Hi Peter, FYI, this commit shifts the warning from switched_from_fair() to can_migrate_task(). Attached are the dmesg files after/before patch. https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/debug commit d984e601d4db9189f55d79fb8946fc38a334d522 Author: Peter Zijlstra <peterz(a)infradead.org&gt; AuthorDate: Mon Oct 3 16:28:37 2016 +0200 Commit: Peter Zijlstra <peterz(a)infradead.org&gt; CommitDate: Fri Dec 16 21:24:39 2016 +0100 sched: Add missing update_rq_clock() in detach_task_cfs_rq() Instead of adding the update_rq_clock() all the way at the bottom of the callstack, add one at the top, this to aid later effort to minimize update_rq_lock() calls. 4WARNING: CPU: 0 PID: 1 at ../kernel/sched/sched.h:797 detach_task_cfs_rq+0x6fe/0x930 rq->clock_update_flags < RQCF_ACT_SKIPdModules linked in: dCPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-00637-g67223e2-dirty #553 dHardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013 ffffc900000cbc00 ffffffff816152c5 ffffc900000cbc50 0000000000000000 ffffc900000cbc40 ffffffff810d5bab 0000031d00017b00 ffff88042f817b68 ffff88042dbb0000 ffff88042f817b00 ffff88042dbb0000 ffffffff81c18900 Call Trace: [<ffffffff816152c5>] dump_stack+0x67/0x92 [<ffffffff810d5bab>] __warn+0xcb/0xf0 [<ffffffff810d5c1f>] warn_slowpath_fmt+0x4f/0x60 [<ffffffff8110efae>] detach_task_cfs_rq+0x6fe/0x930 [<ffffffff8110f1f1>] switched_from_fair+0x11/0x20 [<ffffffff810fde77>] __sched_setscheduler+0x2a7/0xb40 [<ffffffff810fe779>] _sched_setscheduler+0x69/0x70 [<ffffffff810ff243>] sched_set_stop_task+0x53/0x90 [<ffffffff81173703>] cpu_stop_create+0x23/0x30 [<ffffffff810f90c0>] __smpboot_create_thread.part.2+0xb0/0x100 [<ffffffff810f91ef>] smpboot_register_percpu_thread_cpumask+0xdf/0x140 [<ffffffff823c24e7>] ? pid_namespaces_init+0x40/0x40 [<ffffffff823c254b>] cpu_stop_init+0x64/0x9b [<ffffffff8100040d>] do_one_initcall+0x3d/0x150 [<ffffffff8107763d>] ? print_cpu_info+0x7d/0xe0 [<ffffffff823a0001>] kernel_init_freeable+0xcc/0x207 [<ffffffff81a7d8d0>] ? rest_init+0x90/0x90 [<ffffffff81a7d8de>] kernel_init+0xe/0x100 [<ffffffff81a89bc7>] ret_from_fork+0x27/0x40 4---[ end trace 90bea7c93d2289cb ]--- Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org&gt; +-----------------------------------------------------+------------+------------+------------+ | | 663ffc9df6 | d984e601d4 | 9058057c9a | +-----------------------------------------------------+------------+------------+------------+ | boot_successes | 0 | 0 | 3 | | boot_failures | 96 | 24 | 10 | | WARNING:at_kernel/sched/sched.h:#switched_from_fair | 96 | | | | WARNING:at_kernel/sched/sched.h:#can_migrate_task | 0 | 22 | 9 | | BUG:kernel_reboot-without-warning_in_test_stage | 0 | 2 | 1 | +-----------------------------------------------------+------------+------------+------------+ [ 0.060195] x86/mm: Memory block size: 128MB [ 0.065726] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns [ 0.066020] ------------[ cut here ]------------ [ 0.066648] WARNING: CPU: 1 PID: 15 at kernel/sched/sched.h:804 can_migrate_task+0x18c/0x1b4 [ 0.067000] rq->clock_update_flags < RQCF_ACT_SKIP [ 0.067000] CPU: 1 PID: 15 Comm: kworker/1:0 Not tainted 4.9.0-02688-gd984e60 #1 [ 0.067000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014 [ 0.067000] Call Trace: [ 0.067000] dump_stack+0x85/0xae [ 0.067000] __warn+0xb3/0xce [ 0.067000] warn_slowpath_fmt+0x46/0x4e git bisect start 9058057c9a73c96c4e3eadabb2c3aea119a05d67 69973b830859bc6529a7a0468ba0d80ee5117826 -- git bisect bad 1ad680c707bbefd8bcefb8e187fe9b8e604c95a5 # 15:28 0- 11 Merge 'hwmon/watchdog-next' into devel-spot-201612171041 git bisect good 4d07c2ce6a719b4ed994fd6d540f91ab6be270cb # 15:39 23+ 1 Merge 'l1k/thunderbolt_runpm_v3' into devel-spot-201612171041 git bisect bad c11382c07e74bada7736f9d2dff67b87b358be7d # 15:49 4- 14 Merge 'peterz-queue/sched/debug' into devel-spot-201612171041 git bisect good 93cf7d15a234924b861dcb736d79ee627b6c7776 # 15:59 24+ 23 Merge 'vfs/for-linus' into devel-spot-201612171041 git bisect good 5463133b894f9787320fe0b2dfebe597a867e625 # 16:10 24+ 0 Merge 'linux-review/Ozgur-Karatas/tools-net-bpf_dbg-c-fixed-keyboard-typo/20161217-043841' into devel-spot-201612171041 git bisect good 792886cb3dc81adae8a562ff25a5c27e73a3f62f # 16:22 24+ 12 Merge 'linux-review/Radim-Kr-m/KVM-x86-minor-irqchip-improvements-API-change/20161217-043342' into devel-spot-201612171041 git bisect good bfefa32cc9609ef7b041e60e86d887650ba5ee3c # 16:29 24+ 7 Merge 'tile/master' into devel-spot-201612171041 git bisect good 527bb8647b2c15275495474cb8b5db4533ca3bff # 16:40 24+ 18 sched/fair: Push rq lock pin/unpin into idle_balance() git bisect good 663ffc9df655dc76cfe23541943a3b1222cfd83e # 16:55 24+ 24 sched: Add missing update_rq_clock() in post_init_entity_util_avg(). git bisect bad d984e601d4db9189f55d79fb8946fc38a334d522 # 17:05 0- 13 sched: Add missing update_rq_clock() in detach_task_cfs_rq() # first bad commit: [d984e601d4db9189f55d79fb8946fc38a334d522] sched: Add missing update_rq_clock() in detach_task_cfs_rq() git bisect good 663ffc9df655dc76cfe23541943a3b1222cfd83e # 17:08 72+ 96 sched: Add missing update_rq_clock() in post_init_entity_util_avg(). # extra tests with CONFIG_DEBUG_INFO_REDUCED git bisect bad d984e601d4db9189f55d79fb8946fc38a334d522 # 17:24 0- 12 sched: Add missing update_rq_clock() in detach_task_cfs_rq() # extra tests on HEAD of linux-devel/devel-spot-201612171041 git bisect bad 9058057c9a73c96c4e3eadabb2c3aea119a05d67 # 17:24 0- 10 0day head guard for 'devel-spot-201612171041' # extra tests on tree/branch peterz-queue/sched/debug git bisect good 597f6fc362a11b362050939a734b954fcb285795 # 17:37 68+ 15 sched: Avoid double update_rq_clock() # extra tests with first bad commit reverted git bisect good 61c8ceb96e6f3487fe5547a82002aaba358bae84 # 17:55 69+ 69 Revert "sched: Add missing update_rq_clock() in detach_task_cfs_rq()" # extra tests on tree/branch linus/master git bisect good 59331c215daf600a650e281b6e8ef3e1ed1174c2 # 18:06 69+ 13 Merge tag 'ceph-for-4.10-rc1' of git://github.com/ceph/ceph-client # extra tests on tree/branch linux-next/master git bisect good bf579a3afa46c74b7e89930974ba119d4c76bab2 # 18:17 69+ 27 Add linux-next specific files for 20161216 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/lkp Intel Corporation