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Tejun Heo f183464684 bdi: Move cgroup bdi_writeback to a dedicated low concurrency workqueue 
From 0aa2e9b921d6db71150633ff290199554f0842a8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 23 May 2018 10:29:00 -0700

cgwb_release() punts the actual release to cgwb_release_workfn() on
system_wq.  Depending on the number of cgroups or block devices, there
can be a lot of cgwb_release_workfn() in flight at the same time.

We're periodically seeing close to 256 kworkers getting stuck with the
following stack trace and overtime the entire system gets stuck.

  [<ffffffff810ee40c>] _synchronize_rcu_expedited.constprop.72+0x2fc/0x330
  [<ffffffff810ee634>] synchronize_rcu_expedited+0x24/0x30
  [<ffffffff811ccf23>] bdi_unregister+0x53/0x290
  [<ffffffff811cd1e9>] release_bdi+0x89/0xc0
  [<ffffffff811cd645>] wb_exit+0x85/0xa0
  [<ffffffff811cdc84>] cgwb_release_workfn+0x54/0xb0
  [<ffffffff810a68d0>] process_one_work+0x150/0x410
  [<ffffffff810a71fd>] worker_thread+0x6d/0x520
  [<ffffffff810ad3dc>] kthread+0x12c/0x160
  [<ffffffff81969019>] ret_from_fork+0x29/0x40
  [<ffffffffffffffff>] 0xffffffffffffffff

The events leading to the lockup are...

1. A lot of cgwb_release_workfn() is queued at the same time and all
   system_wq kworkers are assigned to execute them.

2. They all end up calling synchronize_rcu_expedited().  One of them
   wins and tries to perform the expedited synchronization.

3. However, that invovles queueing rcu_exp_work to system_wq and
   waiting for it.  Because #1 is holding all available kworkers on
   system_wq, rcu_exp_work can't be executed.  cgwb_release_workfn()
   is waiting for synchronize_rcu_expedited() which in turn is waiting
   for cgwb_release_workfn() to free up some of the kworkers.

We shouldn't be scheduling hundreds of cgwb_release_workfn() at the
same time.  There's nothing to be gained from that.  This patch
updates cgwb release path to use a dedicated percpu workqueue with
@max_active of 1.

While this resolves the problem at hand, it might be a good idea to
isolate rcu_exp_work to its own workqueue too as it can be used from
various paths and is prone to this sort of indirect A-A deadlocks.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
 		2018-05-23 15:28:50 -06:00
..
kasan slab, slub: skip unnecessary kasan_cache_shutdown() 2018-04-05 21:36:24 -07:00
Kconfig treewide: simplify Kconfig dependencies for removed archs 2018-03-26 15:55:57 +02:00
Kconfig.debug kmemcheck: rip it out 2017-11-15 18:21:05 -08:00
Makefile mm/swap_slots.c: use conditional compilation 2018-04-05 21:36:24 -07:00
backing-dev.c bdi: Move cgroup bdi_writeback to a dedicated low concurrency workqueue 2018-05-23 15:28:50 -06:00
balloon_compaction.c virtio_balloon: fix deadlock on OOM 2017-11-14 23:57:38 +02:00
bootmem.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
cleancache.c fs: switch ->s_uuid to uuid_t 2017-06-05 16:59:12 +02:00
cma.c mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE 2018-04-11 10:28:32 -07:00
cma.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cma_debug.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compaction.c mm/cma: remove ALLOC_CMA 2018-04-11 10:28:32 -07:00
debug.c mm/debug.c: provide useful debugging information for VM_BUG 2018-01-04 16:45:09 -08:00
debug_page_ref.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dmapool.c lib/vsprintf.c: remove %Z support 2017-02-27 18:43:47 -08:00
early_ioremap.c mm/early_ioremap: Fix boot hang with earlyprintk=efi,keep 2017-12-11 14:54:44 +01:00
fadvise.c mm: add ksys_fadvise64_64() helper; remove in-kernel call to sys_fadvise64_64() 2018-04-02 20:16:10 +02:00
failslab.c mm: make should_failslab always available for fault injection 2018-04-05 21:36:26 -07:00
filemap.c mm/filemap.c: fix NULL pointer in page_cache_tree_insert() 2018-04-20 17:18:36 -07:00
frame_vector.c mm/frame_vector.c: release a semaphore in 'get_vaddr_frames()' 2017-12-14 16:00:48 -08:00
frontswap.c mm, frontswap: convert frontswap_enabled to static key 2016-07-26 16:19:19 -07:00
gup.c mm/gup.c: document return value 2018-04-13 17:10:27 -07:00
gup_benchmark.c mm/gup_benchmark: handle gup failures 2018-04-13 17:10:27 -07:00
highmem.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hmm.c mm/hmm.c: remove superfluous RCU protection around radix tree lookup 2018-04-11 10:28:31 -07:00
huge_memory.c mm: enable thp migration for shmem thp 2018-04-20 17:18:35 -07:00
hugetlb.c mm, hugetlbfs: introduce ->pagesize() to vm_operations_struct 2018-04-05 21:36:26 -07:00
hugetlb_cgroup.c mm, hugetlb_cgroup: round limit_in_bytes down to hugepage size 2016-05-20 17:58:30 -07:00
hwpoison-inject.c mm/memory_failure: Remove unused trapno from memory_failure 2018-01-23 12:17:42 -06:00
init-mm.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
internal.h mm/cma: remove ALLOC_CMA 2018-04-11 10:28:32 -07:00
interval_tree.c mm/interval_tree.c: use vma_pages() helper 2018-01-31 17:18:37 -08:00
khugepaged.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
kmemleak-test.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
kmemleak.c mm: kernel-doc: add missing parameter descriptions 2018-04-05 21:36:27 -07:00
ksm.c mm/ksm.c: fix inconsistent accounting of zero pages 2018-04-11 10:28:31 -07:00
list_lru.c mm: make counting of list_lru_one::nr_items lockless 2018-04-05 21:36:27 -07:00
maccess.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
madvise.c mm/memory_failure: Remove unused trapno from memory_failure 2018-01-23 12:17:42 -06:00
memblock.c powerpc updates for 4.17 2018-04-07 12:08:19 -07:00
memcontrol.c mm: memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create() 2018-04-20 17:18:36 -07:00
memory-failure.c mm, migrate: remove reason argument from new_page_t 2018-04-11 10:28:32 -07:00
memory.c mm: swap: unify cluster-based and vma-based swap readahead 2018-04-05 21:36:25 -07:00
memory_hotplug.c mm: unclutter THP migration 2018-04-11 10:28:32 -07:00
mempolicy.c mm: unclutter THP migration 2018-04-11 10:28:32 -07:00
mempool.c mempool: Add mempool_init()/mempool_exit() 2018-05-14 13:14:23 -06:00
memtest.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
migrate.c mm: enable thp migration for shmem thp 2018-04-20 17:18:35 -07:00
mincore.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mlock.c mm, mlock, vmscan: no more skipping pagevecs 2018-02-21 15:35:42 -08:00
mm_init.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
mmap.c x86/pti: Filter at vma->vm_page_prot population 2018-04-25 11:02:51 +02:00
mmu_context.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
mmu_notifier.c mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks 2018-01-31 17:18:38 -08:00
mmzone.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mprotect.c sched/numa: avoid trapping faults and attempting migration of file-backed dirty pages 2018-04-11 10:28:31 -07:00
mremap.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
msync.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nobootmem.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nommu.c mm/nommu: remove description of alloc_vm_area 2018-04-05 21:36:26 -07:00
oom_kill.c mm,oom_reaper: check for MMF_OOM_SKIP before complaining 2018-04-05 21:36:27 -07:00
page-writeback.c writeback: safer lock nesting 2018-04-20 17:18:35 -07:00
page_alloc.c xen, mm: allow deferred page initialization for xen pv domains 2018-04-11 10:28:38 -07:00
page_counter.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
page_ext.c mm/page_ext.c: make page_ext_init a noop when CONFIG_PAGE_EXTENSION but nothing uses it 2018-01-31 17:18:39 -08:00
page_idle.c mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one() 2018-04-05 21:36:25 -07:00
page_io.c block: convert to bio_first_bvec_all & bio_first_page_all 2018-01-06 09:18:00 -07:00
page_isolation.c mm, migrate: remove reason argument from new_page_t 2018-04-11 10:28:32 -07:00
page_owner.c mm/page_owner.c: make early_page_owner_param() __init 2018-04-05 21:36:26 -07:00
page_poison.c mm/page_poison.c: make early_page_poison_param() __init 2018-04-05 21:36:26 -07:00
page_vma_mapped.c mm, page_vma_mapped: Introduce pfn_in_hpage() 2018-01-22 12:15:57 -08:00
pagewalk.c mm: kernel-doc: add missing parameter descriptions 2018-04-05 21:36:27 -07:00
percpu-internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
percpu-km.c percpu: allow select gfp to be passed to underlying allocators 2018-02-18 05:33:01 -08:00
percpu-stats.c mm: reuse DEFINE_SHOW_ATTRIBUTE() macro 2018-04-05 21:36:25 -07:00
percpu-vm.c percpu: allow select gfp to be passed to underlying allocators 2018-02-18 05:33:01 -08:00
percpu.c arch: remove obsolete architecture ports 2018-04-02 20:20:12 -07:00
pgtable-generic.c mm: do not lose dirty and accessed bits in pmdp_invalidate() 2018-01-31 17:18:38 -08:00
process_vm_access.c mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors 2018-02-06 18:32:48 -08:00
quicklist.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
readahead.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
rmap.c mm: enable thp migration for shmem thp 2018-04-20 17:18:35 -07:00
rodata_test.c mm: fix RODATA_TEST failure "rodata_test: test data was not read only" 2017-10-03 17:54:24 -07:00
shmem.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
slab.c mm, slab: reschedule cache_reap() on the same CPU 2018-04-13 17:10:27 -07:00
slab.h slab, slub: skip unnecessary kasan_cache_shutdown() 2018-04-05 21:36:24 -07:00
slab_common.c mm: make should_failslab always available for fault injection 2018-04-05 21:36:26 -07:00
slob.c slab, slub, slob: add slab_flags_t 2017-11-15 18:21:01 -08:00
slub.c kasan, slub: fix handling of kasan_slab_free hook 2018-04-11 10:28:32 -07:00
sparse-vmemmap.c mm: merge vmem_altmap_alloc into altmap_alloc_block_buf 2018-01-08 11:46:23 -08:00
sparse.c mm/memory_hotplug: optimize memory hotplug 2018-04-05 21:36:25 -07:00
swap.c mm/swap.c: remove @cold parameter description for release_pages() 2018-04-05 21:36:26 -07:00
swap_cgroup.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swap_slots.c mm/swap_slots.c: use conditional compilation 2018-04-05 21:36:24 -07:00
swap_state.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
swapfile.c mm/swapfile.c: make pointer swap_avail_heads static 2018-04-11 10:28:32 -07:00
truncate.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
usercopy.c usercopy: WARN() on slab cache usercopy region violations 2018-01-15 12:07:48 -08:00
userfaultfd.c mm/userfaultfd.c: remove duplicate include 2018-02-06 18:32:47 -08:00
util.c mm/gup.c: document return value 2018-04-13 17:10:27 -07:00
vmacache.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vmalloc.c vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems 2018-02-21 15:35:43 -08:00
vmpressure.c mm, vmpressure: pass-through notification support 2017-07-10 16:32:31 -07:00
vmscan.c mm,vmscan: Allow preallocating memory for register_shrinker(). 2018-04-16 02:06:47 -04:00
vmstat.c mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES 2018-04-11 10:28:29 -07:00
workingset.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
z3fold.c mm/z3fold.c: use gfpflags_allow_blocking 2018-04-11 10:28:31 -07:00
zbud.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
zpool.c mm/zpool.c: zpool_evictable: fix mismatch in parameter name and kernel-doc 2018-02-21 15:35:43 -08:00
zsmalloc.c mm: kernel-doc: add missing parameter descriptions 2018-04-05 21:36:27 -07:00
zswap.c mm, swap, frontswap: fix THP swap if frontswap enabled 2018-02-21 15:35:43 -08:00