[3/5] memrlimit fix sleep inside sleeplock in mm_update_next_owner()
- Date: Thu, 26 Jun 2008 14:58:55 +0530
- From: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
- Subject: [3/5] memrlimit fix sleep inside sleeplock in mm_update_next_owner()
We have a sleep inside a spinlock (read side locking of tasklist_lock). We
try to acquire mmap_sem without releasing the read_lock. Since we have
the task_struct of the new process, we can release the read_lock, before
acquiring the task_lock of the chosen one.
Reported-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff -puN kernel/exit.c~memrlimit-fix-sleep-in-spinlock-bug kernel/exit.c
--- linux-2.6.26-rc5/kernel/exit.c~memrlimit-fix-sleep-in-spinlock-bug 2008-06-26 14:48:21.000000000 +0530
+++ linux-2.6.26-rc5-balbir/kernel/exit.c 2008-06-26 14:48:21.000000000 +0530
@@ -636,28 +636,24 @@ retry:
assign_new_owner:
BUG_ON(c == p);
get_task_struct(c);
+ read_unlock(&tasklist_lock);
down_write(&mm->mmap_sem);
/*
* The task_lock protects c->mm from changing.
* We always want mm->owner->mm == mm
*/
task_lock(c);
- /*
- * Delay read_unlock() till we have the task_lock()
- * to ensure that c does not slip away underneath us
- */
- read_unlock(&tasklist_lock);
if (c->mm != mm) {
task_unlock(c);
- put_task_struct(c);
up_write(&mm->mmap_sem);
+ put_task_struct(c);
goto retry;
}
cgroup_mm_owner_callbacks(mm->owner, c);
mm->owner = c;
task_unlock(c);
- put_task_struct(c);
up_write(&mm->mmap_sem);
+ put_task_struct(c);
}
#endif /* CONFIG_MM_OWNER */
_
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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