Commit 66bcb132 authored by Joel Fernandes (Google)'s avatar Joel Fernandes (Google) Committed by Frederic Weisbecker
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rcutorture: Replace schedule_timeout*() 1-jiffy waits with HZ/20 



In the past, spinning on schedule_timeout* with a wait of 1 jiffy has
hung the kernel. See for example d52d3a2b ("torture: Fix hang during
kthread shutdown phase").

This issue recently recurred in torture's stutter code.  The result is
that the function instantly returns and never goes to sleep, preempting
whatever might otherwise make useful forward progress.

To prevent future issues, apply the commit-d52d3a2b fix throughout
rcutorture, moving from a 1-jiffy wait to a 50-millisecond wait.

Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
parent 30639bfd

kernel/rcu/rcutorture.c

+6 −6
Original line number Diff line number Diff line
@@ -1149,7 +1149,7 @@ static int rcu_torture_boost(void *arg) 
				mutex_unlock(&boost_mutex);

				break;

			}

			schedule_timeout_uninterruptible(1);

			schedule_timeout_uninterruptible(HZ / 20);

		}



		/* Go do the stutter. */
@@ -1160,7 +1160,7 @@ checkwait: if (stutter_wait("rcu_torture_boost")) 
	/* Clean up and exit. */

	while (!kthread_should_stop()) {

		torture_shutdown_absorb("rcu_torture_boost");

		schedule_timeout_uninterruptible(1);

		schedule_timeout_uninterruptible(HZ / 20);

	}

	torture_kthread_stopping("rcu_torture_boost");

	return 0;
@@ -1183,7 +1183,7 @@ rcu_torture_fqs(void *arg) 
		fqs_resume_time = jiffies + fqs_stutter * HZ;

		while (time_before(jiffies, fqs_resume_time) &&

		       !kthread_should_stop()) {

			schedule_timeout_interruptible(1);

			schedule_timeout_interruptible(HZ / 20);

		}

		fqs_burst_remaining = fqs_duration;

		while (fqs_burst_remaining > 0 &&
@@ -2899,7 +2899,7 @@ static int rcu_torture_fwd_prog(void *args) 
			WRITE_ONCE(rcu_fwd_seq, rcu_fwd_seq + 1);

		} else {

			while (READ_ONCE(rcu_fwd_seq) == oldseq && !torture_must_stop())

				schedule_timeout_interruptible(1);

				schedule_timeout_interruptible(HZ / 20);

			oldseq = READ_ONCE(rcu_fwd_seq);

		}

		pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
@@ -3200,7 +3200,7 @@ static int rcu_torture_read_exit_child(void *trsp_in) 
	set_user_nice(current, MAX_NICE);

	// Minimize time between reading and exiting.

	while (!kthread_should_stop())

		schedule_timeout_uninterruptible(1);

		schedule_timeout_uninterruptible(HZ / 20);

	(void)rcu_torture_one_read(trsp, -1);

	return 0;

}
@@ -3248,7 +3248,7 @@ static int rcu_torture_read_exit(void *unused) 
	smp_mb(); // Store before wakeup.

	wake_up(&read_exit_wq);

	while (!torture_must_stop())

		schedule_timeout_uninterruptible(1);

		schedule_timeout_uninterruptible(HZ / 20);

	torture_kthread_stopping("rcu_torture_read_exit");

	return 0;

}