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rcu: Use funnel locking for synchronize_rcu_expedited()'s polling loop

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This commit gets rid of synchronize_rcu_expedited()'s mutex_trylock()
polling loop in favor of the funnel-locking scheme that was abstracted
from synchronize_sched_expedited().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2015-06-25 19:03:16 -07:00
rodzic 7fd0ddc5bf
commit 29fd930940
2 zmienionych plików z 18 dodań i 33 usunięć
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15
kernel/rcu/tree.c
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@@ -3309,9 +3309,9 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
return rcu_seq_done(&rsp->expedited_sequence, s);
}
/* Common code for synchronize_sched_expedited() work-done checking. */
static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
atomic_long_t *stat, unsigned long s)
/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
atomic_long_t *stat, unsigned long s)
{
if (rcu_exp_gp_seq_done(rsp, s)) {
if (rnp)
@@ -3319,7 +3319,6 @@ static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
/* Ensure test happens before caller kfree(). */
smp_mb__before_atomic(); /* ^^^ */
atomic_long_inc(stat);
put_online_cpus();
return true;
}
return false;
@@ -3345,14 +3344,14 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
*/
rnp0 = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
for (; rnp0 != NULL; rnp0 = rnp0->parent) {
if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone1, s))
if (sync_exp_work_done(rsp, rnp1, &rsp->expedited_workdone1, s))
return NULL;
mutex_lock(&rnp0->exp_funnel_mutex);
if (rnp1)
mutex_unlock(&rnp1->exp_funnel_mutex);
rnp1 = rnp0;
}
if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone2, s))
if (sync_exp_work_done(rsp, rnp1, &rsp->expedited_workdone2, s))
return NULL;
return rnp1;
}
@@ -3402,8 +3401,10 @@ void synchronize_sched_expedited(void)
WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
rnp = exp_funnel_lock(rsp, s);
if (rnp == NULL)
if (rnp == NULL) {
put_online_cpus();
return; /* Someone else did our work for us. */
}
rcu_exp_gp_seq_start(rsp);