Messages in this thread Patch in this message | | | Subject | Re: Hung task when calling clone() due to netfilter/slab | From | Sasha Levin <> | Date | Sun, 15 Jan 2012 14:59:44 +0200 |
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On Sat, 2012-01-14 at 18:10 +0100, Eric Dumazet wrote: > Apparently SLUB calls sysfs_slab_add() from kmem_cache_create() while > still holding slub_lock. > > So if the task launched needs to "cat /proc/slabinfo" or anything > needing slub_lock, its a deadlock.
I've made the following patch to test it, It doesn't look like it's the correct solution, but it verifies that the problem is there (it works well with the patch).
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From cc4874b491b8e5d9d1ea5bf2032413efdbddced8 Mon Sep 17 00:00:00 2001 From: Sasha Levin <levinsasha928@gmail.com> Date: Sun, 15 Jan 2012 14:55:03 +0200 Subject: [PATCH] slab: Fix hang when creating sysfs entries
This patch fixes the hang which happens when we create a sysfs entry and call back to userspace. If the usermode helper tries to do anything which involves slub_lock we will hang since slub_lock is already held.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com> --- mm/slub.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index 4907563..6948327 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5283,7 +5283,9 @@ static int sysfs_slab_add(struct kmem_cache *s) kobject_put(&s->kobj); return err; } + up_write(&slub_lock); kobject_uevent(&s->kobj, KOBJ_ADD); + down_write(&slub_lock); if (!unmergeable) { /* Setup first alias */ sysfs_slab_alias(s, s->name); -- 1.7.8.3
--
Sasha.
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