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From: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Date: Tue, 28 Apr 2020 16:40:26 +0200
Subject: [PATCH 324/342] hrtimer: fix logic for when grabbing
softirq_expiry_lock can be elided
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=44b8364a13277bc84e81f619bd8db3c98cd5f63d
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 <rasmus.villemoes@prevas.dk>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
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 0f841f18c363..a84673149881 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -971,7 +971,7 @@ 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)) {
spin_lock(&base->cpu_base->softirq_expiry_lock);
spin_unlock(&base->cpu_base->softirq_expiry_lock);
}
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