redonkable/alistair23-linux
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rcu: Use rsp->expedited_wq instead of sync_rcu_preempt_exp_wq

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Now that there is an ->expedited_wq waitqueue in each rcu_state structure,
there is no need for the sync_rcu_preempt_exp_wq global variable.  This
commit therefore substitutes ->expedited_wq for sync_rcu_preempt_exp_wq.
It also initializes ->expedited_wq only once at boot instead of at the
start of each expedited grace period.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-07-29 17:28:11 -07:00
parent 19a5ecde08
commit f4ecea309d
2 changed files with 3 additions and 5 deletions
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2
kernel/rcu/tree.c
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@ -3556,7 +3556,6 @@ void synchronize_sched_expedited(void)
rcu_exp_gp_seq_start(rsp); rcu_exp_gp_seq_start(rsp);
/* Stop each CPU that is online, non-idle, and not us. */ /* Stop each CPU that is online, non-idle, and not us. */
init_waitqueue_head(&rsp->expedited_wq);
atomic_set(&rsp->expedited_need_qs, 1); /* Extra count avoids race. */ atomic_set(&rsp->expedited_need_qs, 1); /* Extra count avoids race. */
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
@ -4179,6 +4178,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
} }
init_waitqueue_head(&rsp->gp_wq); init_waitqueue_head(&rsp->gp_wq);
init_waitqueue_head(&rsp->expedited_wq);
rnp = rsp->level[rcu_num_lvls - 1]; rnp = rsp->level[rcu_num_lvls - 1];
for_each_possible_cpu(i) { for_each_possible_cpu(i) {
while (i > rnp->grphi) while (i > rnp->grphi)

6
kernel/rcu/tree_plugin.h
View file

@ -535,8 +535,6 @@ void synchronize_rcu(void)
} }
EXPORT_SYMBOL_GPL(synchronize_rcu); EXPORT_SYMBOL_GPL(synchronize_rcu);
static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
/* /*
* Return non-zero if there are any tasks in RCU read-side critical * Return non-zero if there are any tasks in RCU read-side critical
* sections blocking the current preemptible-RCU expedited grace period. * sections blocking the current preemptible-RCU expedited grace period.
@ -590,7 +588,7 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
raw_spin_unlock_irqrestore(&rnp->lock, flags); raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (wake) { if (wake) {
smp_mb(); /* EGP done before wake_up(). */ smp_mb(); /* EGP done before wake_up(). */
wake_up(&sync_rcu_preempt_exp_wq); wake_up(&rsp->expedited_wq);
} }
break; break;
} }
@ -729,7 +727,7 @@ void synchronize_rcu_expedited(void)
/* Wait for snapshotted ->blkd_tasks lists to drain. */ /* Wait for snapshotted ->blkd_tasks lists to drain. */
rnp = rcu_get_root(rsp); rnp = rcu_get_root(rsp);
wait_event(sync_rcu_preempt_exp_wq, wait_event(rsp->expedited_wq,
sync_rcu_preempt_exp_done(rnp)); sync_rcu_preempt_exp_done(rnp));
/* Clean up and exit. */ /* Clean up and exit. */