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 10/12] hrtimer: Update hrtimer_resolution only if value changes
Date: Fri, 18 Sep 2026 17:14:26 -0700 [thread overview]
Message-ID: <20260919001428.3133388-10-paulmck@kernel.org> (raw)
In-Reply-To: <5dca353c-6b3f-4d01-8808-bef2c0dd7af7@paulmck-laptop>
Currently, the hrtimer_switch_to_hres() function unconditionally updates
hrtimer_resolution to HIGH_RES_NSEC. This causes KCSAN false positives
in kernels built with CONFIG_KCSAN_STRICT=y. It also causes unnecessary
cache-line traffic on the many code paths that load hrtimer_resolution,
which is especially regrettable because the value of hrtimer_resolution
normally changes only once during the lifetime of a given kernel.
Therefore, update the value of hrtimer_resolution to HIGH_RES_NSEC only
if it does not already have that value.
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 | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 53c57d585696..91ac2b517637 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -780,7 +780,8 @@ static void hrtimer_switch_to_hres(void)
return;
}
base->hres_active = true;
- hrtimer_resolution = HIGH_RES_NSEC;
+ if (hrtimer_resolution != HIGH_RES_NSEC)
+ hrtimer_resolution = HIGH_RES_NSEC;
tick_setup_sched_timer(true);
/* "Retrigger" the interrupt to get things going */
--
2.40.1
next 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 ` Paul E. McKenney [this message]
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 ` [PATCH 12/12] hrtimer: Apply READ_ONCE() to lockless base->running loads Paul E. McKenney
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