diff options
| author | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2010-04-16 23:20:00 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-08-13 13:20:14 -0700 |
| commit | f40bf5f2fcef9e3123faf09cb33a5b0066e55b2d (patch) | |
| tree | f822dd809cf81a4d5787e7e74907adbd97bca766 | |
| parent | 19eb722b762e235458d912fa6621590fa9bd49ed (diff) | |
mutex: Don't spin when the owner CPU is offline or other weird cases
commit 4b402210486c6414fe5fbfd85934a0a22da56b04 upstream.
Due to recent load-balancer changes that delay the task migration to
the next wakeup, the adaptive mutex spinning ends up in a live lock
when the owner's CPU gets offlined because the cpu_online() check
lives before the owner running check.
This patch changes mutex_spin_on_owner() to return 0 (don't spin) in
any case where we aren't sure about the owner struct validity or CPU
number, and if the said CPU is offline. There is no point going back &
re-evaluate spinning in corner cases like that, let's just go to
sleep.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1271212509.13059.135.camel@pasglop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/sched.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index e8aa03646899..9990074169fa 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5590,7 +5590,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner) * the mutex owner just released it and exited. */ if (probe_kernel_address(&owner->cpu, cpu)) - goto out; + return 0; #else cpu = owner->cpu; #endif @@ -5600,14 +5600,14 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner) * the cpu field may no longer be valid. */ if (cpu >= nr_cpumask_bits) - goto out; + return 0; /* * We need to validate that we can do a * get_cpu() and that we have the percpu area. */ if (!cpu_online(cpu)) - goto out; + return 0; rq = cpu_rq(cpu); @@ -5626,7 +5626,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner) cpu_relax(); } -out: + return 1; } #endif |