> > I've queued the below patch Thanks. Should it make -stable as well ?
Cheers, Ben. > --- > Subject: mutex: Don't spin when the owner CPU is offline or other weird cases > From: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Date: Fri Apr 16 23:20:00 CEST 2010 > > 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 <b...@kernel.crashing.org> > Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl> > LKML-Reference: <1271212509.13059.135.ca...@pasglop> > --- > kernel/sched.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > Index: linux-2.6/kernel/sched.c > =================================================================== > --- linux-2.6.orig/kernel/sched.c > +++ linux-2.6/kernel/sched.c > @@ -3647,7 +3647,7 @@ int mutex_spin_on_owner(struct mutex *lo > * the mutex owner just released it and exited. > */ > if (probe_kernel_address(&owner->cpu, cpu)) > - goto out; > + return 0; > #else > cpu = owner->cpu; > #endif > @@ -3657,14 +3657,14 @@ int mutex_spin_on_owner(struct mutex *lo > * 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); > > @@ -3683,7 +3683,7 @@ int mutex_spin_on_owner(struct mutex *lo > > cpu_relax(); > } > -out: > + > return 1; > } > #endif > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
