On Sun, Jan 1, 2023 at 1:16 AM Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> wrote: > > During shutdown of rcutorture, the shutdown thread in > rcu_torture_cleanup() calls torture_cleanup_begin() which sets fullstop > to FULLSTOP_RMMOD. This is enough to cause the rcutorture threads for > readers and fakewriters to breakout of their main while loop and start > shutting down. > > Once out of their main loop, they then call torture_kthread_stopping() > which in turn waits for kthread_stop() to be called, however > rcu_torture_cleanup() has not even called kthread_stop() on those > threads yet, it does that a bit later. However, before it gets a chance > to do so, torture_kthread_stopping() calls > schedule_timeout_interruptible(1) in a tight loop. Tracing confirmed > this makes the timer softirq constantly execute timer callbacks, while > never returning back to the softirq exit path and is essentially "locked > up" because of that. If the softirq preempts the shutdown thread, > kthread_stop() may never be called. > > This commit improves the situation dramatically, by increasing timeout > passed to schedule_timeout_interruptible() 1/20th of a second. This > causes the timer softirq to not lock up a CPU and everything works fine. > Testing has shown 100 runs of TREE07 passing reliably, which was not the > case before because of RCU stalls. > > Cc: Paul McKenney <paulmck@xxxxxxxxxx> > Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> > Cc: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # 6.0.x Question for stable maintainers: This patch is for mainline and 6.0 stable. However, it should also go to 6.1 stable. How do we tag it to do that? I did not know how to tag 2 stable versions. I guess the above implies > 6.0 ? Thanks, - Joel
