aboutsummaryrefslogtreecommitdiff
path: root/kernel/cgroup.c
diff options
context:
space:
mode:
authorDave Anderson <anderson@redhat.com>2010-01-08 14:42:50 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2010-01-18 10:19:32 -0800
commit21f7654aa8eac2e3c47097497aee440c222bd9ed (patch)
treee04257f8404928495e9689707e5a165f40525cb7 /kernel/cgroup.c
parent6abb6ac30148ca47ff66c917ecd83df975daccbf (diff)
cgroups: fix 2.6.32 regression causing BUG_ON() in cgroup_diput()
commit bd4f490a079730aadfaf9a728303ea0135c01945 upstream. The LTP cgroup test suite generates a "kernel BUG at kernel/cgroup.c:790!" here in cgroup_diput(): /* * if we're getting rid of the cgroup, refcount should ensure * that there are no pidlists left. */ BUG_ON(!list_empty(&cgrp->pidlists)); The cgroup pidlist rework in 2.6.32 generates the BUG_ON, which is caused when pidlist_array_load() calls cgroup_pidlist_find(): (1) if a matching cgroup_pidlist is found, it down_write's the mutex of the pre-existing cgroup_pidlist, and increments its use_count. (2) if no matching cgroup_pidlist is found, then a new one is allocated, it down_write's its mutex, and the use_count is set to 0. (3) the matching, or new, cgroup_pidlist gets returned back to pidlist_array_load(), which increments its use_count -- regardless whether new or pre-existing -- and up_write's the mutex. So if a matching list is ever encountered by cgroup_pidlist_find() during the life of a cgroup directory, it results in an inflated use_count value, preventing it from ever getting released by cgroup_release_pid_array(). Then if the directory is subsequently removed, cgroup_diput() hits the BUG_ON() when it finds that the directory's cgroup is still populated with a pidlist. The patch simply removes the use_count increment when a matching pidlist is found by cgroup_pidlist_find(), because it gets bumped by the calling pidlist_array_load() function while still protected by the list's mutex. Signed-off-by: Dave Anderson <anderson@redhat.com> Reviewed-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Ben Blum <bblum@andrew.cmu.edu> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0249f4be9b5..1fbcc748044 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2468,7 +2468,6 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
/* make sure l doesn't vanish out from under us */
down_write(&l->mutex);
mutex_unlock(&cgrp->pidlist_mutex);
- l->use_count++;
return l;
}
}