The patch titled cgroup: fix potential deadlock in pre_destroy has been removed from the -mm tree. Its filename was cgroup-fix-potential-deadlock-in-pre_destroy-v2.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: cgroup: fix potential deadlock in pre_destroy From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> As Balbir pointed out, memcg's pre_destroy handler has potential deadlock. It has following lock sequence. cgroup_mutex (cgroup_rmdir) -> pre_destroy -> mem_cgroup_pre_destroy-> force_empty -> cpu_hotplug.lock. (lru_add_drain_all-> schedule_work-> get_online_cpus) But, cpuset has following. cpu_hotplug.lock (call notifier) -> cgroup_mutex. (within notifier) Then, this lock sequence should be fixed. Considering how pre_destroy works, it's not necessary to holding cgroup_mutex() while calling it. As a side effect, we don't have to wait at this mutex while memcg's force_empty works.(it can be long when there are tons of pages.) Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx> Cc: Paul Menage <menage@xxxxxxxxxx> Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/cgroup.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff -puN kernel/cgroup.c~cgroup-fix-potential-deadlock-in-pre_destroy-v2 kernel/cgroup.c --- a/kernel/cgroup.c~cgroup-fix-potential-deadlock-in-pre_destroy-v2 +++ a/kernel/cgroup.c @@ -2472,10 +2472,7 @@ static int cgroup_rmdir(struct inode *un mutex_unlock(&cgroup_mutex); return -EBUSY; } - - parent = cgrp->parent; - root = cgrp->root; - sb = root->sb; + mutex_unlock(&cgroup_mutex); /* * Call pre_destroy handlers of subsys. Notify subsystems @@ -2483,7 +2480,14 @@ static int cgroup_rmdir(struct inode *un */ cgroup_call_pre_destroy(cgrp); - if (cgroup_has_css_refs(cgrp)) { + mutex_lock(&cgroup_mutex); + parent = cgrp->parent; + root = cgrp->root; + sb = root->sb; + + if (atomic_read(&cgrp->count) + || !list_empty(&cgrp->children) + || cgroup_has_css_refs(cgrp)) { mutex_unlock(&cgroup_mutex); return -EBUSY; } _ Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are origin.patch vmscan-evict-streaming-io-first.patch quota-cleanup-move-export_symbol-immediatlely-next-to-the-functions-variables-fix.patch cgroups-make-cgroup-config-a-submenu.patch memcg-introduce-charge-commit-cancel-style-of-functions.patch memcg-introduce-charge-commit-cancel-style-of-functions-fix.patch memcg-fix-gfp_mask-of-callers-of-charge.patch memcg-simple-migration-handling.patch memcg-do-not-recalculate-section-unnecessarily-in-init_section_page_cgroup.patch memcg-move-all-acccounts-to-parent-at-rmdir.patch memcg-memory-hotplug-fix-for-notifier-callback.patch memcg-reduce-size-of-mem_cgroup-by-using-nr_cpu_ids.patch memcg-new-force_empty-to-free-pages-under-group.patch memcg-handle-swap-caches.patch memcg-handle-swap-caches-build-fix.patch memcg-memswap-controller-kconfig.patch memcg-swap-cgroup-for-remembering-usage.patch memcg-swap-cgroup-for-remembering-usage-fix.patch memcg-swap-cgroup-for-remembering-usage-fix-4.patch memcg-memswap-controller-core.patch memcg-memswap-controller-core-make-resize-limit-hold-mutex.patch memcg-synchronized-lru.patch memcg-add-mem_cgroup_disabled.patch memcg-add-mem_cgroup_disabled-fix.patch memory-cgroup-hierarchy-documentation-v4.patch memory-cgroup-resource-counters-for-hierarchy-v4.patch memory-cgroup-resource-counters-for-hierarchy-v4-checkpatch-fixes.patch memory-cgroup-hierarchical-reclaim-v4.patch memory-cgroup-hierarchical-reclaim-v4-checkpatch-fixes.patch memory-cgroup-hierarchy-feature-selector-v4.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