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hrtimer: Protect lockless access to timer->base 

The update to timer->base is protected by the base->cpu_base->lock().
However, hrtimer_cancel_wait_running() does access it lockless.  So the
compiler is allowed to refetch timer->base which can cause havoc when the
timer base is changed concurrently.

Use READ_ONCE() to prevent this.

[ tglx: Adapted from a RT patch ]

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190821092409.13225-2-julien.grall@arm.com
This commit is contained in:
Julien Grall 2019-08-21 10:24:07 +01:00 committed by Thomas Gleixner
parent 7cb9a94c15
commit dd2261ed45
1 changed files with 2 additions and 1 deletions
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3
kernel/time/hrtimer.c
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@ -1214,7 +1214,8 @@ static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
*/ */
void hrtimer_cancel_wait_running(const struct hrtimer *timer) void hrtimer_cancel_wait_running(const struct hrtimer *timer)
{ {
struct hrtimer_clock_base *base = timer->base; /* Lockless read. Prevent the compiler from reloading it below */
struct hrtimer_clock_base *base = READ_ONCE(timer->base);
if (!timer->is_soft || !base || !base->cpu_base) { if (!timer->is_soft || !base || !base->cpu_base) {
cpu_relax(); cpu_relax();