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tick/broadcast: Move per CPU pointer access into the atomic section

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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: f7d43dd206 ("tick/broadcast: Make takeover of broadcast hrtimer reliable")
Reported-by: David Wang <00107082@163.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yu Liao <liaoyu15@huawei.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx
This commit is contained in:
Thomas Gleixner 2024-07-31 12:23:51 +02:00
parent 8400291e28
commit 6881e75237
1 changed files with 2 additions and 1 deletions
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3
kernel/time/tick-broadcast.c
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@ -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);
}