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SubjectRe: [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned
On Fri, Mar 12, 2021 at 12:36:41PM +0100, Frederic Weisbecker wrote:
> On Wed, Mar 03, 2021 at 04:00:15PM -0800, paulmck@kernel.org wrote:
> > From: "Paul E. McKenney" <paulmck@kernel.org>
> >
> > If there is heavy softirq activity, the softirq system will attempt
> > to awaken ksoftirqd and will stop the traditional back-of-interrupt
> > softirq processing. This is all well and good, but only if the
> > ksoftirqd kthreads already exist, which is not the case during early
> > boot, in which case the system hangs.
> >
> > One reproducer is as follows:
> >
> > tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_NO_HZ_IDLE=y CONFIG_HZ_PERIODIC=n" --bootargs "threadirqs=1" --trust-make
> >
> > This commit therefore adds a couple of existence checks for ksoftirqd
> > and forces back-of-interrupt softirq processing when ksoftirqd does not
> > yet exist. With this change, the above test passes.
> >
> > Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> > Reported-by: Uladzislau Rezki <urezki@gmail.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > [ paulmck: Remove unneeded check per Sebastian Siewior feedback. ]
> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
>
> Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

Applied, thank you!

Thanx, Paul

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