The patch titled cgroups: fix 2.6.32 regression causing BUG_ON() in cgroup_diput() has been removed from the -mm tree. Its filename was cgroups-fix-2632-regression-causing-bug_on-in-cgroup_diput.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: cgroups: fix 2.6.32 regression causing BUG_ON() in cgroup_diput() From: Dave Anderson <anderson@xxxxxxxxxx> 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@xxxxxxxxxx> Reviewed-by: Li Zefan <lizf@xxxxxxxxxxxxxx> Acked-by: Ben Blum <bblum@xxxxxxxxxxxxxx> Cc: Paul Menage <menage@xxxxxxxxxx> Cc: <stable@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/cgroup.c | 1 - 1 file changed, 1 deletion(-) diff -puN kernel/cgroup.c~cgroups-fix-2632-regression-causing-bug_on-in-cgroup_diput kernel/cgroup.c --- a/kernel/cgroup.c~cgroups-fix-2632-regression-causing-bug_on-in-cgroup_diput +++ a/kernel/cgroup.c @@ -2468,7 +2468,6 @@ static struct cgroup_pidlist *cgroup_pid /* make sure l doesn't vanish out from under us */ down_write(&l->mutex); mutex_unlock(&cgrp->pidlist_mutex); - l->use_count++; return l; } } _ Patches currently in -mm which might be from anderson@xxxxxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html