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 AuthorDate: Tue Feb 25 10:04:03 2014 -0500 Commit: Tejun Heo 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 Acked-by: Li Zefan +---------------------------------+----+ | | | +---------------------------------+----+ | 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: [] cpuset_cpus_allowed+0x2f/0xc1 [ 18.391127] #1: (&(&p->alloc_lock)->rlock){+.+...}, at: [] 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] [] dump_stack+0x40/0x5e [ 18.414239] [] lockdep_rcu_suspicious+0x1c0/0x1d7 [ 18.415926] [] task_cs+0x1e3/0x218 [ 18.417502] [] cpuset_cpus_allowed+0x59/0xc1 [ 18.419083] [] sched_setaffinity+0x2c9/0x4c5 [ 18.420772] [] ? copy_from_user+0x44/0x54 [ 18.422306] [] SyS_sched_setaffinity+0x176/0x1a5 [ 18.424083] [] 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