Commit 444da518 authored Jul 04, 2018 by Paul E. McKenney

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@linux.vnet.ibm.com>

parent 31e74907

kernel/rcu/rcutorture.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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) {

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