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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-07-01 11:26:57 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-07 16:27:20 -0700
commitbde6c3aa993066acb0d6ce32ecabe03b9d5df92d (patch)
tree09ec78a9cfa751ce36288c32c4e5112f34af8582 /kernel/rcu
parent8315f42295d2667a7f942f154b73a86fd7cb2227 (diff)
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rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops
RCU-tasks requires the occasional voluntary context switch from CPU-bound in-kernel tasks. In some cases, this requires instrumenting cond_resched(). However, there is some reluctance to countenance unconditionally instrumenting cond_resched() (see http://lwn.net/Articles/603252/), so this commit creates a separate cond_resched_rcu_qs() that may be used in place of cond_resched() in locations prone to long-duration in-kernel looping. This commit currently instruments only RCU-tasks. Future possibilities include also instrumenting RCU, RCU-bh, and RCU-sched in order to reduce IPI usage. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/rcutorture.c4
-rw-r--r--kernel/rcu/tree.c12
-rw-r--r--kernel/rcu/tree_plugin.h2
3 files changed, 9 insertions, 9 deletions
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 948a7693748e..178716713e11 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -667,7 +667,7 @@ static int rcu_torture_boost(void *arg)
}
call_rcu_time = jiffies;
}
- cond_resched();
+ cond_resched_rcu_qs();
stutter_wait("rcu_torture_boost");
if (torture_must_stop())
goto checkwait;
@@ -1019,7 +1019,7 @@ rcu_torture_reader(void *arg)
__this_cpu_inc(rcu_torture_batch[completed]);
preempt_enable();
cur_ops->readunlock(idx);
- cond_resched();
+ cond_resched_rcu_qs();
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
if (irqreader && cur_ops->irq_capable) {
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8ad91d1e317d..e23dad0661e2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1647,7 +1647,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
rnp->level, rnp->grplo,
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
- cond_resched();
+ cond_resched_rcu_qs();
}
mutex_unlock(&rsp->onoff_mutex);
@@ -1736,7 +1736,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
/* smp_mb() provided by prior unlock-lock pair. */
nocb += rcu_future_gp_cleanup(rsp, rnp);
raw_spin_unlock_irq(&rnp->lock);
- cond_resched();
+ cond_resched_rcu_qs();
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq(&rnp->lock);
@@ -1785,7 +1785,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
/* Locking provides needed memory barrier. */
if (rcu_gp_init(rsp))
break;
- cond_resched();
+ cond_resched_rcu_qs();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@@ -1828,10 +1828,10 @@ static int __noreturn rcu_gp_kthread(void *arg)
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
- cond_resched();
+ cond_resched_rcu_qs();
} else {
/* Deal with stray signal. */
- cond_resched();
+ cond_resched_rcu_qs();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@@ -2434,7 +2434,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
struct rcu_node *rnp;
rcu_for_each_leaf_node(rsp, rnp) {
- cond_resched();
+ cond_resched_rcu_qs();
mask = 0;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index a7997e272564..7672586d3920 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1848,7 +1848,7 @@ static int rcu_oom_notify(struct notifier_block *self,
get_online_cpus();
for_each_online_cpu(cpu) {
smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
- cond_resched();
+ cond_resched_rcu_qs();
}
put_online_cpus();