From 5dffe33bfdafcc768d090c55479f515585509ffa Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 18 Sep 2026 17:14:28 -0700 Subject: [PATCH] hrtimer: Apply READ_ONCE() to lockless base->running loads Updates to base->running are protected by the hrtimer base lock, but some loads are lockless. Therefore, prevent compiler mischief by applying READ_ONCE() to the lockless loads. KCSAN located this issue. Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260919001428.3133388-12-paulmck@kernel.org --- kernel/time/hrtimer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 205406460993..17dd38a6cee7 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -2004,7 +2004,7 @@ bool hrtimer_active(const struct hrtimer *timer) base = READ_ONCE(timer->base); seq = raw_read_seqcount_begin(&base->seq); - if (timer->is_queued || base->running == timer) + if (timer->is_queued || READ_ONCE(base->running) == timer) return true; } while (read_seqcount_retry(&base->seq, seq) || base != READ_ONCE(timer->base)); @@ -2041,7 +2041,7 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, struct hrtimer_cloc lockdep_assert_held(&cpu_base->lock); debug_hrtimer_deactivate(timer); - base->running = timer; + WRITE_ONCE(base->running, timer); /* * Separate the ->running assignment from the ->is_queued assignment. @@ -2100,7 +2100,7 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, struct hrtimer_cloc raw_write_seqcount_barrier(&base->seq); WARN_ON_ONCE(base->running != timer); - base->running = NULL; + WRITE_ONCE(base->running, NULL); } static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,