This is a note to let you know that I've just added the patch titled
torture: Fix hang during kthread shutdown phase
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
torture-fix-hang-during-kthread-shutdown-phase.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d52d3a2bf408ff86f3a79560b5cce80efb340239 Mon Sep 17 00:00:00 2001
From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
Date: Sun, 1 Jan 2023 06:15:55 +0000
Subject: torture: Fix hang during kthread shutdown phase
From: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
commit d52d3a2bf408ff86f3a79560b5cce80efb340239 upstream.
During rcutorture shutdown, the rcu_torture_cleanup() function calls
torture_cleanup_begin(), which sets the fullstop global variable to
FULLSTOP_RMMOD. This causes the rcutorture threads for readers and
fakewriters to exit all of their "while" loops and start shutting down.
They then call torture_kthread_stopping(), which in turn waits for
kthread_stop() to be called. However, rcu_torture_cleanup() has
not yet called kthread_stop() on those threads, and before it gets a
chance to do so, multiple instances of torture_kthread_stopping() invoke
schedule_timeout_interruptible(1) in a tight loop. Tracing confirms that
TIMER_SOFTIRQ can then continuously execute timer callbacks. If that
TIMER_SOFTIRQ preempts the task executing rcu_torture_cleanup(), that
task might never invoke kthread_stop().
This commit improves this situation by increasing the timeout passed to
schedule_timeout_interruptible() from one jiffy to 1/20th of a second.
This change prevents TIMER_SOFTIRQ from monopolizing its CPU, thus
allowing rcu_torture_cleanup() to carry out the needed kthread_stop()
invocations. Testing has shown 100 runs of TREE07 passing reliably,
as oppose to the tens-of-percent failure rates seen beforehand.
Cc: Paul McKenney <paulmck@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 6.0.x
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/torture.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -788,7 +788,7 @@ void torture_kthread_stopping(char *titl
VERBOSE_TOROUT_STRING(buf);
while (!kthread_should_stop()) {
torture_shutdown_absorb(title);
- schedule_timeout_uninterruptible(1);
+ schedule_timeout_uninterruptible(HZ / 20);
}
}
EXPORT_SYMBOL_GPL(torture_kthread_stopping);
Patches currently in stable-queue which might be from joel@xxxxxxxxxxxxxxxxx are
queue-5.10/timers-nohz-switch-to-oneshot_stopped-in-the-low-res-handler-when-the-tick-is-stopped.patch
queue-5.10/tick-detect-and-fix-jiffies-update-stall.patch
queue-5.10/torture-fix-hang-during-kthread-shutdown-phase.patch
