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rcutorture: Force occasional reader waits

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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>
This commit is contained in:
Paul E. McKenney 2018-07-04 14:14:42 -07:00
parent 31e7490741
commit 444da518fd
1 changed files with 5 additions and 0 deletions
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5
kernel/rcu/rcutorture.c
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@ -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) {