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rcu: Omit self-awaken when setting up expedited grace period 

When setting up an expedited grace period, if there were no readers, the
task will awaken itself.  This commit removes this useless self-awakening.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Thomas Gleixner 2011-10-22 07:12:34 -07:00 committed by Paul E. McKenney
parent 34240697d6
commit b40d293eb3
3 changed files with 14 additions and 7 deletions
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2
kernel/rcutree.c
View File

@ -1320,7 +1320,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
else else
raw_spin_unlock_irqrestore(&rnp->lock, flags); raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (need_report & RCU_OFL_TASKS_EXP_GP) if (need_report & RCU_OFL_TASKS_EXP_GP)
rcu_report_exp_rnp(rsp, rnp); rcu_report_exp_rnp(rsp, rnp, true);
rcu_node_kthread_setaffinity(rnp, -1); rcu_node_kthread_setaffinity(rnp, -1);
} }

3
kernel/rcutree.h
View File

@ -444,7 +444,8 @@ static void rcu_preempt_check_callbacks(int cpu);
static void rcu_preempt_process_callbacks(void); static void rcu_preempt_process_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp); static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake);
#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */ #endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
static int rcu_preempt_pending(int cpu); static int rcu_preempt_pending(int cpu);
static int rcu_preempt_needs_cpu(int cpu); static int rcu_preempt_needs_cpu(int cpu);

16
kernel/rcutree_plugin.h
View File

@ -410,7 +410,7 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
* then we need to report up the rcu_node hierarchy. * then we need to report up the rcu_node hierarchy.
*/ */
if (!empty_exp && empty_exp_now) if (!empty_exp && empty_exp_now)
rcu_report_exp_rnp(&rcu_preempt_state, rnp); rcu_report_exp_rnp(&rcu_preempt_state, rnp, true);
} else { } else {
local_irq_restore(flags); local_irq_restore(flags);
} }
@ -732,9 +732,13 @@ static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
* recursively up the tree. (Calm down, calm down, we do the recursion * recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!) * 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. * Caller must hold sync_rcu_preempt_exp_mutex.
*/ */
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake)
{ {
unsigned long flags; unsigned long flags;
unsigned long mask; unsigned long mask;
@ -747,7 +751,8 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
} }
if (rnp->parent == NULL) { if (rnp->parent == NULL) {
raw_spin_unlock_irqrestore(&rnp->lock, flags); raw_spin_unlock_irqrestore(&rnp->lock, flags);
wake_up(&sync_rcu_preempt_exp_wq); if (wake)
wake_up(&sync_rcu_preempt_exp_wq);
break; break;
} }
mask = rnp->grpmask; mask = rnp->grpmask;
@ -780,7 +785,7 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
must_wait = 1; must_wait = 1;
} }
if (!must_wait) if (!must_wait)
rcu_report_exp_rnp(rsp, rnp); rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */
} }
/* /*
@ -1072,7 +1077,8 @@ EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
* report on tasks preempted in RCU read-side critical sections during * report on tasks preempted in RCU read-side critical sections during
* expedited RCU grace periods. * expedited RCU grace periods.
*/ */
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake)
{ {
return; return;
} }