[tip:core/urgent] mutex: Don't spin when the owner CPU is offline or other weird cases
in [Kernel]
|
Prev: USBIP (staging) driver's dependency on drivers/usb/core internal headers
Next: [ARM] .gitignore: Ignore piggy.lzo, lib1funcs.S and vmlinux
From: tip-bot for Benjamin Herrenschmidt on 23 Apr 2010 07:00 Commit-ID: 4b402210486c6414fe5fbfd85934a0a22da56b04 Gitweb: http://git.kernel.org/tip/4b402210486c6414fe5fbfd85934a0a22da56b04 Author: Benjamin Herrenschmidt <benh(a)kernel.crashing.org> AuthorDate: Fri, 16 Apr 2010 23:20:00 +0200 Committer: Ingo Molnar <mingo(a)elte.hu> CommitDate: Fri, 23 Apr 2010 11:00:28 +0200 mutex: Don't spin when the owner CPU is offline or other weird cases 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(a)kernel.crashing.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl> LKML-Reference: <1271212509.13059.135.camel(a)pasglop> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- kernel/sched.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 6af210a..de0bd26 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3780,7 +3780,7 @@ 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 @@ -3790,14 +3790,14 @@ 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); @@ -3816,7 +3816,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner) cpu_relax(); } -out: + return 1; } #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |