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Two fixes for the timer/clocksource code:

Browse Source 
- 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 in testing as some compilers hoist the access into
       the non-preemotible section where the pointer is actually used, but
       obviously compilers can rightfully invoke it where the code put it.
 
       Move it into the non-preemptible section right to the actual usage
       side to cure it.
 
     - The clocksource watchdog is supposed to emit a warning when the retry
       count is greater than one and the number of retries reaches the
       limit. The condition is backwards and warns always when the count is
       greater than one. Fixup the condition to prevent spamming dmesg.
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Merge tag 'timers-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "Two fixes for the timer/clocksource code:

   - The recent fix to make the take over of the broadcast timer more
     reliable retrieves a per CPU pointer in preemptible context.

     This went unnoticed in testing as some compilers hoist the access
     into the non-preemotible section where the pointer is actually
     used, but obviously compilers can rightfully invoke it where the
     code put it.

     Move it into the non-preemptible section right to the actual usage
     side to cure it.

   - The clocksource watchdog is supposed to emit a warning when the
     retry count is greater than one and the number of retries reaches
     the limit.

     The condition is backwards and warns always when the count is
     greater than one. Fixup the condition to prevent spamming dmesg"

* tag 'timers-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource: Fix brown-bag boolean thinko in cs_watchdog_read()
  tick/broadcast: Move per CPU pointer access into the atomic section
This commit is contained in:
Linus Torvalds 2024-08-04 08:50:16 -07:00
commit 61ca6c7829
2 changed files with 3 additions and 2 deletions
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2
kernel/time/clocksource.c
View File

@ -246,7 +246,7 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow,
wd_delay = cycles_to_nsec_safe(watchdog, *wdnow, wd_end);
if (wd_delay <= WATCHDOG_MAX_SKEW) {
if (nretries > 1 || nretries >= max_retries) {
if (nretries > 1 && nretries >= max_retries) {
pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
smp_processor_id(), watchdog->name, nretries);
}

3
kernel/time/tick-broadcast.c
View File

@ -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);
}