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 <[email protected]> --- 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) { -- 2.17.1
