On Tue, 28 Apr 2020 16:40:26 +0200 Rasmus Villemoes <[email protected]> wrote:
> Commit > > hrtimer: Add a missing bracket and hide `migration_base' on !SMP > > which is 47b6de0b7f22 in 5.2-rt and 40aae5708e7a in 4.19-rt, > inadvertently changed the logic from base != &migration_base to base > == &migration_base. > > On !CONFIG_SMP, the effect was to effectively always elide this > lock/unlock pair (since is_migration_base() is unconditionally false), > which for me consistently causes lockups during reboot, and reportedly > also often causes a hang during boot. > > Adding this logical negation (or, what is effectively the same thing > on !CONFIG_SMP, reverting the above commit as well as "hrtimer: > Prevent using hrtimer_grab_expiry_lock() on migration_base") fixes > that lockup. > > Fixes: 40aae5708e7a (hrtimer: Add a missing bracket and hide `migration_base' > on !SMP) # 4.19-rt > Fixes: 47b6de0b7f22 (hrtimer: Add a missing bracket and hide `migration_base' > on !SMP) # 5.2-rt > Signed-off-by: Rasmus Villemoes <[email protected]> > --- > Something like this? I wasn't sure what Fixes: tag(s) to include, if > any. It's quite possible the same fix is needed on earlier -rt > kernels, I didn't check. > > 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 e54a95de8b79..c3966c090246 100644 > --- a/kernel/time/hrtimer.c > +++ b/kernel/time/hrtimer.c > @@ -953,7 +953,7 @@ void hrtimer_grab_expiry_lock(const struct hrtimer *timer) > { > struct hrtimer_clock_base *base = READ_ONCE(timer->base); > > - if (timer->is_soft && is_migration_base(base)) { > + if (timer->is_soft && !is_migration_base(base)) { That was my sloppiness in not seeing that 5.2-rt had == and 4.19 had !=. Thanks for tracking this down! Reviewed-by: Steven Rostedt (VMware) <[email protected]> -- Steve > spin_lock(&base->cpu_base->softirq_expiry_lock); > spin_unlock(&base->cpu_base->softirq_expiry_lock); > }
