From: "Paul E. McKenney" <paulmck@kernel.org>
To: Anna-Maria Behnsen <anna-maria@linutronix.de>,
Frederic Weisbecker <frederic@kernel.org>,
Thomas Gleixner <tglx@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
io-uring@vger.kernel.org, netdev@vger.kernel.org,
kernel-team@meta.com, "Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH 12/12] hrtimer: Apply READ_ONCE() to lockless base->running loads
Date: Fri, 18 Sep 2026 17:14:28 -0700 [thread overview]
Message-ID: <20260919001428.3133388-12-paulmck@kernel.org> (raw)
In-Reply-To: <5dca353c-6b3f-4d01-8808-bef2c0dd7af7@paulmck-laptop>
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 <paulmck@kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@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 91ac2b517637..b3b4776c17a1 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1997,7 +1997,7 @@ 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));
@@ -2034,7 +2034,7 @@ 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.
@@ -2093,7 +2093,7 @@ 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,
--
2.40.1
prev parent reply other threads:[~2026-09-19 0:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-19 0:13 [PATCH v2] Fix data races on hrtimer_sleeper ->task field Paul E. McKenney
2026-09-19 0:14 ` [PATCH 01/12] hrtimer: Mark data-racy accesses to " Paul E. McKenney
2026-09-19 0:14 ` [PATCH 02/12] aio: Use accessor for " Paul E. McKenney
2026-09-19 0:14 ` [PATCH 03/12] wait: " Paul E. McKenney
2026-09-19 0:14 ` [PATCH 04/12] io-uring/rw: " Paul E. McKenney
2026-09-19 0:14 ` [PATCH 05/12] futex: Use accessor for hrtimer_sleeper ->task field in waitwake.c Paul E. McKenney
2026-09-19 0:14 ` [PATCH 06/12] timers: Use accessor for hrtimer_sleeper ->task field in sleep_timeout.c Paul E. McKenney
2026-09-19 0:14 ` [PATCH 07/12] net: pktgen: Use accessor for hrtimer_sleeper ->task field Paul E. McKenney
2026-09-19 0:14 ` [PATCH 08/12] rtmutex: " Paul E. McKenney
2026-09-19 0:14 ` [PATCH 09/12] futex: Use accessor for hrtimer_sleeper ->task field in requeue Paul E. McKenney
2026-09-19 0:14 ` [PATCH 10/12] hrtimer: Update hrtimer_resolution only if value changes Paul E. McKenney
2026-09-19 0:14 ` [PATCH 11/12] hrtimer: Mark the hrtimer_sleeper structure's ->task field __private Paul E. McKenney
2026-09-19 0:14 ` Paul E. McKenney [this message]
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