Messages in this thread Patch in this message | | | Date | Mon, 28 Apr 2008 11:17:45 +0200 | From | Heiko Carstens <> | Subject | Re: [PATCH] sched: missing locking in sched_domains code |
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On Mon, Apr 28, 2008 at 01:57:23AM -0700, Andrew Morton wrote: > On Mon, 28 Apr 2008 10:49:04 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > > /* doms_cur_mutex serializes access to doms_cur[] array */ > > -static DEFINE_MUTEX(doms_cur_mutex); > > +static DEFINE_MUTEX(sched_domains_mutex); > > The comment refers to a no-longer-existing lock, and no longer correctly > describes the lock's usage.
version 42. Please feel free to change the comment if you think it could be better :)
Subject: [PATCH] sched: fix locking in arch_reinit_sched_domains
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Concurrent calls to detach_destroy_domains and arch_init_sched_domains were prevented by the old scheduler subsystem cpu hotplug mutex. When this got converted to get_online_cpus() the locking got broken. Unlike before now several processes can concurrently enter the critical sections that were protected by the old lock.
So use the already present doms_cur_mutex to protect these sections again.
Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Jackson <pj@sgi.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> --- kernel/sched.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-)
Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -308,8 +308,10 @@ static DEFINE_PER_CPU(struct rt_rq, init */ static DEFINE_SPINLOCK(task_group_lock); -/* doms_cur_mutex serializes access to doms_cur[] array */ -static DEFINE_MUTEX(doms_cur_mutex); +/* sched_domains_mutex serializes calls to arch_init_sched_domains, + * detach_destroy_domains and partition_sched_domains. + */ +static DEFINE_MUTEX(sched_domains_mutex); #ifdef CONFIG_FAIR_GROUP_SCHED #ifdef CONFIG_USER_SCHED @@ -358,21 +360,9 @@ static inline void set_task_rq(struct ta #endif } -static inline void lock_doms_cur(void) -{ - mutex_lock(&doms_cur_mutex); -} - -static inline void unlock_doms_cur(void) -{ - mutex_unlock(&doms_cur_mutex); -} - #else static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { } -static inline void lock_doms_cur(void) { } -static inline void unlock_doms_cur(void) { } #endif /* CONFIG_GROUP_SCHED */ @@ -7755,7 +7745,7 @@ void partition_sched_domains(int ndoms_n { int i, j; - lock_doms_cur(); + mutex_lock(&sched_domains_mutex); /* always unregister in case we don't destroy any domains */ unregister_sched_domain_sysctl(); @@ -7804,7 +7794,7 @@ match2: register_sched_domain_sysctl(); - unlock_doms_cur(); + mutex_unlock(&sched_domains_mutex); } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) @@ -7813,8 +7803,10 @@ int arch_reinit_sched_domains(void) int err; get_online_cpus(); + mutex_lock(&sched_domains_mutex); detach_destroy_domains(&cpu_online_map); err = arch_init_sched_domains(&cpu_online_map); + mutex_unlock(&sched_domains_mutex); put_online_cpus(); return err;
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