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Date: Mon, 18 Dec 2017 18:35:11 +0100
From: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To: Daniel Vetter <daniel.vetter@...ll.ch>,
kernel test robot <fengguang.wu@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: LKP <lkp@...org>, wfg@...ux.intel.com,
intel-gfx <intel-gfx@...ts.freedesktop.org>
Subject: Re: 995d11c4c0 ("drm: rework delayed connector cleanup in .."):
WARNING: possible circular locking dependency detected
Op 18-12-17 om 08:08 schreef Daniel Vetter:
> Hm, the bisect looks funny. Only way I can explain that is that my
> patch fixed a pre-existing lockdep splat, and uncovered the issue in
> the ww-mutex self tests. That one is uncovered by the new
> cross-release lockdep checks in 4.15.
>
> Anyway I think this is an issue with the ww-mutex tests, not my patch
> (none of the code I touched is anywhere in the backtraces), adding
> relevant people.
> -Daniel
>
>
> On Sat, Dec 16, 2017 at 11:42 AM, kernel test robot
> <fengguang.wu@...el.com> wrote:
>> Greetings,
>>
>> 0day kernel testing robot got the below dmesg and the first bad commit is
>>
>> https://github.com/0day-ci/linux/commits/Daniel-Vetter/drm-rework-delayed-connector-cleanup-in-connector_iter/20171216-120456
>>
>> commit 995d11c4c0f1aa99d0f97fb747a4e0d04121cde2
>> Author: Daniel Vetter <daniel.vetter@...ll.ch>
>> AuthorDate: Wed Dec 13 11:45:53 2017 +0100
>> Commit: 0day robot <fengguang.wu@...el.com>
>> CommitDate: Sat Dec 16 12:04:58 2017 +0800
>>
>> drm: rework delayed connector cleanup in connector_iter
>>
>> PROBE_DEFER also uses system_wq to reprobe drivers, which means when
>> that again fails, and we try to flush the overall system_wq (to get
>> all the delayed connectore cleanup work_struct completed), we
>> deadlock.
>>
>> Fix this by using just a single cleanup work, so that we can only
>> flush that one and don't block on anything else. That means a free
>> list plus locking, a standard pattern.
>>
>> Fixes: a703c55004e1 ("drm: safely free connectors from connector_iter")
>> Fixes: 613051dac40d ("drm: locking&new iterators for connector_list")
>> Cc: Ben Widawsky <ben@...dawsk.net>
>> Cc: Dave Airlie <airlied@...il.com>
>> Cc: Chris Wilson <chris@...is-wilson.co.uk>
>> Cc: Sean Paul <seanpaul@...omium.org>
>> Cc: <stable@...r.kernel.org> # v4.11+: 613051dac40d ("drm: locking&new iterators for connector_list"
>> Cc: <stable@...r.kernel.org> # v4.11+
>> Cc: Daniel Vetter <daniel.vetter@...el.com>
>> Cc: Jani Nikula <jani.nikula@...ux.intel.com>
>> Cc: Gustavo Padovan <gustavo@...ovan.org>
>> Cc: David Airlie <airlied@...ux.ie>
>> Cc: Javier Martinez Canillas <javier@...hile0.org>
>> Cc: Shuah Khan <shuahkh@....samsung.com>
>> Cc: Guillaume Tucker <guillaume.tucker@...labora.com>
>> Cc: Mark Brown <broonie@...nel.org>
>> Cc: Kevin Hilman <khilman@...libre.com>
>> Cc: Matt Hart <matthew.hart@...aro.org>
>> Cc: Thierry Escande <thierry.escande@...labora.co.uk>
>> Cc: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> Cc: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>>
>> 50c4c4e268 Linux 4.15-rc3
>> 995d11c4c0 drm: rework delayed connector cleanup in connector_iter
>> +-------------------------------------------------------+-----------+------------+
>> | | v4.15-rc3 | 995d11c4c0 |
>> +-------------------------------------------------------+-----------+------------+
>> | boot_successes | 1 | 0 |
>> | boot_failures | 82 | 15 |
>> | WARNING:possible_circular_locking_dependency_detected | 82 | 15 |
>> | kernel_BUG_at_lib/list_debug.c | 0 | 15 |
>> | invalid_opcode:#[##] | 0 | 15 |
>> | RIP:__list_add_valid | 0 | 15 |
>> | Kernel_panic-not_syncing:Fatal_exception | 0 | 15 |
>> +-------------------------------------------------------+-----------+------------+
>>
>> [ 3.252870] CPU feature 'AVX registers' is not supported.
>> [ 3.261404] AVX2 or AES-NI instructions are not detected.
>> [ 3.262708] AVX2 instructions are not detected.
>> [ 3.770347]
>> [ 3.773471] ======================================================
>> [ 3.773471] WARNING: possible circular locking dependency detected
>> [ 3.773471] 4.15.0-rc3-00001-g995d11c #1 Not tainted
>> [ 3.773471] ------------------------------------------------------
>> [ 3.773471] swapper/0/1 is trying to acquire lock:
>> [ 3.773471] (ww_class_mutex){+.+.}, at: [<00000000134bc923>] test_abba+0x120/0x21e
>> [ 3.773471]
>> [ 3.773471] but now in release context of a crosslock acquired at the following:
>> [ 3.773471] ((completion)&abba.a_ready){+.+.}, at: [<00000000ea3fc8c8>] test_abba_work+0x43/0xab
>> [ 3.773471]
>> [ 3.773471] which lock already depends on the new lock.
>> [ 3.773471]
>> [ 3.773471] the existing dependency chain (in reverse order) is:
>> [ 3.773471]
>> [ 3.773471] -> #1 ((completion)&abba.a_ready){+.+.}:
>> [ 3.773471] __wait_for_common+0x55/0x1fe
>> [ 3.773471] test_abba_work+0x43/0xab
>> [ 3.773471] process_one_work+0x1d4/0x310
>> [ 3.773471] worker_thread+0x1aa/0x25d
>> [ 3.773471] kthread+0x120/0x128
>> [ 3.773471] ret_from_fork+0x24/0x30
>> [ 3.773471]
>> [ 3.773471] -> #0 (ww_class_mutex){+.+.}:
>> [ 3.773471] test_abba+0x120/0x21e
>> [ 3.773471] test_ww_mutex_init+0x88/0x2fd
>> [ 3.773471] do_one_initcall+0x94/0x149
>> [ 3.773471] kernel_init_freeable+0x12a/0x1a6
>> [ 3.773471] kernel_init+0x5/0xe1
>> [ 3.773471]
>> [ 3.773471] other info that might help us debug this:
>> [ 3.773471]
>> [ 3.773471] Possible unsafe locking scenario by crosslock:
>> [ 3.773471]
>> [ 3.773471] CPU0 CPU1
>> [ 3.773471] ---- ----
>> [ 3.773471] lock(ww_class_mutex);
>> [ 3.773471] lock((completion)&abba.a_ready);
>> [ 3.773471] lock(ww_class_mutex);
>> [ 3.773471] unlock((completion)&abba.a_ready);
>> [ 3.773471]
>> [ 3.773471] *** DEADLOCK ***
>> [ 3.773471]
>> [ 3.773471] 3 locks held by swapper/0/1:
>> [ 3.773471] #0: (ww_class_acquire){+.+.}, at: [<00000000f90b2f9f>] test_abba+0x115/0x21e
>> [ 3.773471] #1: (ww_class_mutex){+.+.}, at: [<00000000134bc923>] test_abba+0x120/0x21e
>> [ 3.773471] #2: (&x->wait#7){....}, at: [<0000000092c10ea9>] complete+0x13/0x4b
>> [ 3.773471]
>> [ 3.773471] stack backtrace:
>> [ 3.773471] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.15.0-rc3-00001-g995d11c #1
>> [ 3.773471] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>> [ 3.773471] Call Trace:
>> [ 3.773471] dump_stack+0x79/0xab
>> [ 3.773471] print_circular_bug+0x2a1/0x2af
>> [ 3.773471] check_prev_add+0x88/0x229
>> [ 3.773471] ? __lockdep_init_map+0x1aa/0x1aa
>> [ 3.773471] ? __lock_acquire+0xd7c/0xe2c
>> [ 3.773471] ? _raw_spin_unlock_irq+0x29/0x32
>> [ 3.773471] ? lock_commit_crosslock+0x32e/0x3af
>> [ 3.773471] lock_commit_crosslock+0x32e/0x3af
>> [ 3.773471] complete+0x1f/0x4b
>> [ 3.773471] test_abba+0x128/0x21e
>> [ 3.773471] ? test_cycle_work+0xa1/0xa1
>> [ 3.773471] ? test_abba_work+0x43/0xab
>> [ 3.773471] ? set_debug_rodata+0xc/0xc
>> [ 3.773471] test_ww_mutex_init+0x88/0x2fd
>> [ 3.773471] ? set_debug_rodata+0xc/0xc
>> [ 3.773471] ? lockdep_proc_init+0x51/0x51
>> [ 3.773471] ? set_debug_rodata+0xc/0xc
>> [ 3.773471] do_one_initcall+0x94/0x149
>> [ 3.773471] ? set_debug_rodata+0xc/0xc
>> [ 3.773471] kernel_init_freeable+0x12a/0x1a6
>> [ 3.773471] ? rest_init+0xba/0xba
>> [ 3.773471] kernel_init+0x5/0xe1
>> [ 3.773471] ret_from_fork+0x24/0x30
>> [ 4.213498] tsc: Refined TSC clocksource calibration: 2593.993 MHz
>> [ 4.214153] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x256411d258c, max_idle_ns: 440795337342 ns
>> [ 9.875268] rcu-torture:--- Start of test: nreaders=1 nfakewriters=4 stat_interval=60 verbose=1 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4 shutdown_secs=0 stall_cpu=0 stall_cpu_holdoff=10 stall_cpu_irqsoff=0 n_barrier_cbs=0 onoff_interval=0 onoff_holdoff=0
>> [ 9.878594] rcu-torture: Creating rcu_torture_writer task
>> [ 9.886729] rcu-torture: Creating rcu_torture_fakewriter task
Looks like a selftest that should throw a warn, but not sure why it returns a kernel warning instead of a simple PASS..
>> # HH:MM RESULT GOOD BAD GOOD_BUT_DIRTY DIRTY_NOT_BAD
>> git bisect start 8174afd657ed57f8ea96940235a2f5a5fec10847 50c4c4e268a2d7a3e58ebb698ac74da0de40ae36 --
>> git bisect bad 26cfe9440f51706d7a9639c79f59372b948637e6 # 15:20 B 0 3 16 0 Merge 'mvebu/for-next' into devel-spot-201712161301
>> git bisect bad 0e185f01383d4fdc5827ccd4d894b754234c5e31 # 15:54 B 0 4 17 0 Merge 'linux-review/Nicolin-Chen/ASoC-fsl_ssi-Clean-up-coding-style-level/20171216-032026' into devel-spot-201712161301
>> git bisect bad c00658c095dd5d0a48ebdedd68de9c8c49ab0633 # 16:19 B 0 5 18 0 Merge 'linux-review/Christian-K-nig/MAINTAINERS-add-separate-entry-for-DRM-TTM/20171216-090756' into devel-spot-201712161301
>> git bisect bad 27c51a58b3376c4b5ea0481ed35a3f8f112e5294 # 16:38 B 0 1 14 0 Merge 'snitzer/dm-4.16-nvme_bio' into devel-spot-201712161301
>> git bisect bad 57a3119eb5ea6842e970be28ee659b7d2aa9d432 # 16:54 B 0 8 21 0 Merge 'linux-review/Daniel-Vetter/drm-rework-delayed-connector-cleanup-in-connector_iter/20171216-120456' into devel-spot-201712161301
>> git bisect good de03d6e01cc2c1cb142daf6cb5ee9f72314c4c8b # 17:15 G 11 0 11 11 0day base guard for 'devel-spot-201712161301'
>> git bisect bad 995d11c4c0f1aa99d0f97fb747a4e0d04121cde2 # 17:27 B 0 4 17 0 drm: rework delayed connector cleanup in connector_iter
>> # first bad commit: [995d11c4c0f1aa99d0f97fb747a4e0d04121cde2] drm: rework delayed connector cleanup in connector_iter
>> git bisect good 50c4c4e268a2d7a3e58ebb698ac74da0de40ae36 # 17:36 G 33 0 32 80 Linux 4.15-rc3
>> # extra tests with debug options
>> git bisect bad 995d11c4c0f1aa99d0f97fb747a4e0d04121cde2 # 17:47 B 0 3 16 0 drm: rework delayed connector cleanup in connector_iter
>> # extra tests on HEAD of linux-devel/devel-spot-201712161301
>> git bisect bad 8174afd657ed57f8ea96940235a2f5a5fec10847 # 17:52 B 0 37 53 0 0day head guard for 'devel-spot-201712161301'
>> # extra tests on tree/branch linux-review/Daniel-Vetter/drm-rework-delayed-connector-cleanup-in-connector_iter/20171216-120456
>> git bisect bad 995d11c4c0f1aa99d0f97fb747a4e0d04121cde2 # 18:09 B 0 15 28 0 drm: rework delayed connector cleanup in connector_iter
>> # extra tests with first bad commit reverted
>> git bisect good 14abeded1e578b748e38967e176ec5c97563c45a # 18:41 G 11 0 11 11 Revert "drm: rework delayed connector cleanup in connector_iter"
>>
>> ---
>> 0-DAY kernel test infrastructure Open Source Technology Center
>> https://lists.01.org/pipermail/lkp Intel Corporation
>
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