From: Julien Grall Date: Wed, 21 Aug 2019 10:24:09 +0100 Subject: [PATCH 294/351] hrtimer: Prevent using hrtimer_grab_expiry_lock() on migration_base Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=3ef8d3a148a827f4f173179ea176d6deae3a4517 [ Upstream commit cef1b87f98823af923a386f3f69149acb212d4a1 ] As tglx puts it: |If base == migration_base then there is no point to lock soft_expiry_lock |simply because the timer is not executing the callback in soft irq context |and the whole lock/unlock dance can be avoided. Furthermore, all the path leading to hrtimer_grab_expiry_lock() assumes timer->base and timer->base->cpu_base are always non-NULL. So it is safe to remove the NULL checks here. Signed-off-by: Julien Grall Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908211557420.2223@nanos.tec.linutronix.de Signed-off-by: Steven Rostedt (VMware) [bigeasy: rewrite changelog] Signed-off-by: Sebastian Andrzej Siewior --- kernel/time/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 24bfae0e92e2..3f9d156c36f1 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -961,7 +961,7 @@ void hrtimer_grab_expiry_lock(const struct hrtimer *timer) { struct hrtimer_clock_base *base = READ_ONCE(timer->base); - if (timer->is_soft && base && base->cpu_base) { + if (timer->is_soft && base != &migration_base) { spin_lock(&base->cpu_base->softirq_expiry_lock); spin_unlock(&base->cpu_base->softirq_expiry_lock); }