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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-04-16 23:20:00 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-13 13:20:14 -0700
commitf40bf5f2fcef9e3123faf09cb33a5b0066e55b2d (patch)
parent19eb722b762e235458d912fa6621590fa9bd49ed (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>
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;
cpu = owner->cpu;
@@ -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)
return 1;