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authorIngo Molnar <mingo@kernel.org>2016-10-04 09:55:57 +0200
committerIngo Molnar <mingo@kernel.org>2016-10-04 09:55:57 +0200
commitbe6a2e4c46cc122ba9113ba569fbc50fad075fff (patch)
treeee35fb58cc7d610b22cb2792eef18b5a813f018c /kernel/smpboot.c
parent597f03f9d133e9837d00965016170271d4f87dcf (diff)
downloadlwn-be6a2e4c46cc122ba9113ba569fbc50fad075fff.tar.gz
lwn-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.c2
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;