or before the current expedited preemptible-RCU - * grace period. This event is reported either to the rcu_node structure on - * which the task was queued or to one of that rcu_node structure's ancestors, - * recursively up the tree. (Calm down, calm down, we do the recursion - * iteratively!) - * - * Most callers will set the "wake" flag, but the task initiating the - * expedited grace period need not wake itself. - * - * Caller must hold sync_rcu_preempt_exp_mutex. - */ -static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, - bool wake) -{ - unsigned long flags; - unsigned long mask; - - raw_spin_lock_irqsave(&rnp->lock, flags); - for (;;) { - if (!sync_rcu_preempt_exp_done(rnp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - break; - } - if (rnp->parent == NULL) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - if (wake) - wake_up(&sync_rcu_preempt_exp_wq); - break; - } - mask = rnp->grpmask; - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ - rnp = rnp->parent; - raw_spin_lock(&rnp->lock); /* irqs already disabled */ - rnp->expmask &= ~mask; - } -} - -/* - * Snapshot the tasks blocking the newly started preemptible-RCU expedited - * grace period for the specified rcu_node structure. If there are no such - * tasks, report it up the rcu_node hierarchy. - * - * Caller must hold sync_rcu_preempt_exp_mutex and must exclude - * CPU hotplug operations. - */ -static void -sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) -{ - unsigned long flags; - int must_wait = 0; - - raw_spin_lock_irqsave(&rnp->lock, flags); - if (list_empty(&rnp->blkd_tasks)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } else { - rnp->exp_tasks = rnp->blkd_tasks.next; - rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ - must_wait = 1; - } - if (!must_wait) - rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ -} - -/** - * synchronize_rcu_expedited - Brute-force RCU grace period - * - * Wait for an RCU-preempt grace period, but expedite it. The basic - * idea is to invoke synchronize_sched_expedited() to push all the tasks to - * the ->blkd_tasks lists and wait for this list to drain. 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_rcu_expedited() in a loop, - * please restructure your code to batch your updates, and then Use a - * single synchronize_rcu() 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. - */ -void synchronize_rcu_expedited(void) -{ - unsigned long flags; - struct rcu_node *rnp; - struct rcu_state *rsp = &rcu_preempt_state; - unsigned long snap; - int trycount = 0; - - smp_mb(); /* Caller's modifications seen first by other CPUs. */ - snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; - smp_mb(); /* Above access cannot bleed into critical section. */ - - /* - * Block CPU-hotplug operations. This means that any CPU-hotplug - * operation that finds an rcu_node structure with tasks in the - * process of being boosted will know that all tasks blocking - * this expedited grace period will already be in the process of - * being boosted. This simplifies the process of moving tasks - * from leaf to root rcu_node structures. - */ - get_online_cpus(); - - /* - * Acquire lock, falling back to synchronize_rcu() if too many - * lock-acquisition failures. Of course, if someone does the - * expedited grace period for us, just leave. - */ - while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { - if (ULONG_CMP_LT(snap, - ACCESS_ONCE(sync_rcu_preempt_exp_count))) { - put_online_cpus(); - goto mb_ret; /* Others did our work for us. */ - } - if (trycount++ < 10) { - udelay(trycount * num_online_cpus()); - } else { - put_online_cpus(); - wait_rcu_gp(call_rcu); - return; - } - } - if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { - put_online_cpus(); - goto unlock_mb_ret; /* Others did our work for us. */ - } - - /* force all RCU readers onto ->blkd_tasks lists. */ - synchronize_sched_expedited(); - - /* Initialize ->expmask for all non-leaf rcu_node structures. */ - rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { - raw_spin_lock_irqsave(&rnp->lock, flags); - rnp->expmask = rnp->qsmaskinit; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } - - /* Snapshot current state of ->blkd_tasks lists. */ - rcu_for_each_leaf_node(rsp, rnp) - sync_rcu_preempt_exp_init(rsp, rnp); - if (NUM_RCU_NODES > 1) - sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); - - put_online_cpus(); - - /* Wait for snapshotted ->blkd_tasks lists to drain. */ - rnp = rcu_get_root(rsp); - wait_event(sync_rcu_preempt_exp_wq, - sync_rcu_preempt_exp_done(rnp)); - - /* Clean up and exit. */ - smp_mb(); /* ensure expedited GP seen before counter increment. */ - ACCESS_ONCE(sync_rcu_preempt_exp_count)++; -unlock_mb_ret: - mutex_unlock(&sync_rcu_preempt_exp_mutex); -mb_ret: - smp_mb(); /* ensure subsequent action seen after grace period. */ -} -EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - -/** - * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. - * - * Note that this primitive does not necessarily wait for an RCU grace period - * to complete. For example, if there are no RCU callbacks queued anywhere - * in the system, then rcu_barrier() is within its rights to return - * immediately, without waiting for anything, much less an RCU grace period. - */ -void rcu_barrier(void) -{ - _rcu_barrier(&rcu_preempt_state); -} -EXPORT_SYMBOL_GPL(rcu_barrier); - -/* - * Initialize preemptible RCU's state structures. - */ -static void __init __rcu_init_preempt(void) -{ - rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); -} - -#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ - -static struct rcu_state *rcu_state = &rcu_sched_state; - -/* - * Tell them what RCU they are running. - */ -static void __init rcu_bootup_announce(void) -{ - printk(KERN_INFO "Hierarchical RCU implementation.\n"); - rcu_bootup_announce_oddness(); -} - -/* - * Return the number of RCU batches processed thus far for debug & stats. - */ -long rcu_batches_completed(void) -{ - return rcu_batches_completed_sched(); -} -EXPORT_SYMBOL_GPL(rcu_batches_completed); - -/* - * Force a quiescent state for RCU, which, because there is no preemptible - * RCU, becomes the same as rcu-sched. - */ -void rcu_force_quiescent_state(void) -{ - rcu_sched_force_quiescent_state(); -} -EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); - -/* - * Because preemptible RCU does not exist, we never have to check for - * CPUs being in quiescent states. - */ -static void rcu_preempt_note_context_switch(int cpu) -{ -} - -/* - * Because preemptible RCU does not exist, there are never any preempted - * RCU readers. - */ -static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) -{ - return 0; -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* Because preemptible RCU does not exist, no quieting of tasks. */ -static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) -{ - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -#endif /* #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Because preemptible RCU does not exist, we never have to check for - * tasks blocked within RCU read-side critical sections. - */ -static void rcu_print_detail_task_stall(struct rcu_state *rsp) -{ -} - -/* - * Because preemptible RCU does not exist, we never have to check for - * tasks blocked within RCU read-side critical sections. - */ -static int rcu_print_task_stall(struct rcu_node *rnp) -{ - return 0; -} - -/* - * Because there is no preemptible RCU, there can be no readers blocked, - * so there is no need to check for blocked tasks. So check only for - * bogus qsmask values. - */ -static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) -{ - WARN_ON_ONCE(rnp->qsmask); -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Because preemptible RCU does not exist, it never needs to migrate - * tasks that were blocked within RCU read-side critical sections, and - * such non-existent tasks cannot possibly have been blocking the current - * grace period. - */ -static int rcu_preempt_offline_tasks(struct rcu_state *rsp, - struct rcu_node *rnp, - struct rcu_data *rdp) -{ - return 0; -} - -#endif /* #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Because preemptible RCU does not exist, it never has any callbacks - * to check. - */ -static void rcu_preempt_check_callbacks(int cpu) -{ -} - -/* - * Queue an RCU callback for lazy invocation after a grace period. - * This will likely be later named something like "call_rcu_lazy()", - * but this change will require some way of tagging the lazy RCU - * callbacks in the list of pending callbacks. Until then, this - * function may only be called from __kfree_rcu(). - * - * Because there is no preemptible RCU, we use RCU-sched instead. - */ -void kfree_call_rcu(struct rcu_head *head, - void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_sched_state, -1, 1); -} -EXPORT_SYMBOL_GPL(kfree_call_rcu); - -/* - * Wait for an rcu-preempt grace period, but make it happen quickly. - * But because preemptible RCU does not exist, map to rcu-sched. - */ -void synchronize_rcu_expedited(void) -{ - synchronize_sched_expedited(); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Because preemptible RCU does not exist, there is never any need to - * report on tasks preempted in RCU read-side critical sections during - * expedited RCU grace periods. - */ -static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, - bool wake) -{ -} - -#endif /* #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Because preemptible RCU does not exist, rcu_barrier() is just - * another name for rcu_barrier_sched(). - */ -void rcu_barrier(void) -{ - rcu_barrier_sched(); -} -EXPORT_SYMBOL_GPL(rcu_barrier); - -/* - * Because preemptible RCU does not exist, it need not be initialized. - */ -static void __init __rcu_init_preempt(void) -{ -} - -#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ - -#ifdef CONFIG_RCU_BOOST - -#include "rtmutex_common.h" - -#ifdef CONFIG_RCU_TRACE - -static void rcu_initiate_boost_trace(struct rcu_node *rnp) -{ - if (list_empty(&rnp->blkd_tasks)) - rnp->n_balk_blkd_tasks++; - else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) - rnp->n_balk_exp_gp_tasks++; - else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) - rnp->n_balk_boost_tasks++; - else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) - rnp->n_balk_notblocked++; - else if (rnp->gp_tasks != NULL && - ULONG_CMP_LT(jiffies, rnp->boost_time)) - rnp->n_balk_notyet++; - else - rnp->n_balk_nos++; -} - -#else /* #ifdef CONFIG_RCU_TRACE */ - -static void rcu_initiate_boost_trace(struct rcu_node *rnp) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_TRACE */ - -static void rcu_wake_cond(struct task_struct *t, int status) -{ - /* - * If the thread is yielding, only wake it when this - * is invoked from idle - */ - if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) - wake_up_process(t); -} - -/* - * Carry out RCU priority boosting on the task indicated by ->exp_tasks - * or ->boost_tasks, advancing the pointer to the next task in the - * ->blkd_tasks list. - * - * Note that irqs must be enabled: boosting the task can block. - * Returns 1 if there are more tasks needing to be boosted. - */ -static int rcu_boost(struct rcu_node *rnp) -{ - unsigned long flags; - struct rt_mutex mtx; - struct task_struct *t; - struct list_head *tb; - - if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) - return 0; /* Nothing left to boost. */ - - raw_spin_lock_irqsave(&rnp->lock, flags); - - /* - * Recheck under the lock: all tasks in need of boosting - * might exit their RCU read-side critical sections on their own. - */ - if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return 0; - } - - /* - * Preferentially boost tasks blocking expedited grace periods. - * This cannot starve the normal grace periods because a second - * expedited grace period must boost all blocked tasks, including - * those blocking the pre-existing normal grace period. - */ - if (rnp->exp_tasks != NULL) { - tb = rnp->exp_tasks; - rnp->n_exp_boosts++; - } else { - tb = rnp->boost_tasks; - rnp->n_normal_boosts++; - } - rnp->n_tasks_boosted++; - - /* - * We boost task t by manufacturing an rt_mutex that appears to - * be held by task t. We leave a pointer to that rt_mutex where - * task t can find it, and task t will release the mutex when it - * exits its outermost RCU read-side critical section. Then - * simply acquiring this artificial rt_mutex will boost task - * t's priority. (Thanks to tglx for suggesting this approach!) - * - * Note that task t must acquire rnp->lock to remove itself from - * the ->blkd_tasks list, which it will do from exit() if from - * nowhere else. We therefore are guaranteed that task t will - * stay around at least until we drop rnp->lock. Note that - * rnp->lock also resolves races between our priority boosting - * and task t's exiting its outermost RCU read-side critical - * section. - */ - t = container_of(tb, struct task_struct, rcu_node_entry); - rt_mutex_init_proxy_locked(&mtx, t); - t->rcu_boost_mutex = &mtx; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ - rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ - - return ACCESS_ONCE(rnp->exp_tasks) != NULL || - ACCESS_ONCE(rnp->boost_tasks) != NULL; -} - -/* - * Priority-boosting kthread. One per leaf rcu_node and one for the - * root rcu_node. - */ -static int rcu_boost_kthread(void *arg) -{ - struct rcu_node *rnp = (struct rcu_node *)arg; - int spincnt = 0; - int more2boost; - - trace_rcu_utilization("Start boost kthread@init"); - for (;;) { - rnp->boost_kthread_status = RCU_KTHREAD_WAITING; - trace_rcu_utilization("End boost kthread@rcu_wait"); - rcu_wait(rnp->boost_tasks || rnp->exp_tasks); - trace_rcu_utilization("Start boost kthread@rcu_wait"); - rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; - more2boost = rcu_boost(rnp); - if (more2boost) - spincnt++; - else - spincnt = 0; - if (spincnt > 10) { - rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; - trace_rcu_utilization("End boost kthread@rcu_yield"); - schedule_timeout_interruptible(2); - trace_rcu_utilization("Start boost kthread@rcu_yield"); - spincnt = 0; - } - } - /* NOTREACHED */ - trace_rcu_utilization("End boost kthread@notreached"); - return 0; -} - -/* - * Check to see if it is time to start boosting RCU readers that are - * blocking the current grace period, and, if so, tell the per-rcu_node - * kthread to start boosting them. If there is an expedited grace - * period in progress, it is always time to boost. - * - * The caller must hold rnp->lock, which this function releases. - * The ->boost_kthread_task is immortal, so we don't need to worry - * about it going away. - */ -static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) -{ - struct task_struct *t; - - if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { - rnp->n_balk_exp_gp_tasks++; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - if (rnp->exp_tasks != NULL || - (rnp->gp_tasks != NULL && - rnp->boost_tasks == NULL && - rnp->qsmask == 0 && - ULONG_CMP_GE(jiffies, rnp->boost_time))) { - if (rnp->exp_tasks == NULL) - rnp->boost_tasks = rnp->gp_tasks; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - t = rnp->boost_kthread_task; - if (t) - rcu_wake_cond(t, rnp->boost_kthread_status); - } else { - rcu_initiate_boost_trace(rnp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } -} - -/* - * Wake up the per-CPU kthread to invoke RCU callbacks. - */ -static void invoke_rcu_callbacks_kthread(void) -{ - unsigned long flags; - - local_irq_save(flags); - __this_cpu_write(rcu_cpu_has_work, 1); - if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && - current != __this_cpu_read(rcu_cpu_kthread_task)) { - rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), - __this_cpu_read(rcu_cpu_kthread_status)); - } - local_irq_restore(flags); -} - -/* - * Is the current CPU running the RCU-callbacks kthread? - * Caller must have preemption disabled. - */ -static bool rcu_is_callbacks_kthread(void) -{ - return __get_cpu_var(rcu_cpu_kthread_task) == current; -} - -#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) - -/* - * Do priority-boost accounting for the start of a new grace period. - */ -static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) -{ - rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; -} - -/* - * Create an RCU-boost kthread for the specified node if one does not - * already exist. We only create this kthread for preemptible RCU. - * Returns zero if all is well, a negated errno otherwise. - */ -static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, - struct rcu_node *rnp) -{ - int rnp_index = rnp - &rsp->node[0]; - unsigned long flags; - struct sched_param sp; - struct task_struct *t; - - if (&rcu_preempt_state != rsp) - return 0; - - if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) - return 0; - - rsp->boost = 1; - if (rnp->boost_kthread_task != NULL) - return 0; - t = kthread_create(rcu_boost_kthread, (void *)rnp, - "rcub/%d", rnp_index); - if (IS_ERR(t)) - return PTR_ERR(t); - raw_spin_lock_irqsave(&rnp->lock, flags); - rnp->boost_kthread_task = t; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - sp.sched_priority = RCU_BOOST_PRIO; - sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); - wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ - return 0; -} - -static void rcu_kthread_do_work(void) -{ - rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data)); - rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); - rcu_preempt_do_callbacks(); -} - -static void rcu_cpu_kthread_setup(unsigned int cpu) -{ - struct sched_param sp; - - sp.sched_priority = RCU_KTHREAD_PRIO; - sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); -} - -static void rcu_cpu_kthread_park(unsigned int cpu) -{ - per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; -} - -static int rcu_cpu_kthread_should_run(unsigned int cpu) -{ - return __get_cpu_var(rcu_cpu_has_work); -} - -/* - * Per-CPU kernel thread that invokes RCU callbacks. This replaces the - * RCU softirq used in flavors and configurations of RCU that do not - * support RCU priority boosting. - */ -static void rcu_cpu_kthread(unsigned int cpu) -{ - unsigned int *statusp = &__get_cpu_var(rcu_cpu_kthread_status); - char work, *workp = &__get_cpu_var(rcu_cpu_has_work); - int spincnt; - - for (spincnt = 0; spincnt < 10; spincnt++) { - trace_rcu_utilization("Start CPU kthread@rcu_wait"); - local_bh_disable(); - *statusp = RCU_KTHREAD_RUNNING; - this_cpu_inc(rcu_cpu_kthread_loops); - local_irq_disable(); - work = *workp; - *workp = 0; - local_irq_enable(); - if (work) - rcu_kthread_do_work(); - local_bh_enable(); - if (*workp == 0) { - trace_rcu_utilization("End CPU kthread@rcu_wait"); - *statusp = RCU_KTHREAD_WAITING; - return; - } - } - *statusp = RCU_KTHREAD_YIELDING; - trace_rcu_utilization("Start CPU kthread@rcu_yield"); - schedule_timeout_interruptible(2); - trace_rcu_utilization("End CPU kthread@rcu_yield"); - *statusp = RCU_KTHREAD_WAITING; -} - -/* - * Set the per-rcu_node kthread's affinity to cover all CPUs that are - * served by the rcu_node in question. The CPU hotplug lock is still - * held, so the value of rnp->qsmaskinit will be stable. - * - * We don't include outgoingcpu in the affinity set, use -1 if there is - * no outgoing CPU. If there are no CPUs left in the affinity set, - * this function allows the kthread to execute on any CPU. - */ -static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) -{ - struct task_struct *t = rnp->boost_kthread_task; - unsigned long mask = rnp->qsmaskinit; - cpumask_var_t cm; - int cpu; - - if (!t) - return; - if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) - return; - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) - if ((mask & 0x1) && cpu != outgoingcpu) - cpumask_set_cpu(cpu, cm); - if (cpumask_weight(cm) == 0) { - cpumask_setall(cm); - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) - cpumask_clear_cpu(cpu, cm); - WARN_ON_ONCE(cpumask_weight(cm) == 0); - } - set_cpus_allowed_ptr(t, cm); - free_cpumask_var(cm); -} - -static struct smp_hotplug_thread rcu_cpu_thread_spec = { - .store = &rcu_cpu_kthread_task, - .thread_should_run = rcu_cpu_kthread_should_run, - .thread_fn = rcu_cpu_kthread, - .thread_comm = "rcuc/%u", - .setup = rcu_cpu_kthread_setup, - .park = rcu_cpu_kthread_park, -}; - -/* - * Spawn all kthreads -- called as soon as the scheduler is running. - */ -static int __init rcu_spawn_kthreads(void) -{ - struct rcu_node *rnp; - int cpu; - - rcu_scheduler_fully_active = 1; - for_each_possible_cpu(cpu) - per_cpu(rcu_cpu_has_work, cpu) = 0; - BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); - rnp = rcu_get_root(rcu_state); - (void)rcu_spawn_one_boost_kthread(rcu_state, rnp); - if (NUM_RCU_NODES > 1) { - rcu_for_each_leaf_node(rcu_state, rnp) - (void)rcu_spawn_one_boost_kthread(rcu_state, rnp); - } - return 0; -} -early_initcall(rcu_spawn_kthreads); - -static void __cpuinit rcu_prepare_kthreads(int cpu) -{ - struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); - struct rcu_node *rnp = rdp->mynode; - - /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ - if (rcu_scheduler_fully_active) - (void)rcu_spawn_one_boost_kthread(rcu_state, rnp); -} - -#else /* #ifdef CONFIG_RCU_BOOST */ - -static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) -{ - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -static void invoke_rcu_callbacks_kthread(void) -{ - WARN_ON_ONCE(1); -} - -static bool rcu_is_callbacks_kthread(void) -{ - return false; -} - -static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) -{ -} - -static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) -{ -} - -static int __init rcu_scheduler_really_started(void) -{ - rcu_scheduler_fully_active = 1; - return 0; -} -early_initcall(rcu_scheduler_really_started); - -static void __cpuinit rcu_prepare_kthreads(int cpu) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_BOOST */ - -#if !defined(CONFIG_RCU_FAST_NO_HZ) - -/* - * 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. This function is part of the RCU implementation; it is -not- - * an exported member of the RCU API. - * - * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs - * any flavor of RCU. - */ -int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) -{ - *delta_jiffies = ULONG_MAX; - return rcu_cpu_has_callbacks(cpu); -} - -/* - * Because we do not have RCU_FAST_NO_HZ, don't bother initializing for it. - */ -static void rcu_prepare_for_idle_init(int cpu) -{ -} - -/* - * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up - * after it. - */ -static void rcu_cleanup_after_idle(int cpu) -{ -} - -/* - * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, - * is nothing. - */ -static void rcu_prepare_for_idle(int cpu) -{ -} - -/* - * Don't bother keeping a running count of the number of RCU callbacks - * posted because CONFIG_RCU_FAST_NO_HZ=n. - */ -static void rcu_idle_count_callbacks_posted(void) -{ -} - -#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ - -/* - * This code is invoked when a CPU goes idle, at which point we want - * to have the CPU do everything required for RCU so that it can enter - * the energy-efficient dyntick-idle mode. This is handled by a - * state machine implemented by rcu_prepare_for_idle() below. - * - * The following three proprocessor symbols control this state machine: - * - * RCU_IDLE_FLUSHES gives the maximum number of times that we will attempt - * to satisfy RCU. Beyond this point, it is better to incur a periodic - * scheduling-clock interrupt than to loop through the state machine - * at full power. - * RCU_IDLE_OPT_FLUSHES gives the number of RCU_IDLE_FLUSHES that are - * optional if RCU does not need anything immediately from this - * CPU, even if this CPU still has RCU callbacks queued. The first - * times through the state machine are mandatory: we need to give - * the state machine a chance to communicate a quiescent state - * to the RCU core. - * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted - * to sleep in dyntick-idle mode with RCU callbacks pending. This - * is sized to be roughly one RCU grace period. Those energy-efficiency - * benchmarkers who might otherwise be tempted to set this to a large - * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your - * system. And if you are -that- concerned about energy efficiency, - * just power the system down and be done with it! - * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is - * permitted to sleep in dyntick-idle mode with only lazy RCU - * callbacks pending. Setting this too high can OOM your system. - * - * The values below work well in practice. If future workloads require - * adjustment, they can be converted into kernel config parameters, though - * making the state machine smarter might be a better option. - */ -#define RCU_IDLE_FLUSHES 5 /* Number of dyntick-idle tries. */ -#define RCU_IDLE_OPT_FLUSHES 3 /* Optional dyntick-idle tries. */ -#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ -#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ - -extern int tick_nohz_enabled; - -/* - * Does the specified flavor of RCU have non-lazy callbacks pending on - * the specified CPU? Both RCU flavor and CPU are specified by the - * rcu_data structure. - */ -static bool __rcu_cpu_has_nonlazy_callbacks(struct rcu_data *rdp) -{ - return rdp->qlen != rdp->qlen_lazy; -} - -#ifdef CONFIG_TREE_PREEMPT_RCU - -/* - * Are there non-lazy RCU-preempt callbacks? (There cannot be if there - * is no RCU-preempt in the kernel.) - */ -static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); - - return __rcu_cpu_has_nonlazy_callbacks(rdp); -} - -#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ - -static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu) -{ - return 0; -} - -#endif /* else #ifdef CONFIG_TREE_PREEMPT_RCU */ - -/* - * Does any flavor of RCU have non-lazy callbacks on the specified CPU? - */ -static bool rcu_cpu_has_nonlazy_callbacks(int cpu) -{ - return __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_sched_data, cpu)) || - __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_bh_data, cpu)) || - rcu_preempt_cpu_has_nonlazy_callbacks(cpu); -} - -/* - * Allow the CPU to enter dyntick-idle mode if either: (1) There are no - * callbacks on this CPU, (2) this CPU has not yet attempted to enter - * dyntick-idle mode, or (3) this CPU is in the process of attempting to - * enter dyntick-idle mode. Otherwise, if we have recently tried and failed - * to enter dyntick-idle mode, we refuse to try to enter it. After all, - * it is better to incur scheduling-clock interrupts than to spin - * continuously for the same time duration! - * - * The delta_jiffies argument is used to store the time when RCU is - * going to need the CPU again if it still has callbacks. The reason - * for this is that rcu_prepare_for_idle() might need to post a timer, - * but if so, it will do so after tick_nohz_stop_sched_tick() has set - * the wakeup time for this CPU. This means that RCU's timer can be - * delayed until the wakeup time, which defeats the purpose of posting - * a timer. - */ -int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) -{ - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - - /* Flag a new idle sojourn to the idle-entry state machine. */ - rdtp->idle_first_pass = 1; - /* If no callbacks, RCU doesn't need the CPU. */ - if (!rcu_cpu_has_callbacks(cpu)) { - *delta_jiffies = ULONG_MAX; - return 0; - } - if (rdtp->dyntick_holdoff == jiffies) { - /* RCU recently tried and failed, so don't try again. */ - *delta_jiffies = 1; - return 1; - } - /* Set up for the possibility that RCU will post a timer. */ - if (rcu_cpu_has_nonlazy_callbacks(cpu)) { - *delta_jiffies = round_up(RCU_IDLE_GP_DELAY + jiffies, - RCU_IDLE_GP_DELAY) - jiffies; - } else { - *delta_jiffies = jiffies + RCU_IDLE_LAZY_GP_DELAY; - *delta_jiffies = round_jiffies(*delta_jiffies) - jiffies; - } - return 0; -} - -/* - * Handler for smp_call_function_single(). The only point of this - * handler is to wake the CPU up, so the handler does only tracing. - */ -void rcu_idle_demigrate(void *unused) -{ - trace_rcu_prep_idle("Demigrate"); -} - -/* - * Timer handler used to force CPU to start pushing its remaining RCU - * callbacks in the case where it entered dyntick-idle mode with callbacks - * pending. The hander doesn't really need to do anything because the - * real work is done upon re-entry to idle, or by the next scheduling-clock - * interrupt should idle not be re-entered. - * - * One special case: the timer gets migrated without awakening the CPU - * on which the timer was scheduled on. In this case, we must wake up - * that CPU. We do so with smp_call_function_single(). - */ -static void rcu_idle_gp_timer_func(unsigned long cpu_in) -{ - int cpu = (int)cpu_in; - - trace_rcu_prep_idle("Timer"); - if (cpu != smp_processor_id()) - smp_call_function_single(cpu, rcu_idle_demigrate, NULL, 0); - else - WARN_ON_ONCE(1); /* Getting here can hang the system... */ -} - -/* - * Initialize the timer used to pull CPUs out of dyntick-idle mode. - */ -static void rcu_prepare_for_idle_init(int cpu) -{ - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - - rdtp->dyntick_holdoff = jiffies - 1; - setup_timer(&rdtp->idle_gp_timer, rcu_idle_gp_timer_func, cpu); - rdtp->idle_gp_timer_expires = jiffies - 1; - rdtp->idle_first_pass = 1; -} - -/* - * Clean up for exit from idle. Because we are exiting from idle, there - * is no longer any point to ->idle_gp_timer, so cancel it. This will - * do nothing if this timer is not active, so just cancel it unconditionally. - */ -static void rcu_cleanup_after_idle(int cpu) -{ - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - - del_timer(&rdtp->idle_gp_timer); - trace_rcu_prep_idle("Cleanup after idle"); - rdtp->tick_nohz_enabled_snap = ACCESS_ONCE(tick_nohz_enabled); -} - -/* - * Check to see if any RCU-related work can be done by the current CPU, - * and if so, schedule a softirq to get it done. This function is part - * of the RCU implementation; it is -not- an exported member of the RCU API. - * - * The idea is for the current CPU to clear out all work required by the - * RCU core for the current grace period, so that this CPU can be permitted - * to enter dyntick-idle mode. In some cases, it will need to be awakened - * at the end of the grace period by whatever CPU ends the grace period. - * This allows CPUs to go dyntick-idle more quickly, and to reduce the - * number of wakeups by a modest integer factor. - * - * Because it is not legal to invoke rcu_process_callbacks() with irqs - * disabled, we do one pass of force_quiescent_state(), then do a - * invoke_rcu_core() to cause rcu_process_callbacks() to be invoked - * later. The ->dyntick_drain field controls the sequencing. - * - * The caller must have disabled interrupts. - */ -static void rcu_prepare_for_idle(int cpu) -{ - struct timer_list *tp; - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - int tne; - - /* Handle nohz enablement switches conservatively. */ - tne = ACCESS_ONCE(tick_nohz_enabled); - if (tne != rdtp->tick_nohz_enabled_snap) { - if (rcu_cpu_has_callbacks(cpu)) - invoke_rcu_core(); /* force nohz to see update. */ - rdtp->tick_nohz_enabled_snap = tne; - return; - } - if (!tne) - return; - - /* Adaptive-tick mode, where usermode execution is idle to RCU. */ - if (!is_idle_task(current)) { - rdtp->dyntick_holdoff = jiffies - 1; - if (rcu_cpu_has_nonlazy_callbacks(cpu)) { - trace_rcu_prep_idle("User dyntick with callbacks"); - rdtp->idle_gp_timer_expires = - round_up(jiffies + RCU_IDLE_GP_DELAY, - RCU_IDLE_GP_DELAY); - } else if (rcu_cpu_has_callbacks(cpu)) { - rdtp->idle_gp_timer_expires = - round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY); - trace_rcu_prep_idle("User dyntick with lazy callbacks"); - } else { - return; - } - tp = &rdtp->idle_gp_timer; - mod_timer_pinned(tp, rdtp->idle_gp_timer_expires); - return; - } - - /* - * If this is an idle re-entry, for example, due to use of - * RCU_NONIDLE() or the new idle-loop tracing API within the idle - * loop, then don't take any state-machine actions, unless the - * momentary exit from idle queued additional non-lazy callbacks. - * Instead, repost the ->idle_gp_timer if this CPU has callbacks - * pending. - */ - if (!rdtp->idle_first_pass && - (rdtp->nonlazy_posted == rdtp->nonlazy_posted_snap)) { - if (rcu_cpu_has_callbacks(cpu)) { - tp = &rdtp->idle_gp_timer; - mod_timer_pinned(tp, rdtp->idle_gp_timer_expires); - } - return; - } - rdtp->idle_first_pass = 0; - rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted - 1; - - /* - * If there are no callbacks on this CPU, enter dyntick-idle mode. - * Also reset state to avoid prejudicing later attempts. - */ - if (!rcu_cpu_has_callbacks(cpu)) { - rdtp->dyntick_holdoff = jiffies - 1; - rdtp->dyntick_drain = 0; - trace_rcu_prep_idle("No callbacks"); - return; - } - - /* - * If in holdoff mode, just return. We will presumably have - * refrained from disabling the scheduling-clock tick. - */ - if (rdtp->dyntick_holdoff == jiffies) { - trace_rcu_prep_idle("In holdoff"); - return; - } - - /* Check and update the ->dyntick_drain sequencing. */ - if (rdtp->dyntick_drain <= 0) { - /* First time through, initialize the counter. */ - rdtp->dyntick_drain = RCU_IDLE_FLUSHES; - } else if (rdtp->dyntick_drain <= RCU_IDLE_OPT_FLUSHES && - !rcu_pending(cpu) && - !local_softirq_pending()) { - /* Can we go dyntick-idle despite still having callbacks? */ - rdtp->dyntick_drain = 0; - rdtp->dyntick_holdoff = jiffies; - if (rcu_cpu_has_nonlazy_callbacks(cpu)) { - trace_rcu_prep_idle("Dyntick with callbacks"); - rdtp->idle_gp_timer_expires = - round_up(jiffies + RCU_IDLE_GP_DELAY, - RCU_IDLE_GP_DELAY); - } else { - rdtp->idle_gp_timer_expires = - round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY); - trace_rcu_prep_idle("Dyntick with lazy callbacks"); - } - tp = &rdtp->idle_gp_timer; - mod_timer_pinned(tp, rdtp->idle_gp_timer_expires); - rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; - return; /* Nothing more to do immediately. */ - } else if (--(rdtp->dyntick_drain) <= 0) { - /* We have hit the limit, so time to give up. */ - rdtp->dyntick_holdoff = jiffies; - trace_rcu_prep_idle("Begin holdoff"); - invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */ - return; - } - - /* - * Do one step of pushing the remaining RCU callbacks through - * the RCU core state machine. - */ -#ifdef CONFIG_TREE_PREEMPT_RCU - if (per_cpu(rcu_preempt_data, cpu).nxtlist) { - rcu_preempt_qs(cpu); - force_quiescent_state(&rcu_preempt_state); - } -#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ - if (per_cpu(rcu_sched_data, cpu).nxtlist) { - rcu_sched_qs(cpu); - force_quiescent_state(&rcu_sched_state); - } - if (per_cpu(rcu_bh_data, cpu).nxtlist) { - rcu_bh_qs(cpu); - force_quiescent_state(&rcu_bh_state); - } - - /* - * If RCU callbacks are still pending, RCU still needs this CPU. - * So try forcing the callbacks through the grace period. - */ - if (rcu_cpu_has_callbacks(cpu)) { - trace_rcu_prep_idle("More callbacks"); - invoke_rcu_core(); - } else { - trace_rcu_prep_idle("Callbacks drained"); - } -} - -/* - * Keep a running count of the number of non-lazy callbacks posted - * on this CPU. This running counter (which is never decremented) allows - * rcu_prepare_for_idle() to detect when something out of the idle loop - * posts a callback, even if an equal number of callbacks are invoked. - * Of course, callbacks should only be posted from within a trace event - * designed to be called from idle or from within RCU_NONIDLE(). - */ -static void rcu_idle_count_callbacks_posted(void) -{ - __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); -} - -/* - * Data for flushing lazy RCU callbacks at OOM time. - */ -static atomic_t oom_callback_count; -static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); - -/* - * RCU OOM callback -- decrement the outstanding count and deliver the - * wake-up if we are the last one. - */ -static void rcu_oom_callback(struct rcu_head *rhp) -{ - if (atomic_dec_and_test(&oom_callback_count)) - wake_up(&oom_callback_wq); -} - -/* - * Post an rcu_oom_notify callback on the current CPU if it has at - * least one lazy callback. This will unnecessarily post callbacks - * to CPUs that already have a non-lazy callback at the end of their - * callback list, but this is an infrequent operation, so accept some - * extra overhead to keep things simple. - */ -static void rcu_oom_notify_cpu(void *unused) -{ - struct rcu_state *rsp; - struct rcu_data *rdp; - - for_each_rcu_flavor(rsp) { - rdp = __this_cpu_ptr(rsp->rda); - if (rdp->qlen_lazy != 0) { - atomic_inc(&oom_callback_count); - rsp->call(&rdp->oom_head, rcu_oom_callback); - } - } -} - -/* - * If low on memory, ensure that each CPU has a non-lazy callback. - * This will wake up CPUs that have only lazy callbacks, in turn - * ensuring that they free up the corresponding memory in a timely manner. - * Because an uncertain amount of memory will be freed in some uncertain - * timeframe, we do not claim to have freed anything. - */ -static int rcu_oom_notify(struct notifier_block *self, - unsigned long notused, void *nfreed) -{ - int cpu; - - /* Wait for callbacks from earlier instance to complete. */ - wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); - - /* - * Prevent premature wakeup: ensure that all increments happen - * before there is a chance of the counter reaching zero. - */ - atomic_set(&oom_callback_count, 1); - - get_online_cpus(); - for_each_online_cpu(cpu) { - smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); - cond_resched(); - } - put_online_cpus(); - - /* Unconditionally decrement: no need to wake ourselves up. */ - atomic_dec(&oom_callback_count); - - return NOTIFY_OK; -} - -static struct notifier_block rcu_oom_nb = { - .notifier_call = rcu_oom_notify -}; - -static int __init rcu_register_oom_notifier(void) -{ - register_oom_notifier(&rcu_oom_nb); - return 0; -} -early_initcall(rcu_register_oom_notifier); - -#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ - -#ifdef CONFIG_RCU_CPU_STALL_INFO - -#ifdef CONFIG_RCU_FAST_NO_HZ - -static void print_cpu_stall_fast_no_hz(char *cp, int cpu) -{ - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - struct timer_list *tltp = &rdtp->idle_gp_timer; - char c; - - c = rdtp->dyntick_holdoff == jiffies ? 'H' : '.'; - if (timer_pending(tltp)) - sprintf(cp, "drain=%d %c timer=%lu", - rdtp->dyntick_drain, c, tltp->expires - jiffies); - else - sprintf(cp, "drain=%d %c timer not pending", - rdtp->dyntick_drain, c); -} - -#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ - -static void print_cpu_stall_fast_no_hz(char *cp, int cpu) -{ - *cp = '\0'; -} - -#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ - -/* Initiate the stall-info list. */ -static void print_cpu_stall_info_begin(void) -{ - printk(KERN_CONT "\n"); -} - -/* - * Print out diagnostic information for the specified stalled CPU. - * - * If the specified CPU is aware of the current RCU grace period - * (flavor specified by rsp), then print the number of scheduling - * clock interrupts the CPU has taken during the time that it has - * been aware. Otherwise, print the number of RCU grace periods - * that this CPU is ignorant of, for example, "1" if the CPU was - * aware of the previous grace period. - * - * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. - */ -static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) -{ - char fast_no_hz[72]; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_dynticks *rdtp = rdp->dynticks; - char *ticks_title; - unsigned long ticks_value; - - if (rsp->gpnum == rdp->gpnum) { - ticks_title = "ticks this GP"; - ticks_value = rdp->ticks_this_gp; - } else { - ticks_title = "GPs behind"; - ticks_value = rsp->gpnum - rdp->gpnum; - } - print_cpu_stall_fast_no_hz(fast_no_hz, cpu); - printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d %s\n", - cpu, ticks_value, ticks_title, - atomic_read(&rdtp->dynticks) & 0xfff, - rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, - fast_no_hz); -} - -/* Terminate the stall-info list. */ -static void print_cpu_stall_info_end(void) -{ - printk(KERN_ERR "\t"); -} - -/* Zero ->ticks_this_gp for all flavors of RCU. */ -static void zero_cpu_stall_ticks(struct rcu_data *rdp) -{ - rdp->ticks_this_gp = 0; -} - -/* Increment ->ticks_this_gp for all flavors of RCU. */ -static void increment_cpu_stall_ticks(void) -{ - struct rcu_state *rsp; - - for_each_rcu_flavor(rsp) - __this_cpu_ptr(rsp->rda)->ticks_this_gp++; -} - -#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ - -static void print_cpu_stall_info_begin(void) -{ - printk(KERN_CONT " {"); -} - -static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) -{ - printk(KERN_CONT " %d", cpu); -} - -static void print_cpu_stall_info_end(void) -{ - printk(KERN_CONT "} "); -} - -static void zero_cpu_stall_ticks(struct rcu_data *rdp) -{ -} - -static void increment_cpu_stall_ticks(void) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ - -#ifdef CONFIG_RCU_NOCB_CPU - -/* - * Offload callback processing from the boot-time-specified set of CPUs - * specified by rcu_nocb_mask. For each CPU in the set, there is a - * kthread created that pulls the callbacks from the corresponding CPU, - * waits for a grace period to elapse, and invokes the callbacks. - * The no-CBs CPUs do a wake_up() on their kthread when they insert - * a callback into any empty list, unless the rcu_nocb_poll boot parameter - * has been specified, in which case each kthread actively polls its - * CPU. (Which isn't so great for energy efficiency, but which does - * reduce RCU's overhead on that CPU.) - * - * This is intended to be used in conjunction with Frederic Weisbecker's - * adaptive-idle work, which would seriously reduce OS jitter on CPUs - * running CPU-bound user-mode computations. - * - * Offloading of callback processing could also in theory be used as - * an energy-efficiency measure because CPUs with no RCU callbacks - * queued are more aggressive about entering dyntick-idle mode. - */ - - -/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ -static int __init rcu_nocb_setup(char *str) -{ - alloc_bootmem_cpumask_var(&rcu_nocb_mask); - have_rcu_nocb_mask = true; - cpulist_parse(str, rcu_nocb_mask); - return 1; -} -__setup("rcu_nocbs=", rcu_nocb_setup); - -/* Is the specified CPU a no-CPUs CPU? */ -static bool is_nocb_cpu(int cpu) -{ - if (have_rcu_nocb_mask) - return cpumask_test_cpu(cpu, rcu_nocb_mask); - return false; -} - -/* - * Enqueue the specified string of rcu_head structures onto the specified - * CPU's no-CBs lists. The CPU is specified by rdp, the head of the - * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy - * counts are supplied by rhcount and rhcount_lazy. - * - * If warranted, also wake up the kthread servicing this CPUs queues. - */ -static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, - struct rcu_head *rhp, - struct rcu_head **rhtp, - int rhcount, int rhcount_lazy) -{ - int len; - struct rcu_head **old_rhpp; - struct task_struct *t; - - /* Enqueue the callback on the nocb list and update counts. */ - old_rhpp = xchg(&rdp->nocb_tail, rhtp); - ACCESS_ONCE(*old_rhpp) = rhp; - atomic_long_add(rhcount, &rdp->nocb_q_count); - atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); - - /* If we are not being polled and there is a kthread, awaken it ... */ - t = ACCESS_ONCE(rdp->nocb_kthread); - if (rcu_nocb_poll | !t) - return; - len = atomic_long_read(&rdp->nocb_q_count); - if (old_rhpp == &rdp->nocb_head) { - wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */ - rdp->qlen_last_fqs_check = 0; - } else if (len > rdp->qlen_last_fqs_check + qhimark) { - wake_up_process(t); /* ... or if many callbacks queued. */ - rdp->qlen_last_fqs_check = LONG_MAX / 2; - } - return; -} - -/* - * This is a helper for __call_rcu(), which invokes this when the normal - * callback queue is inoperable. If this is not a no-CBs CPU, this - * function returns failure back to __call_rcu(), which can complain - * appropriately. - * - * Otherwise, this function queues the callback where the corresponding - * "rcuo" kthread can find it. - */ -static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, - bool lazy) -{ - - if (!is_nocb_cpu(rdp->cpu)) - return 0; - __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy); - return 1; -} - -/* - * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is - * not a no-CBs CPU. - */ -static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, - struct rcu_data *rdp) -{ - long ql = rsp->qlen; - long qll = rsp->qlen_lazy; - - /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ - if (!is_nocb_cpu(smp_processor_id())) - return 0; - rsp->qlen = 0; - rsp->qlen_lazy = 0; - - /* First, enqueue the donelist, if any. This preserves CB ordering. */ - if (rsp->orphan_donelist != NULL) { - __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, - rsp->orphan_donetail, ql, qll); - ql = qll = 0; - rsp->orphan_donelist = NULL; - rsp->orphan_donetail = &rsp->orphan_donelist; - } - if (rsp->orphan_nxtlist != NULL) { - __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, - rsp->orphan_nxttail, ql, qll); - ql = qll = 0; - rsp->orphan_nxtlist = NULL; - rsp->orphan_nxttail = &rsp->orphan_nxtlist; - } - return 1; -} - -/* - * There must be at least one non-no-CBs CPU in operation at any given - * time, because no-CBs CPUs are not capable of initiating grace periods - * independently. This function therefore complains if the specified - * CPU is the last non-no-CBs CPU, allowing the CPU-hotplug system to - * avoid offlining the last such CPU. (Recursion is a wonderful thing, - * but you have to have a base case!) - */ -static bool nocb_cpu_expendable(int cpu) -{ - cpumask_var_t non_nocb_cpus; - int ret; - - /* - * If there are no no-CB CPUs or if this CPU is not a no-CB CPU, - * then offlining this CPU is harmless. Let it happen. - */ - if (!have_rcu_nocb_mask || is_nocb_cpu(cpu)) - return 1; - - /* If no memory, play it safe and keep the CPU around. */ - if (!alloc_cpumask_var(&non_nocb_cpus, GFP_NOIO)) - return 0; - cpumask_andnot(non_nocb_cpus, cpu_online_mask, rcu_nocb_mask); - cpumask_clear_cpu(cpu, non_nocb_cpus); - ret = !cpumask_empty(non_nocb_cpus); - free_cpumask_var(non_nocb_cpus); - return ret; -} - -/* - * Helper structure for remote registry of RCU callbacks. - * This is needed for when a no-CBs CPU needs to start a grace period. - * If it just invokes call_rcu(), the resulting callback will be queued, - * which can result in deadlock. - */ -struct rcu_head_remote { - struct rcu_head *rhp; - call_rcu_func_t *crf; - void (*func)(struct rcu_head *rhp); -}; - -/* - * Register a callback as specified by the rcu_head_remote struct. - * This function is intended to be invoked via smp_call_function_single(). - */ -static void call_rcu_local(void *arg) -{ - struct rcu_head_remote *rhrp = - container_of(arg, struct rcu_head_remote, rhp); - - rhrp->crf(rhrp->rhp, rhrp->func); -} - -/* - * Set up an rcu_head_remote structure and the invoke call_rcu_local() - * on CPU 0 (which is guaranteed to be a non-no-CBs CPU) via - * smp_call_function_single(). - */ -static void invoke_crf_remote(struct rcu_head *rhp, - void (*func)(struct rcu_head *rhp), - call_rcu_func_t crf) -{ - struct rcu_head_remote rhr; - - rhr.rhp = rhp; - rhr.crf = crf; - rhr.func = func; - smp_call_function_single(0, call_rcu_local, &rhr, 1); -} - -/* - * Helper functions to be passed to wait_rcu_gp(), each of which - * invokes invoke_crf_remote() to register a callback appropriately. - */ -static void __maybe_unused -call_rcu_preempt_remote(struct rcu_head *rhp, - void (*func)(struct rcu_head *rhp)) -{ - invoke_crf_remote(rhp, func, call_rcu); -} -static void call_rcu_bh_remote(struct rcu_head *rhp, - void (*func)(struct rcu_head *rhp)) -{ - invoke_crf_remote(rhp, func, call_rcu_bh); -} -static void call_rcu_sched_remote(struct rcu_head *rhp, - void (*func)(struct rcu_head *rhp)) -{ - invoke_crf_remote(rhp, func, call_rcu_sched); -} - -/* - * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes - * callbacks queued by the corresponding no-CBs CPU. - */ -static int rcu_nocb_kthread(void *arg) -{ - int c, cl; - struct rcu_head *list; - struct rcu_head *next; - struct rcu_head **tail; - struct rcu_data *rdp = arg; - - /* Each pass through this loop invokes one batch of callbacks */ - for (;;) { - /* If not polling, wait for next batch of callbacks. */ - if (!rcu_nocb_poll) - wait_event(rdp->nocb_wq, rdp->nocb_head); - list = ACCESS_ONCE(rdp->nocb_head); - if (!list) { - schedule_timeout_interruptible(1); - continue; - } - - /* - * Extract queued callbacks, update counts, and wait - * for a grace period to elapse. - */ - ACCESS_ONCE(rdp->nocb_head) = NULL; - tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); - c = atomic_long_xchg(&rdp->nocb_q_count, 0); - cl = atomic_long_xchg(&rdp->nocb_q_count_lazy, 0); - ACCESS_ONCE(rdp->nocb_p_count) += c; - ACCESS_ONCE(rdp->nocb_p_count_lazy) += cl; - wait_rcu_gp(rdp->rsp->call_remote); - - /* Each pass through the following loop invokes a callback. */ - trace_rcu_batch_start(rdp->rsp->name, cl, c, -1); - c = cl = 0; - while (list) { - next = list->next; - /* Wait for enqueuing to complete, if needed. */ - while (next == NULL && &list->next != tail) { - schedule_timeout_interruptible(1); - next = list->next; - } - debug_rcu_head_unqueue(list); - local_bh_disable(); - if (__rcu_reclaim(rdp->rsp->name, list)) - cl++; - c++; - local_bh_enable(); - list = next; - } - trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); - ACCESS_ONCE(rdp->nocb_p_count) -= c; - ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl; - rdp->n_nocbs_invoked += c; - } - return 0; -} - -/* Initialize per-rcu_data variables for no-CBs CPUs. */ -static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) -{ - rdp->nocb_tail = &rdp->nocb_head; - init_waitqueue_head(&rdp->nocb_wq); -} - -/* Create a kthread for each RCU flavor for each no-CBs CPU. */ -static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp) -{ - int cpu; - struct rcu_data *rdp; - struct task_struct *t; - - if (rcu_nocb_mask == NULL) - return; - for_each_cpu(cpu, rcu_nocb_mask) { - rdp = per_cpu_ptr(rsp->rda, cpu); - t = kthread_run(rcu_nocb_kthread, rdp, "rcuo%d", cpu); - BUG_ON(IS_ERR(t)); - ACCESS_ONCE(rdp->nocb_kthread) = t; - } -} - -/* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ -static void init_nocb_callback_list(struct rcu_data *rdp) -{ - if (rcu_nocb_mask == NULL || - !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) - return; - rdp->nxttail[RCU_NEXT_TAIL] = NULL; -} - -/* Initialize the ->call_remote fields in the rcu_state structures. */ -static void __init rcu_init_nocb(void) -{ -#ifdef CONFIG_PREEMPT_RCU - rcu_preempt_state.call_remote = call_rcu_preempt_remote; -#endif /* #ifdef CONFIG_PREEMPT_RCU */ - rcu_bh_state.call_remote = call_rcu_bh_remote; - rcu_sched_state.call_remote = call_rcu_sched_remote; -} - -#else /* #ifdef CONFIG_RCU_NOCB_CPU */ - -static bool is_nocb_cpu(int cpu) -{ - return false; -} - -static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, - bool lazy) -{ - return 0; -} - -static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, - struct rcu_data *rdp) -{ - return 0; -} - -static bool nocb_cpu_expendable(int cpu) -{ - return 1; -} - -static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) -{ -} - -static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp) -{ -} - -static void init_nocb_callback_list(struct rcu_data *rdp) -{ -} - -static void __init rcu_init_nocb(void) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |