[PATCH] slab: Fix hang when creating sysfs entries

[Sasha Levin]

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@xxxxxxxxx>
---
 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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