linux-kernel - [cgroup/task_lock] INFO: suspicious RCU usage.

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Date:	Fri, 21 Feb 2014 10:16:22 +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] INFO: suspicious RCU 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 review-migration-update-v2

commit fb47fea7a59cf3d6387c566084a6684b5005af83
Author:     Tejun Heo <tj@...nel.org>
AuthorDate: Thu Feb 13 15:16:35 2014 -0500
Commit:     Tejun Heo <tj@...nel.org>
CommitDate: Thu Feb 13 15:16:35 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>

[main] Setsockopt(1 2b 80d1000 4) on fd 223 [17:2:768]
[   27.030764] 
[   27.031119] ===============================
[   27.031833] [ INFO: suspicious RCU usage. ]
[   27.032536] 3.14.0-rc3-02458-g837caba #2 Not tainted
[   27.033378] -------------------------------
[   27.044237] include/linux/cgroup.h:697 suspicious rcu_dereference_check() usage!
[   27.045795] 
[   27.045795] other info that might help us debug this:
[   27.045795] 
[   27.047114] 
[   27.047114] rcu_scheduler_active = 1, debug_locks = 0
[main] Setsockopt(1 c 80d1000 4) on fd 225 [39:5:0]
[   27.048751] 2 locks held by trinity-c0/4479:
[   27.049478]  #0:  (callback_mutex){+.+...}, at: [<81118395>] cpuset_cpus_allowed+0x1e/0x123
[   27.051132]  #1:  (&(&p->alloc_lock)->rlock){+.+...}, at: [<8111839c>] cpuset_cpus_allowed+0x25/0x123
[   27.052788] 
[   27.052788] stack backtrace:
[   27.053528] CPU: 0 PID: 4479 Comm: trinity-c0 Not tainted 3.14.0-rc3-02458-g837caba #2
[   27.064971]  00000000 00000000
 919eff28 81877cc3[main] Setsockopt(1 7 80d1000 4) on fd 226 [1:5:1]

git bisect start 837caba6587ab563ef3779429ddc9f49adb6b6fc 6d0abeca3242a88cab8232e4acd7e2bf088f3bc2 --
git bisect good a2769d08037fdbb3533d916a65e64d55e027e99c  # 06:00     20+      0  Merge 'sparc/master' into devel-hourly-2014022015
git bisect good 1b2a1643a39d52dfd8cea79be9202bfe00852166  # 06:07     20+      1  Merge 'arm-tegra/for-next' into devel-hourly-2014022015
git bisect good 3e8c6ac2fc26d1976164ef0ed588ddf319ea1ae4  # 06:14     20+      5  Merge 'shawnguo/imx6/dt' into devel-hourly-2014022015
git bisect good c8a798fbd56e7dec9cea66a55c9644d1cee51cce  # 06:19     20+      2  Merge 'nmenon/push/voltdm-notifier-v1' into devel-hourly-2014022015
git bisect  bad d753bad21612f2e1ee7e7fa16753aac483f8036f  # 06:25      0-      4  Merge 'cgroup/review-migration-update-v2' into devel-hourly-2014022015
git bisect good 80b13586997d8e584caa772bd99e2a3e55ac6abe  # 06:35     20+      3  cgroup: relocate cgroup_rm_cftypes()
git bisect good 889ed9ceaa97bb02bf5d7349e24639f7fc5f4fa0  # 06:49     20+      2  cgroup: remove css_scan_tasks()
git bisect good 49ef68ad82efeb60f283ef56527ab8969c7e927b  # 07:05     20+      3  cgroup: update cgroup_enable_task_cg_lists() to grab siglock
git bisect good fb6efb01d880e9dcbd19861abd28f55bf061116d  # 07:20     20+      2  cgroup: split process / task migration into four steps
git bisect  bad fb47fea7a59cf3d6387c566084a6684b5005af83  # 07:23      0-     15  cgroup: drop task_lock() protection around task->cgroups
git bisect good d536dafdfb3fe88b2c9e35284ca62d4739589f87  # 07:37     20+      2  cgroup: update how a newly forked task gets associated with css_set
# first bad commit: [fb47fea7a59cf3d6387c566084a6684b5005af83] cgroup: drop task_lock() protection around task->cgroups
git bisect good d536dafdfb3fe88b2c9e35284ca62d4739589f87  # 07:48     60+     16  cgroup: update how a newly forked task gets associated with css_set
git bisect  bad 837caba6587ab563ef3779429ddc9f49adb6b6fc  # 07:49      0-     19  0day head guard for 'devel-hourly-2014022015'
git bisect good 373f7d6eec9fc4ac34f1cca58430d038e0cab88a  # 08:02     60+     11  Revert "cgroup: drop task_lock() protection around task->cgroups"
git bisect good d158fc7f36a25e19791d25a55da5623399a2644f  # 08:16     60+      5  Merge tag 'pci-v3.14-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
git bisect good 12f1d94f0c8b256c04cb9b6b5dd989c32e44f11b  # 08:32     60+     17  Add linux-next specific files for 20140220

Thanks,
Fengguang

View attachment "dmesg-yocto-bens-4:20140220161732:i386-randconfig-c5-02201550:3.14.0-rc3-02458-g837caba:2" of type "text/plain" (122776 bytes)

Download attachment "i386-randconfig-c5-02201550-837caba6587ab563ef3779429ddc9f49adb6b6fc-SyS_sched_setaffinity+-x-23380.log" of type "application/octet-stream" (23947 bytes)

View attachment "config-3.14.0-rc3-02458-g837caba" of type "text/plain" (77589 bytes)