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authorPaul E. McKenney <paul.mckenney@linaro.org>2013-01-07 13:37:42 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-03-12 11:17:51 -0700
commit34ed62461ae4970695974afb9a60ac3df0086830 (patch)
treed65a582953a66ee089074fd5a57e39460d4ce2c6 /kernel/rcutree.h
parentf6161aa153581da4a3867a2d1a7caf4be19b6ec9 (diff)
rcu: Remove restrictions on no-CBs CPUs
Currently, CPU 0 is constrained to not be a no-CBs CPU, and furthermore at least one no-CBs CPU must remain online at any given time. These restrictions are problematic in some situations, such as cases where all CPUs must run a real-time workload that needs to be insulated from OS jitter and latencies due to RCU callback invocation. This commit therefore provides no-CBs CPUs a (very crude and energy-inefficient) way to start and to wait for grace periods independently of the normal RCU callback mechanisms. This approach allows any or all of the CPUs to be designated as no-CBs CPUs, and allows any proper subset of the CPUs (whether no-CBs CPUs or not) to be offlined. This commit also provides a fix for a locking bug spotted by Xie ChanglongX <changlongx.xie@intel.com>. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.h')
-rw-r--r--kernel/rcutree.h12
1 files changed, 3 insertions, 9 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index c896b5045d9..7af39f4aaac 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -326,6 +326,7 @@ struct rcu_data {
int nocb_p_count_lazy; /* (approximate). */
wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
+ bool nocb_needs_gp;
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
int cpu;
@@ -375,12 +376,6 @@ struct rcu_state {
struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
void (*call)(struct rcu_head *head, /* call_rcu() flavor. */
void (*func)(struct rcu_head *head));
-#ifdef CONFIG_RCU_NOCB_CPU
- void (*call_remote)(struct rcu_head *head,
- void (*func)(struct rcu_head *head));
- /* call_rcu() flavor, but for */
- /* placing on remote CPU. */
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
/* The following fields are guarded by the root rcu_node's lock. */
@@ -529,16 +524,15 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
static void print_cpu_stall_info_end(void);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
+static int rcu_nocb_needs_gp(struct rcu_data *rdp);
static bool is_nocb_cpu(int cpu);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy);
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
struct rcu_data *rdp);
-static bool nocb_cpu_expendable(int cpu);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void 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);
+static bool init_nocb_callback_list(struct rcu_data *rdp);
#endif /* #ifndef RCU_TREE_NONCORE */