Commit-ID: 444da518fd554eb1b9875dc97fac6ec249cee330
Gitweb: https://git.kernel.org/tip/444da518fd554eb1b9875dc97fac6ec249cee330
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 4 Jul 2018 14:14:42 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Wed, 29 Aug 2018 09:20:48 -0700
rcutorture: Force occasional reader waits
Deferred quiescent states can interact with the scheduler, but
rcu_torture_reader() does not force such interaction all that frequently.
This commit therefore blocks for one jiffy after ten jiffies of read-side
runtime. This has the beneficial effect of being most likely to block
just after long-running readers, and it is exactly these readers that
are most likely to have been preempted (in CONFIG_PREEMPT=y kernels).
This in turn helps increase the probability that a deferred quiescent
state will be seen by RCU's context-switch hooks.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/rcutorture.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index c596c6f1e457..50a4f0ed4ebf 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1387,6 +1387,7 @@ static void rcu_torture_timer(struct timer_list *unused)
static int
rcu_torture_reader(void *arg)
{
+ unsigned long lastsleep = jiffies;
DEFINE_TORTURE_RANDOM(rand);
struct timer_list t;
@@ -1402,6 +1403,10 @@ rcu_torture_reader(void *arg)
}
if (!rcu_torture_one_read(&rand))
schedule_timeout_interruptible(HZ);
+ if (time_after(jiffies, lastsleep)) {
+ schedule_timeout_interruptible(1);
+ lastsleep = jiffies + 10;
+ }
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
if (irqreader && cur_ops->irq_capable) {
|