diff options
| author |   Eric Dumazet <edumazet@google.com> | 2019-10-08 10:32:04 -0700 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2019-10-14 15:51:49 +0200 |
| commit | ff229eee3d897f52bd001c841f2d3cce8853ecdc (patch) | |
| tree | ff2aeaf672e1e411d2054ca722f7d0e84eec72f6 /kernel/time/hrtimer.c | |
| parent | Linux 5.4-rc3 (diff) | |
| download | linux-dev-ff229eee3d897f52bd001c841f2d3cce8853ecdc.tar.xz linux-dev-ff229eee3d897f52bd001c841f2d3cce8853ecdc.zip | |
hrtimer: Annotate lockless access to timer->base
Followup to commit dd2261ed45aa ("hrtimer: Protect lockless access
to timer->base")
lock_hrtimer_base() fetches timer->base without lock exclusion.
Compiler is allowed to read timer->base twice (even if considered dumb)
which could end up trying to lock migration_base and return
&migration_base.
base = timer->base;
if (likely(base != &migration_base)) {
/* compiler reads timer->base again, and now (base == &migration_base)
raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
if (likely(base == timer->base))
return base; /* == &migration_base ! */
Similarly the write sides must use WRITE_ONCE() to avoid store tearing.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191008173204.180879-1-edumazet@google.com
Diffstat (limited to 'kernel/time/hrtimer.c')
| -rw-r--r-- | kernel/time/hrtimer.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 0d4dc241c0fb..65605530ee34 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -164,7 +164,7 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer, struct hrtimer_clock_base *base; for (;;) { - base = timer->base; + base = READ_ONCE(timer->base); if (likely(base != &migration_base)) { raw_spin_lock_irqsave(&base->cpu_base->lock, *flags); if (likely(base == timer->base)) @@ -244,7 +244,7 @@ again: return base; /* See the comment in lock_hrtimer_base() */ - timer->base = &migration_base; + WRITE_ONCE(timer->base, &migration_base); raw_spin_unlock(&base->cpu_base->lock); raw_spin_lock(&new_base->cpu_base->lock); @@ -253,10 +253,10 @@ again: raw_spin_unlock(&new_base->cpu_base->lock); raw_spin_lock(&base->cpu_base->lock); new_cpu_base = this_cpu_base; - timer->base = base; + WRITE_ONCE(timer->base, base); goto again; } - timer->base = new_base; + WRITE_ONCE(timer->base, new_base); } else { if (new_cpu_base != this_cpu_base && hrtimer_check_target(timer, new_base)) { |