[PATCH] timers: Check timer_pending() before reading bucket index

[PATCH] timers: Check timer_pending() before reading bucket index

[Liang Hao]

Only read the cached wheel index when the timer is still queued.
No functional change.

Signed-off-by: Liang Hao <haohlliang@gmail.com>
---
 kernel/time/timer.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index ae9abf14688e..9f3b199d3075 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -897,11 +897,13 @@ static inline void detach_timer(struct timer_list *timer, bool clear_pending)
 static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
 			     bool clear_pending)
 {
-	unsigned idx = timer_get_idx(timer);
+	unsigned int idx;
 
 	if (!timer_pending(timer))
 		return 0;
 
+	idx = timer_get_idx(timer);
+
 	if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
 		__clear_bit(idx, base->pending_map);
 		base->next_expiry_recalc = true;
-- 
2.50.1 (Apple Git-155)

Re: [PATCH] timers: Check timer_pending() before reading bucket index

[Thomas Gleixner]

On Fri, Aug 28 2026 at 22:53, Liang Hao wrote:

> Only read the cached wheel index when the timer is still queued.
> No functional change.

Which problem is actually solved by this?

Re: [PATCH] timers: Check timer_pending() before reading bucket index

[Liang Hao]

On Sat, Sep 05 2026 at 22:35, Thomas Gleixner wrote:
> Which problem is actually solved by this?

None that shows up as a bug. The index is never used when the
timer is not queued; I only reordered the checks. I'll drop it.

Thanks,
Liang Hao