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Date: Mon, 28 Apr 2008 09:52:53 +0200 From: Heiko Carstens <heiko.carstens@...ibm.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Gautham R Shenoy <ego@...ibm.com>, Ingo Molnar <mingo@...e.hu>, Paul Jackson <pj@....com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] sched: missing locking in sched_domains code On Mon, Apr 28, 2008 at 12:28:53AM -0700, Andrew Morton wrote: > On Mon, 28 Apr 2008 09:09:46 +0200 Heiko Carstens <heiko.carstens@...ibm.com> wrote: > > > On Sun, Apr 27, 2008 at 06:39:26PM -0700, Andrew Morton wrote: > > > On Sun, 27 Apr 2008 23:12:24 +0200 Heiko Carstens <heiko.carstens@...ibm.com> wrote: > > > > Index: linux-2.6/kernel/cpuset.c > > > > =================================================================== > > > > --- linux-2.6.orig/kernel/cpuset.c > > > > +++ linux-2.6/kernel/cpuset.c > > > > @@ -684,7 +684,9 @@ restart: > > > > rebuild: > > > > /* Have scheduler rebuild sched domains */ > > > > get_online_cpus(); > > > > + mutex_lock(&sched_domains_mutex); > > > > partition_sched_domains(ndoms, doms, dattr); > > > > + mutex_unlock(&sched_domains_mutex); > > > > put_online_cpus(); > > > > > > > > > > It seems a bit fragile to take this lock in the caller without even adding > > > a comment at the callee site which documents the new locking rule. > > > > > > It would be more robust to take the lock within partition_sched_domains(). > > > > > > partition_sched_domains() already covers itself with lock_doms_cur(). Can > > > we take that in arch_reinit_sched_domains() rather than adding the new lock? > > > > I think you meant taking it in partition_sched_domains? > > What I meant was: rather than adding the new sched_domains_mutex, can we > instead call lock_doms_cur() from arch_reinit_sched_domains() and > sched_init_smp()? Borrow the existing lock? > > Whether that makes sense depends upon what lock_doms_cur() semantically > *means*. As that appears to be somewhat of a secret, we get to decide ;) Oh, I didn't realize that lock_doms_cur() was only used in one function. So that should work. Will try. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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