linux-kernel - [cgroup/task_lock] include/linux/cgroup.h:705 suspicious rcu_dereference

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Message-ID: <20140301155530.GA11882@localhost>
Date:	Sat, 1 Mar 2014 23:55:30 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [cgroup/task_lock] include/linux/cgroup.h:705 suspicious
 rcu_dereference_check() usage!

Greetings,

I got the below dmesg and the first bad commit is

git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-3.15
commit 0e1d768f1b1873272ec4e8dc1482bb5281855017
Author:     Tejun Heo <tj@...nel.org>
AuthorDate: Tue Feb 25 10:04:03 2014 -0500
Commit:     Tejun Heo <tj@...nel.org>
CommitDate: Tue Feb 25 10:04:03 2014 -0500

    cgroup: drop task_lock() protection around task->cgroups
    
    For optimization, task_lock() is additionally used to protect
    task->cgroups.  The optimization is pretty dubious as either
    css_set_rwsem is grabbed anyway or PF_EXITING already protects
    task->cgroups.  It adds only overhead and confusion at this point.
    Let's drop task_[un]lock() and update comments accordingly.
    
    Signed-off-by: Tejun Heo <tj@...nel.org>
    Acked-by: Li Zefan <lizefan@...wei.com>

+---------------------------------+----+
|                                 |    |
+---------------------------------+----+
| boot_successes                  | 0  |
| boot_failures                   | 19 |
| INFO:suspicious_RCU_usage       | 19 |
| backtrace:sched_setaffinity     | 19 |
| backtrace:SyS_sched_setaffinity | 19 |
+---------------------------------+----+

[    6.669173] mountall (89) used greatest stack depth: 6192 bytes left
[   18.371545] 
[   18.372365] ===============================
[   18.373961] [ INFO: suspicious RCU usage. ]
[   18.375319] 3.14.0-rc4-next-20140228-05738-gb148a42 #1 Not tainted
[   18.377213] -------------------------------
[   18.378541] include/linux/cgroup.h:705 suspicious rcu_dereference_check() usage!
[   18.381461] 
[   18.381461] other info that might help us debug this:
[   18.381461] 
[   18.384337] 
[   18.384337] rcu_scheduler_active = 1, debug_locks = 0
[   18.386486] 2 locks held by trinity-c0/3933:
[   18.387921]  #0:  (callback_mutex){+.+...}, at: [<c1174f22>] cpuset_cpus_allowed+0x2f/0xc1
[   18.391127]  #1:  (&(&p->alloc_lock)->rlock){+.+...}, at: [<c1174f37>] cpuset_cpus_allowed+0x44/0xc1
[   18.394605] 
[   18.394605] stack backtrace:
[   18.396302] CPU: 0 PID: 3933 Comm: trinity-c0 Not tainted 3.14.0-rc4-next-20140228-05738-gb148a42 #1
[   18.399067] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.400836]  00000001 00000001 c748bf38 c1eca7bd c748bf54 c1103fe2 c259fd3c c7f98590
[   18.404411]  c7f98590 c31d5850 c748bf84 c748bf64 c1171471 c7f98590 c7f989c4 c748bf78
[   18.407986]  c1174f4c c7f98590 c748bf84 c748bfa0 c748bf98 c10e3fdc 00000f5d c748bf98
[   18.411635] Call Trace:
[   18.412643]  [<c1eca7bd>] dump_stack+0x40/0x5e
[   18.414239]  [<c1103fe2>] lockdep_rcu_suspicious+0x1c0/0x1d7
[   18.415926]  [<c1171471>] task_cs+0x1e3/0x218
[   18.417502]  [<c1174f4c>] cpuset_cpus_allowed+0x59/0xc1
[   18.419083]  [<c10e3fdc>] sched_setaffinity+0x2c9/0x4c5
[   18.420772]  [<c10da19b>] ? copy_from_user+0x44/0x54
[   18.422306]  [<c10e434e>] SyS_sched_setaffinity+0x176/0x1a5
[   18.424083]  [<c1f106ea>] sysenter_do_call+0x12/0x3c
[   18.441975] rds_remove_bound(): rs c8ad5c00 unbinding from 127.0.0.1:4085
[   18.446612] rds_remove_bound(): rs cde8d100 unbinding from 127.172.176.165:42924
[   18.449784] rds_remove_bound(): rs cde93880 unbinding from 127.0.0.1:46584

git bisect start 0dbed0f2678036188d33c11bc4237026715f1a27 v3.13 --
git bisect good 1ccfe6f982674e4b7bd832b904bafcb3db890252  # 06:57     20+      0  watchdog: dw_wdt: Add dependency on HAS_IOMEM
git bisect good 21f1e2055bd55895d19f41d1b45594e1b7087d79  # 07:05     20+      0  Merge remote-tracking branch 'net/master'
git bisect good 5bc0c24c4dd821c5d6306b30c64cbb90f02a8b07  # 07:16     20+      0  Merge remote-tracking branch 'bluetooth/master'
git bisect good 49cba80449a365a063552f2048b1c715c4a997e0  # 07:25     20+      0  Merge remote-tracking branch 'edac-amd/for-next'
git bisect good 41e35f90e31db0ae1e6a9fae52b73cb6af8909af  # 07:38     20+      0  Merge remote-tracking branch 'staging/staging-next'
git bisect  bad 1c0951895878b4634316d448717119904ee6c53c  # 07:46      0-      2  Merge remote-tracking branch 'gpio/for-next'
git bisect  bad dea48a6cb5c45509a77f5ef3b13fa97d1bb0f389  # 07:51      0-      9  Merge remote-tracking branch 'target-updates/for-next'
git bisect good 91e268c5c1ff5106e5e33627eea6411e00400c81  # 07:59     20+      0  Merge remote-tracking branch 'char-misc/char-misc-next'
git bisect  bad bf90690a616351d514a75eefadeea6cf427b0ce3  # 08:05      0-      7  Merge remote-tracking branch 'cgroup/for-next'
git bisect good 96d365e0b86ee7ec6366c99669687e54c9f145e3  # 08:13     20+      0  cgroup: make css_set_lock a rwsem and rename it to css_set_rwsem
git bisect good 2220f5edf5f452480135b57b345e783ffc5c752d  # 08:19     20+      0  Merge branch 'for-3.15' into for-next
git bisect  bad 952aaa125428fae883670a2c2e40ea8044ca1eaa  # 08:24      0-     13  cgroup: update cgroup_transfer_tasks() to either succeed or fail
git bisect good b3dc094e93905ae9c1bc0815402ad8e5b203d068  # 08:30     20+      0  cgroup: use css_set->mg_tasks to track target tasks during migration
git bisect good 1958d2d53dadbb1c9aaf0b37741f13a60098b243  # 08:35     20+      0  cgroup: split process / task migration into four steps
git bisect  bad 0e1d768f1b1873272ec4e8dc1482bb5281855017  # 08:40      0-     11  cgroup: drop task_lock() protection around task->cgroups
git bisect good eaf797abc53b0ab3f0a02d4ef873a565fcce6daa  # 08:47     20+      0  cgroup: update how a newly forked task gets associated with css_set
# first bad commit: [0e1d768f1b1873272ec4e8dc1482bb5281855017] cgroup: drop task_lock() protection around task->cgroups
git bisect good eaf797abc53b0ab3f0a02d4ef873a565fcce6daa  # 08:50     60+      0  cgroup: update how a newly forked task gets associated with css_set
git bisect  bad b148a42ba7823e34971cd4e5b05a5c74fa3311ed  # 08:50      0-     19  Add linux-next specific files for 20140228
git bisect good 8f6eaa4b28ded2c03943a33d9b23325fd8f20841  # 08:59     60+      3  Revert "cgroup: drop task_lock() protection around task->cgroups"
git bisect good 8427defd087ae6c5eaea9d609dfe7f165568accd  # 09:08     60+      0  MAINTAINERS: add maintainer entry for Armada DRM driver
git bisect  bad b148a42ba7823e34971cd4e5b05a5c74fa3311ed  # 09:08      0-     19  Add linux-next specific files for 20140228

Thanks,
Fengguang

View attachment "dmesg-quantal-cairo-11:20140301061810:i386-randconfig-c5-03010320:3.14.0-rc4-next-20140228-05738-gb148a42:1" of type "text/plain" (45633 bytes)

Download attachment "i386-randconfig-c5-03010320-b148a42ba7823e34971cd4e5b05a5c74fa3311ed-INFO:-suspicious-RCU-usage--52439.log" of type "application/octet-stream" (45702 bytes)

View attachment "config-3.14.0-rc4-next-20140228-05738-gb148a42" of type "text/plain" (95194 bytes)

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