The following commit has been merged into the timers/urgent branch of tip: Commit-ID: 6881e75237a84093d0986f56223db3724619f26e Gitweb: https://git.kernel.org/tip/6881e75237a84093d0986f56223db3724619f26e Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Wed, 31 Jul 2024 12:23:51 +02:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Wed, 31 Jul 2024 12:37:43 +02:00 tick/broadcast: Move per CPU pointer access into the atomic section The recent fix for making the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed as compilers hoist the access into the non-preemptible region where the pointer is actually used. But of course it's valid that the compiler keeps it at the place where the code puts it which rightfully triggers: BUG: using smp_processor_id() in preemptible [00000000] code: caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0 Move it to the actual usage site which is in a non-preemptible region. Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable") Reported-by: David Wang <00107082@xxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Yu Liao <liaoyu15@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx --- kernel/time/tick-broadcast.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index b484309..ed58eeb 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -1141,7 +1141,6 @@ void tick_broadcast_switch_to_oneshot(void) #ifdef CONFIG_HOTPLUG_CPU void hotplug_cpu__broadcast_tick_pull(int deadcpu) { - struct tick_device *td = this_cpu_ptr(&tick_cpu_device); struct clock_event_device *bc; unsigned long flags; @@ -1167,6 +1166,8 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu) * device to avoid the starvation. */ if (tick_check_broadcast_expired()) { + struct tick_device *td = this_cpu_ptr(&tick_cpu_device); + cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask); tick_program_event(td->evtdev->next_event, 1); }
