lkml.org 
[lkml]   [2008]   [Apr]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] sched: missing locking in sched_domains code
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;

\
 
 \ /
  Last update: 2008-04-28 11:21    [W:0.053 / U:0.540 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site