Messages in this thread Patch in this message | | | Date | Thu, 23 Jan 2020 15:39:38 -0500 | From | Steven Rostedt <> | Subject | [PATCH RT 08/30] hrtimer: Use READ_ONCE to access timer->base in hrimer_grab_expiry_lock() |
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4.19.94-rt39-rc2 stable review patch. If anyone has any objections, please let me know.
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From: Julien Grall <julien.grall@arm.com>
[ Upstream commit 2c8fdbe7ef0ad06c1a326886c5954e117b5657d6 ]
The update to timer->base is protected by the base->cpu_base->lock(). However, hrtimer_grab_expirty_lock() does not access it with the lock.
So it would theorically be possible to have timer->base changed under our feet. We need to prevent the compiler to refetch timer->base so the check and the access is performed on the same base.
Other access of timer->base are either done with a lock or protected with READ_ONCE(). So use READ_ONCE() in hrtimer_grab_expirty_lock().
Signed-off-by: Julien Grall <julien.grall@arm.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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 94d97eae0a46..d6026c170c2d 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -941,7 +941,7 @@ EXPORT_SYMBOL_GPL(hrtimer_forward); void hrtimer_grab_expiry_lock(const struct hrtimer *timer) { - struct hrtimer_clock_base *base = timer->base; + struct hrtimer_clock_base *base = READ_ONCE(timer->base); if (base && base->cpu_base) { spin_lock(&base->cpu_base->softirq_expiry_lock); -- 2.24.1
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