Message-ID: <CAMuHMdUJSfrZ=2zy88_zojDek3CHEWKhv_qoJAVgDpPWz8V=Ew@mail.gmail.com>
Date:   Tue, 18 Apr 2017 21:56:56 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: "mm: move pcp and lru-pcp draining into single wq" broke resume from s2ram

Hi all,

On Sat, Apr 8, 2017 at 10:48 AM, Linux Kernel Mailing List
<linux-kernel@...r.kernel.org> wrote:
> Web:        https://git.kernel.org/torvalds/c/ce612879ddc78ea7e4de4be80cba4ebf9caa07ee
> Commit:     ce612879ddc78ea7e4de4be80cba4ebf9caa07ee
> Parent:     cdcf4330d5660998d06fcd899b443693ab3d652f
> Refname:    refs/heads/master
> Author:     Michal Hocko <mhocko@...e.com>
> AuthorDate: Fri Apr 7 16:05:05 2017 -0700
> Committer:  Linus Torvalds <torvalds@...ux-foundation.org>
> CommitDate: Sat Apr 8 00:47:49 2017 -0700
>
>     mm: move pcp and lru-pcp draining into single wq
>
>     We currently have 2 specific WQ_RECLAIM workqueues in the mm code.
>     vmstat_wq for updating pcp stats and lru_add_drain_wq dedicated to drain
>     per cpu lru caches.  This seems more than necessary because both can run
>     on a single WQ.  Both do not block on locks requiring a memory
>     allocation nor perform any allocations themselves.  We will save one
>     rescuer thread this way.
>
>     On the other hand drain_all_pages() queues work on the system wq which
>     doesn't have rescuer and so this depend on memory allocation (when all
>     workers are stuck allocating and new ones cannot be created).
>
>     Initially we thought this would be more of a theoretical problem but
>     Hugh Dickins has reported:
>
>     : 4.11-rc has been giving me hangs after hours of swapping load.  At
>     : first they looked like memory leaks ("fork: Cannot allocate memory");
>     : but for no good reason I happened to do "cat /proc/sys/vm/stat_refresh"
>     : before looking at /proc/meminfo one time, and the stat_refresh stuck
>     : in D state, waiting for completion of flush_work like many kworkers.
>     : kthreadd waiting for completion of flush_work in drain_all_pages().
>
>     This worker should be using WQ_RECLAIM as well in order to guarantee a
>     forward progress.  We can reuse the same one as for lru draining and
>     vmstat.
>
>     Link: http://lkml.kernel.org/r/20170307131751.24936-1-mhocko@kernel.org
>     Signed-off-by: Michal Hocko <mhocko@...e.com>
>     Suggested-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
>     Acked-by: Vlastimil Babka <vbabka@...e.cz>
>     Acked-by: Mel Gorman <mgorman@...e.de>
>     Tested-by: Yang Li <pku.leo@...il.com>
>     Tested-by: Hugh Dickins <hughd@...gle.com>
>     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

This commit broke resume from s2ram on some of my Renesas ARM boards.
On some boards the hang is 100% reproducible, on others it's intermittent
(which was a PITA, as I had to bisect another independent s2ram bug as well).

On r8a7791/koelsch:

--- /tmp/good   2017-04-18 21:47:04.457156167 +0200
+++ /tmp/bad    2017-04-18 21:43:26.215240325 +0200
@@ -13,11 +13,178 @@ Enabling non-boot CPUs ...
 CPU1 is up
 PM: noirq resume of devices complete after N.N msecs
 PM: early resume of devices complete after N.N msecs
-Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: attached PHY driver
[Micrel KSZ8041RNLI] (mii_bus:phy_addr=ee700000.ethernet-ffffffff:01,
irq=-1)
-PM: resume of devices complete after N.N msecs
-PM: resume devices took N.N seconds
-PM: Finishing wakeup.
-Restarting tasks ... done.
-ata1: link resume succeeded after 1 retries
-ata1: SATA link down (SStatus 0 SControl 300)
-sh-eth ee700000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
+INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
+      Not tainted 4.11.0-rc7-koelsch-00426-g70412b99f7936b37 #3470
+"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
+kworker/u4:0    D    0     5      2 0x00000000
+Workqueue: events_unbound async_run_entry_fn
+[<c0712c58>] (__schedule) from [<c0712f7c>] (schedule+0xb0/0xcc)
+[<c0712f7c>] (schedule) from [<c0717140>] (schedule_timeout+0x18/0x1f4)
+[<c0717140>] (schedule_timeout) from [<c07139f8>] (wait_for_common+0x100/0x19c)
+[<c07139f8>] (wait_for_common) from [<c04d8488>]
(dpm_wait_for_superior+0x14/0x5c)
+[<c04d8488>] (dpm_wait_for_superior) from [<c04d8aa4>]
(device_resume+0x40/0x1a0)
+[<c04d8aa4>] (device_resume) from [<c04d8c1c>] (async_resume+0x18/0x44)
+[<c04d8c1c>] (async_resume) from [<c023db34>] (async_run_entry_fn+0x44/0x114)
+[<c023db34>] (async_run_entry_fn) from [<c0236544>]
(process_one_work+0x1cc/0x31c)
+[<c0236544>] (process_one_work) from [<c0236ca0>] (worker_thread+0x2b8/0x3f0)
+[<c0236ca0>] (worker_thread) from [<c023b240>] (kthread+0x120/0x140)
+[<c023b240>] (kthread) from [<c0206d68>] (ret_from_fork+0x14/0x2c)
+INFO: task kworker/u4:1:125 blocked for more than 120 seconds.
+      Not tainted 4.11.0-rc7-koelsch-00426-g70412b99f7936b37 #3470
+"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
+kworker/u4:1    D    0   125      2 0x00000000
+Workqueue: events_unbound async_run_entry_fn
+[<c0712c58>] (__schedule) from [<c0712f7c>] (schedule+0xb0/0xcc)
+[<c0712f7c>] (schedule) from [<c0717140>] (schedule_timeout+0x18/0x1f4)
+[<c0717140>] (schedule_timeout) from [<c07139f8>] (wait_for_common+0x100/0x19c)
+[<c07139f8>] (wait_for_common) from [<c04d8488>]
(dpm_wait_for_superior+0x14/0x5c)
+[<c04d8488>] (dpm_wait_for_superior) from [<c04d8aa4>]
(device_resume+0x40/0x1a0)
+[<c04d8aa4>] (device_resume) from [<c04d8c1c>] (async_resume+0x18/0x44)
+[<c04d8c1c>] (async_resume) from [<c023db34>] (async_run_entry_fn+0x44/0x114)
+[<c023db34>] (async_run_entry_fn) from [<c0236544>]
(process_one_work+0x1cc/0x31c)
+[<c0236544>] (process_one_work) from [<c0236ca0>] (worker_thread+0x2b8/0x3f0)
+[<c0236ca0>] (worker_thread) from [<c023b240>] (kthread+0x120/0x140)
+[<c023b240>] (kthread) from [<c0206d68>] (ret_from_fork+0x14/0x2c)
...

On r8a7795/salvator-x, where I have working lockdep:

PM: noirq resume of devices complete after 131.415 msecs
PM: early resume of devices complete after 8.894 msecs
INFO: task kworker/u16:2:276 blocked for more than 120 seconds.
      Not tainted 4.11.0-rc7-salvator-x-06706-g70412b99f7936b37 #1220
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u16:2   D    0   276      2 0x00000000
Workqueue: events_unbound async_run_entry_fn
Call trace:
[<ffffff800808612c>] __switch_to+0xa0/0xac
[<ffffff800866df14>] __schedule+0x70c/0xb88
[<ffffff800866e414>] schedule+0x84/0xa4
[<ffffff800867287c>] schedule_timeout+0x30/0x400
[<ffffff800866ee94>] wait_for_common+0x164/0x1a8
[<ffffff800866eeec>] wait_for_completion+0x14/0x1c
[<ffffff80083d3f84>] dpm_wait+0x30/0x38
[<ffffff80083d3ff8>] dpm_wait_for_superior+0x28/0x7c
[<ffffff80083d490c>] device_resume+0x44/0x190
[<ffffff80083d4a7c>] async_resume+0x24/0x54
[<ffffff80080d5360>] async_run_entry_fn+0x4c/0x12c
[<ffffff80080cb59c>] process_one_work+0x340/0x66c
[<ffffff80080cc9ec>] worker_thread+0x274/0x39c
[<ffffff80080d2004>] kthread+0x120/0x128
[<ffffff8008083090>] ret_from_fork+0x10/0x40

Showing all locks held in the system:
2 locks held by khungtaskd/52:
 #0:  (rcu_read_lock){......}, at: [<ffffff80081436cc>] watchdog+0xc0/0x618
 #1:  (tasklist_lock){.+.+..}, at: [<ffffff80080fb5f0>]
debug_show_all_locks+0x68/0x18c
2 locks held by kworker/u16:2/276:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:3/291:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
8 locks held by s2ram/1899:
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffff80081ca1a4>] vfs_write+0xa8/0x15c
 #1:  (&of->mutex){+.+.+.}, at: [<ffffff8008245964>] kernfs_fop_write+0xf0/0x194
 #2:  (s_active#48){.+.+.+}, at: [<ffffff800824596c>]
kernfs_fop_write+0xf8/0x194
 #3:  (pm_mutex){+.+.+.}, at: [<ffffff80081059a4>] pm_suspend+0x16c/0xabc
 #4:  (&dev->mutex){......}, at: [<ffffff80083d4920>] device_resume+0x58/0x190
 #5:  (cma_mutex){+.+...}, at: [<ffffff80081c516c>] cma_alloc+0x150/0x374
 #6:  (lock){+.+...}, at: [<ffffff800818b8ec>] lru_add_drain_all+0x4c/0x1b4
 #7:  (cpu_hotplug.dep_map){++++++}, at: [<ffffff80080ab8f4>]
get_online_cpus+0x3c/0x9c
2 locks held by kworker/u16:1/1918:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:4/1919:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:5/1920:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:7/1922:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:9/1924:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:10/1925:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:11/1926:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:12/1927:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:13/1928:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:14/1929:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
2 locks held by kworker/u16:16/1931:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c
 #1:  ((&entry->work)){+.+...}, at: [<ffffff80080cb424>]
process_one_work+0x1c8/0x66c

Thanks for your comments!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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