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Merge tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull timer fixes from Ingo Molnar:
 "Update/fix two CPU sanity checks in the hotplug and the boot code, and
  fix a typo in the Kconfig help text.

  [ Context: the first two commits are the result of an ongoing
    annotation+review work of (intentional) tick_do_timer_cpu() data
    races reported by KCSAN, but the annotations aren't fully cooked
    yet ]"

* tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"
  tick/sched: Remove bogus boot "safety" check
  tick: Remove pointless cpu valid check in hotplug code
This commit is contained in:
Linus Torvalds
2020-12-27 09:03:41 -08:00
parent 3b80dee70e f6f5cd840a
commit 2eeefc60ad
3 changed files with 4 additions and 15 deletions
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2
kernel/time/Kconfig
View File

@@ -141,7 +141,7 @@ config CONTEXT_TRACKING_FORCE
dynticks working. dynticks working.
This option stands for testing when an arch implements the This option stands for testing when an arch implements the
context tracking backend but doesn't yet fullfill all the context tracking backend but doesn't yet fulfill all the
requirements to make the full dynticks feature working. requirements to make the full dynticks feature working.
Without the full dynticks, there is no way to test the support Without the full dynticks, there is no way to test the support
for context tracking and the subsystems that rely on it: RCU for context tracking and the subsystems that rely on it: RCU

10
kernel/time/tick-common.c
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@@ -407,17 +407,13 @@ EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
/* /*
* Transfer the do_timer job away from a dying cpu. * Transfer the do_timer job away from a dying cpu.
* *
* Called with interrupts disabled. Not locking required. If * Called with interrupts disabled. No locking required. If
* tick_do_timer_cpu is owned by this cpu, nothing can change it. * tick_do_timer_cpu is owned by this cpu, nothing can change it.
*/ */
void tick_handover_do_timer(void) void tick_handover_do_timer(void)
{ {
if (tick_do_timer_cpu == smp_processor_id()) { if (tick_do_timer_cpu == smp_processor_id())
int cpu = cpumask_first(cpu_online_mask); tick_do_timer_cpu = cpumask_first(cpu_online_mask);
tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
TICK_DO_TIMER_NONE;
}
} }
/* /*

7
kernel/time/tick-sched.c
View File

@@ -989,13 +989,6 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
*/ */
if (tick_do_timer_cpu == cpu) if (tick_do_timer_cpu == cpu)
return false; return false;
/*
* Boot safety: make sure the timekeeping duty has been
* assigned before entering dyntick-idle mode,
* tick_do_timer_cpu is TICK_DO_TIMER_BOOT
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_BOOT))
return false;
/* Should not happen for nohz-full */ /* Should not happen for nohz-full */
if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))