The patch titled Subject: slub: drop mutex before deleting sysfs entry has been added to the -mm tree. Its filename is slub-drop-mutex-before-deleting-sysfs-entry.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Glauber Costa <glommer@xxxxxxxxxxxxx> Subject: slub: drop mutex before deleting sysfs entry Sasha Levin recently reported a lockdep problem resulting from the new attribute propagation introduced by kmemcg series. In short, slab_mutex will be called from within the sysfs attribute store function. This will create a dependency, that will later be held backwards when a cache is destroyed - since destruction occurs with the slab_mutex held, and then calls in to the sysfs directory removal function. In this patch, I propose to adopt a strategy close to what __kmem_cache_create does before calling sysfs_slab_add, and release the lock before the call to sysfs_slab_remove. This is pretty much the last operation in the kmem_cache_shutdown() path, so we could do better by splitting this and moving this call alone to later on. This will fit nicely when sysfs handling is consistent between all caches, but will look weird now. Lockdep info: [ 351.935003] ====================================================== [ 351.937693] [ INFO: possible circular locking dependency detected ] [ 351.939720] 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117 Tainted: G W [ 351.942444] ------------------------------------------------------- [ 351.943528] trinity-child13/6961 is trying to acquire lock: [ 351.943528] (s_active#43){++++.+}, at: [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60 [ 351.943528] [ 351.943528] but task is already holding lock: [ 351.943528] (slab_mutex){+.+.+.}, at: [<ffffffff81228a42>] kmem_cache_destroy+0x22/0xe0 [ 351.943528] [ 351.943528] which lock already depends on the new lock. [ 351.943528] [ 351.943528] [ 351.943528] the existing dependency chain (in reverse order) is: [ 351.943528] -> #1 (slab_mutex){+.+.+.}: [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240 [ 351.960334] [<ffffffff83a944d9>] __mutex_lock_common+0x59/0x5a0 [ 351.960334] [<ffffffff83a94a5f>] mutex_lock_nested+0x3f/0x50 [ 351.960334] [<ffffffff81256a6e>] slab_attr_store+0xde/0x110 [ 351.960334] [<ffffffff812f820a>] sysfs_write_file+0xfa/0x150 [ 351.960334] [<ffffffff8127a220>] vfs_write+0xb0/0x180 [ 351.960334] [<ffffffff8127a540>] sys_pwrite64+0x60/0xb0 [ 351.960334] [<ffffffff83a99298>] tracesys+0xe1/0xe6 [ 351.960334] -> #0 (s_active#43){++++.+}: [ 351.960334] [<ffffffff811825af>] __lock_acquire+0x14df/0x1ca0 [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240 [ 351.960334] [<ffffffff812f9272>] sysfs_deactivate+0x122/0x1a0 [ 351.960334] [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60 [ 351.960334] [<ffffffff812fa369>] sysfs_remove_dir+0x89/0xd0 [ 351.960334] [<ffffffff819e1d96>] kobject_del+0x16/0x40 [ 351.960334] [<ffffffff8125ed40>] __kmem_cache_shutdown+0x40/0x60 [ 351.960334] [<ffffffff81228a60>] kmem_cache_destroy+0x40/0xe0 [ 351.960334] [<ffffffff82b21058>] mon_text_release+0x78/0xe0 [ 351.960334] [<ffffffff8127b3b2>] __fput+0x122/0x2d0 [ 351.960334] [<ffffffff8127b569>] ____fput+0x9/0x10 [ 351.960334] [<ffffffff81131b4e>] task_work_run+0xbe/0x100 [ 351.960334] [<ffffffff81110742>] do_exit+0x432/0xbd0 [ 351.960334] [<ffffffff81110fa4>] do_group_exit+0x84/0xd0 [ 351.960334] [<ffffffff8112431d>] get_signal_to_deliver+0x81d/0x930 [ 351.960334] [<ffffffff8106d5aa>] do_signal+0x3a/0x950 [ 351.960334] [<ffffffff8106df1e>] do_notify_resume+0x3e/0x90 [ 351.960334] [<ffffffff83a993aa>] int_signal+0x12/0x17 [ 351.960334] [ 351.960334] other info that might help us debug this: [ 351.960334] [ 351.960334] Possible unsafe locking scenario: [ 351.960334] [ 351.960334] CPU0 CPU1 [ 351.960334] ---- ---- [ 351.960334] lock(slab_mutex); [ 351.960334] lock(s_active#43); [ 351.960334] lock(slab_mutex); [ 351.960334] lock(s_active#43); [ 351.960334] [ 351.960334] *** DEADLOCK *** [ 351.960334] [ 351.960334] 2 locks held by trinity-child13/6961: [ 351.960334] #0: (mon_lock){+.+.+.}, at: [<ffffffff82b21005>] mon_text_release+0x25/0xe0 [ 351.960334] #1: (slab_mutex){+.+.+.}, at: [<ffffffff81228a42>] kmem_cache_destroy+0x22/0xe0 [ 351.960334] [ 351.960334] stack backtrace: [ 351.960334] Pid: 6961, comm: trinity-child13 Tainted: G W 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117 [ 351.960334] Call Trace: [ 351.960334] [<ffffffff83a3c736>] print_circular_bug+0x1fb/0x20c [ 351.960334] [<ffffffff811825af>] __lock_acquire+0x14df/0x1ca0 [ 351.960334] [<ffffffff81184045>] ? debug_check_no_locks_freed+0x185/0x1e0 [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240 [ 351.960334] [<ffffffff812f9e11>] ? sysfs_addrm_finish+0x31/0x60 [ 351.960334] [<ffffffff812f9272>] sysfs_deactivate+0x122/0x1a0 [ 351.960334] [<ffffffff812f9e11>] ? sysfs_addrm_finish+0x31/0x60 [ 351.960334] [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60 [ 351.960334] [<ffffffff812fa369>] sysfs_remove_dir+0x89/0xd0 [ 351.960334] [<ffffffff819e1d96>] kobject_del+0x16/0x40 [ 351.960334] [<ffffffff8125ed40>] __kmem_cache_shutdown+0x40/0x60 [ 351.960334] [<ffffffff81228a60>] kmem_cache_destroy+0x40/0xe0 [ 351.960334] [<ffffffff82b21058>] mon_text_release+0x78/0xe0 [ 351.960334] [<ffffffff8127b3b2>] __fput+0x122/0x2d0 [ 351.960334] [<ffffffff8127b569>] ____fput+0x9/0x10 [ 351.960334] [<ffffffff81131b4e>] task_work_run+0xbe/0x100 [ 351.960334] [<ffffffff81110742>] do_exit+0x432/0xbd0 [ 351.960334] [<ffffffff811243b9>] ? get_signal_to_deliver+0x8b9/0x930 [ 351.960334] [<ffffffff8117d402>] ? get_lock_stats+0x22/0x70 [ 351.960334] [<ffffffff8117d48e>] ? put_lock_stats.isra.16+0xe/0x40 [ 351.960334] [<ffffffff83a977fb>] ? _raw_spin_unlock_irq+0x2b/0x80 [ 351.960334] [<ffffffff81110fa4>] do_group_exit+0x84/0xd0 [ 351.960334] [<ffffffff8112431d>] get_signal_to_deliver+0x81d/0x930 [ 351.960334] [<ffffffff8117d48e>] ? put_lock_stats.isra.16+0xe/0x40 [ 351.960334] [<ffffffff8106d5aa>] do_signal+0x3a/0x950 [ 351.960334] [<ffffffff811c8b33>] ? rcu_cleanup_after_idle+0x23/0x170 [ 351.960334] [<ffffffff811cc1c4>] ? rcu_eqs_exit_common+0x64/0x3a0 [ 351.960334] [<ffffffff811caa5d>] ? rcu_user_enter+0x10d/0x140 [ 351.960334] [<ffffffff811cc8d5>] ? rcu_user_exit+0xc5/0xf0 [ 351.960334] [<ffffffff8106df1e>] do_notify_resume+0x3e/0x90 [ 351.960334] [<ffffffff83a993aa>] int_signal+0x12/0x17 Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx> Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxx> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff -puN mm/slub.c~slub-drop-mutex-before-deleting-sysfs-entry mm/slub.c --- a/mm/slub.c~slub-drop-mutex-before-deleting-sysfs-entry +++ a/mm/slub.c @@ -3189,8 +3189,19 @@ int __kmem_cache_shutdown(struct kmem_ca { int rc = kmem_cache_close(s); - if (!rc) + if (!rc) { + /* + * We do the same lock strategy around sysfs_slab_add, see + * __kmem_cache_create. Because this is pretty much the last + * operation we do and the lock will be released shortly after + * that in slab_common.c, we could just move sysfs_slab_remove + * to a later point in common code. We should do that when we + * have a common sysfs framework for all allocators. + */ + mutex_unlock(&slab_mutex); sysfs_slab_remove(s); + mutex_lock(&slab_mutex); + } return rc; } _ Patches currently in -mm which might be from glommer@xxxxxxxxxxxxx are linux-next.patch memcg-make-it-possible-to-use-the-stock-for-more-than-one-page.patch memcg-reclaim-when-more-than-one-page-needed.patch memcg-change-defines-to-an-enum.patch memcg-kmem-accounting-basic-infrastructure.patch mm-add-a-__gfp_kmemcg-flag.patch memcg-kmem-controller-infrastructure.patch memcg-kmem-controller-infrastructure-replace-__always_inline-with-plain-inline.patch mm-allocate-kernel-pages-to-the-right-memcg.patch res_counter-return-amount-of-charges-after-res_counter_uncharge.patch memcg-kmem-accounting-lifecycle-management.patch memcg-use-static-branches-when-code-not-in-use.patch memcg-allow-a-memcg-with-kmem-charges-to-be-destructed.patch memcg-execute-the-whole-memcg-freeing-in-free_worker.patch fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs.patch memcg-add-documentation-about-the-kmem-controller.patch slab-slub-struct-memcg_params.patch slab-annotate-on-slab-caches-nodelist-locks.patch slab-slub-consider-a-memcg-parameter-in-kmem_create_cache.patch memcg-allocate-memory-for-memcg-caches-whenever-a-new-memcg-appears.patch memcg-allocate-memory-for-memcg-caches-whenever-a-new-memcg-appears-simplify-ida-initialization.patch memcg-infrastructure-to-match-an-allocation-to-the-right-cache.patch memcg-skip-memcg-kmem-allocations-in-specified-code-regions.patch memcg-skip-memcg-kmem-allocations-in-specified-code-regions-remove-test-for-current-mm-in-memcg_stop-resume_kmem_account.patch slb-always-get-the-cache-from-its-page-in-kmem_cache_free.patch slb-allocate-objects-from-memcg-cache.patch memcg-destroy-memcg-caches.patch memcg-destroy-memcg-caches-move-include-of-workqueueh-to-top-of-slabh-file.patch memcg-slb-track-all-the-memcg-children-of-a-kmem_cache.patch memcg-slb-shrink-dead-caches.patch memcg-slb-shrink-dead-caches-get-rid-of-once-per-second-cache-shrinking-for-dead-memcgs.patch memcg-aggregate-memcg-cache-values-in-slabinfo.patch slab-propagate-tunable-values.patch slub-slub-specific-propagation-changes.patch slub-slub-specific-propagation-changes-fix.patch kmem-add-slab-specific-documentation-about-the-kmem-controller.patch memcg-add-comments-clarifying-aspects-of-cache-attribute-propagation.patch slub-drop-mutex-before-deleting-sysfs-entry.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