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| author | Ingo Molnar <mingo@kernel.org> | 2016-10-04 09:55:57 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-10-04 09:55:57 +0200 |
| commit | be6a2e4c46cc122ba9113ba569fbc50fad075fff (patch) | |
| tree | ee35fb58cc7d610b22cb2792eef18b5a813f018c /kernel/smpboot.c | |
| parent | 597f03f9d133e9837d00965016170271d4f87dcf (diff) | |
| download | linux-stable-be6a2e4c46cc122ba9113ba569fbc50fad075fff.tar.gz linux-stable-be6a2e4c46cc122ba9113ba569fbc50fad075fff.tar.bz2 linux-stable-be6a2e4c46cc122ba9113ba569fbc50fad075fff.zip | |
Revert "sched/core: Do not use smp_processor_id() with preempt enabled in smpboot_thread_fn()"
This reverts commit 4fa5cd5245b627db88c9ca08ae442373b02596b4.
The original change widens a preempt-off section, to avoid a seemingly unsafe
smp_processor_id() use.
During review I overlooked two facts:
- The code to calls a non-trivial function callback:
ht->park(td->cpu);
... which might (and does occasionally) sleep, triggering the warning.
- More importantly, as pointed out by Peter Zijlstra, using
smp_processor_id() in that context is safe, if it's done from
a kernel thread that is pinned to a single CPU - which is the
case here.
So revert to the original code that enables preemption sooner.
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: Alfred Chen <cchalpha@gmail.com>
Link: http://lkml.kernel.org/r/20160930015102.GB20189@yexl-desktop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/smpboot.c')
| -rw-r--r-- | kernel/smpboot.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/smpboot.c b/kernel/smpboot.c index fc0d8270f69e..13bc43d1fb22 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -122,12 +122,12 @@ static int smpboot_thread_fn(void *data) if (kthread_should_park()) { __set_current_state(TASK_RUNNING); + preempt_enable(); if (ht->park && td->status == HP_THREAD_ACTIVE) { BUG_ON(td->cpu != smp_processor_id()); ht->park(td->cpu); td->status = HP_THREAD_PARKED; } - preempt_enable(); kthread_parkme(); /* We might have been woken for stop */ continue; |