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authorJoel Fernandes (Google) <joel@joelfernandes.org>2023-01-01 06:15:55 +0000
committerPaul E. McKenney <paulmck@kernel.org>2023-01-05 12:10:35 -0800
commitd52d3a2bf408ff86f3a79560b5cce80efb340239 (patch)
tree43351d3edc66beb03f7ccb0f3dca91c2f0e86bb3 /kernel/torture.c
parent273661595c21f390d2522af06c7b552f907fe12a (diff)
torture: Fix hang during kthread shutdown phase
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@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Zhouyi Zhou <zhouzhouyi@gmail.com> Cc: <stable@vger.kernel.org> # 6.0.x Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/torture.c')
-rw-r--r--kernel/torture.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/torture.c b/kernel/torture.c
index 29afc62f2bfe..1a0519b836ac 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -915,7 +915,7 @@ void torture_kthread_stopping(char *title)
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);