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 AuthorDate: Thu Feb 13 15:16:35 2014 -0500 Commit: Tejun Heo 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 [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