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Goncalves" To: kernel test robot Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Peter Zijlstra , Crystal Wood , Wander Lairson Costa , Valentin Schneider , Sebastian Andrzej Siewior , aubrey.li@linux.intel.com, yu.c.chen@intel.com Subject: Re: [linus:master] [sched] 8671bad873: INFO:task_blocked_for_more_than#seconds Message-ID: References: <202509051010.e06823ab-lkp@intel.com> Precedence: bulk X-Mailing-List: oe-lkp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202509051010.e06823ab-lkp@intel.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Fri, Sep 05, 2025 at 10:49:35AM +0800, kernel test robot wrote: > > > Hello, > > kernel test robot noticed "INFO:task_blocked_for_more_than#seconds" on: > > commit: 8671bad873ebeb082afcf7b4501395c374da6023 ("sched: Do not call __put_task_struct() on rt if pi_blocked_on is set") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > [test failed on linus/master 08b06c30a44555a8b1d14950e4462a52bfa0758b] > [test failed on linux-next/master 5d50cf9f7cf20a17ac469c20a2e07c29c1f6aab7] > > in testcase: rcutorture > version: > with following parameters: > > runtime: 300s > test: cpuhotplug > torture_type: tasks-rude I ran tests with the boxes I had at hand, x86_64 and arm64, and was unable to reproduce the problem. Tomorrow, when I am back from a holiday,, I will try to reproduce the problem with x86 (32 bits) VMs and x86 baremetal as it seems to be the case on the report. In any case, I sent a follow-up patch that isolated those changes to kernels with PREEMPT_RT enabled, as initially intended. That should solve this case (if really caused by the commit in question). The patch I mentioned is: [RESEND PATCH] sched: restore the behavior of put_task_struct() for non-rt https://lore.kernel.org/all/aKxqGLNOp2sWJwnZ@uudg.org/ Best regards, Luis > > > config: i386-randconfig-017-20250830 > compiler: gcc-12 > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G > > (please refer to attached dmesg/kmsg for entire log/backtrace) > > > the issue happens randomly and we observed various issues in tests by this > commit, while parent keeps clean. > > ========================================================================================= > tbox_group/testcase/rootfs/kconfig/compiler/runtime/test/torture_type: > vm-snb/rcutorture/debian-11.1-i386-20220923.cgz/i386-randconfig-017-20250830/gcc-12/300s/cpuhotplug/tasks-rude > > 7de9d4f946383f48 8671bad873ebeb082afcf7b4501 > ---------------- --------------------------- > fail:runs %reproduction fail:runs > | | | > :200 16% 32:200 dmesg.BUG:kernel_hang_in_boot_stage > :200 0% 1:200 dmesg.BUG:soft_lockup-CPU##stuck_for#s![swapper:#] > :200 1% 2:200 dmesg.BUG:workqueue_lockup-pool > :200 0% 1:200 dmesg.EIP:kthread_affine_preferred > :200 0% 1:200 dmesg.EIP:lock_release > :200 0% 1:200 dmesg.EIP:tick_clock_notify > :200 12% 23:200 dmesg.INFO:task_blocked_for_more_than#seconds > :200 12% 23:200 dmesg.Kernel_panic-not_syncing:hung_task:blocked_tasks > :200 0% 1:200 dmesg.Kernel_panic-not_syncing:softlockup:hung_tasks > :200 0% 1:200 dmesg.WARNING:at_kernel/kthread.c:#kthread_affine_preferred > > > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Reported-by: kernel test robot > | Closes: https://lore.kernel.org/oe-lkp/202509051010.e06823ab-lkp@intel.com > > > [ 994.935251][ T26] INFO: task swapper/0:1 blocked for more than 491 seconds. > [ 994.947414][ T26] Not tainted 6.16.0-rc6-00086-g8671bad873eb #1 > [ 994.951523][ T26] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 994.960576][ T26] task:swapper/0 state:D stack:5016 pid:1 tgid:1 ppid:0 task_flags:0x0140 flags:0x00004000 > [ 994.972581][ T26] Call Trace: > [ 994.998429][ T26] __schedule (kernel/sched/core.c:5354 kernel/sched/core.c:6954) > [ 995.035758][ T26] schedule (kernel/sched/core.c:7037 kernel/sched/core.c:7051) > [ 995.044863][ T26] async_synchronize_cookie_domain (kernel/async.c:317 kernel/async.c:310) > [ 995.050698][ T26] ? do_wait_intr (kernel/sched/wait.c:384) > [ 995.059798][ T26] wait_for_initramfs (init/initramfs.c:778) > [ 995.067798][ T26] populate_rootfs (init/initramfs.c:789) > [ 995.070767][ T26] do_one_initcall (init/main.c:1274) > [ 995.074441][ T26] ? initramfs_async_setup (init/initramfs.c:782) > [ 995.098384][ T26] do_initcalls (init/main.c:1335 init/main.c:1352) > [ 995.136744][ T26] kernel_init_freeable (init/main.c:1588) > [ 995.136744][ T26] ? rest_init (init/main.c:1466) > [ 995.158663][ T26] kernel_init (init/main.c:1476) > [ 995.177750][ T26] ret_from_fork (arch/x86/kernel/process.c:154) > [ 995.178146][ T26] ? rest_init (init/main.c:1466) > [ 995.230129][ T26] ret_from_fork_asm (arch/x86/entry/entry_32.S:737) > [ 995.230129][ T26] entry_INT80_32 (arch/x86/entry/entry_32.S:945) > [ 995.268743][ T26] > [ 995.268743][ T26] Showing all locks held in the system: > [ 995.336987][ T26] 1 lock held by khungtaskd/26: > [ 995.446697][ T26] #0: 830cce10 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks (kernel/locking/lockdep.c:6768 (discriminator 1)) > [ 995.464546][ T26] 4 locks held by kworker/u4:2/29: > [ 995.470758][ T26] 2 locks held by kworker/0:3/38: > [ 995.498593][ T26] > [ 995.599251][ T26] ============================================= > [ 995.599251][ T26] > [ 995.729940][ T26] Kernel panic - not syncing: hung_task: blocked tasks > [ 995.729940][ T26] CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted 6.16.0-rc6-00086-g8671bad873eb #1 PREEMPT(full) > [ 995.729940][ T26] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 995.729940][ T26] Call Trace: > [ 995.729940][ T26] dump_stack_lvl (lib/dump_stack.c:124) > [ 995.729940][ T26] dump_stack (lib/dump_stack.c:130) > [ 995.729940][ T26] panic (kernel/panic.c:382) > [ 995.729940][ T26] check_hung_uninterruptible_tasks (kernel/hung_task.c:311) > [ 995.729940][ T26] watchdog (kernel/hung_task.c:470) > [ 995.729940][ T26] kthread (kernel/kthread.c:464) > [ 995.729940][ T26] ? check_hung_uninterruptible_tasks (kernel/hung_task.c:453) > [ 995.729940][ T26] ? kthread_complete_and_exit (kernel/kthread.c:413) > [ 995.729940][ T26] ret_from_fork (arch/x86/kernel/process.c:154) > [ 995.729940][ T26] ? kthread_complete_and_exit (kernel/kthread.c:413) > [ 995.729940][ T26] ret_from_fork_asm (arch/x86/entry/entry_32.S:737) > [ 995.729940][ T26] entry_INT80_32 (arch/x86/entry/entry_32.S:945) > > > > The kernel config and materials to reproduce are available at: > https://download.01.org/0day-ci/archive/20250905/202509051010.e06823ab-lkp@intel.com > > > > -- > 0-DAY CI Kernel Test Service > https://github.com/intel/lkp-tests/wiki > ---end quoted text---