Greeting, FYI, we noticed the following commit (built with gcc-9): commit: 4112549ee56c230415ebc5bbfa15533185ceb2e6 ("[PATCH] sched: Optimize __calc_delta.") url: https://github.com/0day-ci/linux/commits/Josh-Don/sched-Optimize-__calc_delta/20210227-035552 base: https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git c5e6fc08feb2b88dc5dac2f3c817e1c2a4cafda4 in testcase: rcutorture version: with following parameters: runtime: 300s test: cpuhotplug torture_type: rcu test-description: rcutorture is rcutorture kernel module load/unload test. test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +-------------------------------------------------------------------------+------------+------------+ | | c5e6fc08fe | 4112549ee5 | +-------------------------------------------------------------------------+------------+------------+ | INFO:rcu_sched_self-detected_stall_on_CPU | 0 | 18 | | RIP:write_comp_data | 0 | 4 | | RIP:rcu_scale_wait_shutdown[rcuscale] | 0 | 6 | | RIP:___might_sleep | 0 | 8 | | RIP:rcu_scale_reader[rcuscale] | 0 | 18 | | BUG:kernel_hang_in_test_stage | 0 | 20 | | RIP:to_kthread | 0 | 7 | | RIP:__sanitizer_cov_trace_pc | 0 | 8 | | RIP:rcu_all_qs | 0 | 3 | | RIP:check_kcov_mode | 0 | 11 | | RIP:test_bit | 0 | 4 | | WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog_nr[rcutorture] | 0 | 8 | | RIP:rcu_torture_fwd_prog_nr[rcutorture] | 0 | 8 | | WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog_cr[rcutorture] | 0 | 9 | | RIP:rcu_torture_fwd_prog_cr[rcutorture] | 0 | 9 | | RIP:__kasan_check_read | 0 | 6 | | INFO:rcu_sched_detected_stalls_on_CPUs/tasks | 0 | 5 | | RIP:torture_must_stop[torture] | 0 | 2 | | RIP:check_memory_region | 0 | 9 | | RIP:__sanitizer_cov_trace_const_cmp4 | 0 | 1 | | RIP:kthread_should_stop | 0 | 1 | +-------------------------------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot [ 487.587615] ------------[ cut here ]------------ [ 487.588208] WARNING: CPU: 0 PID: 3527 at kernel/rcu/rcutorture.c:1969 rcu_torture_fwd_prog_nr+0x467/0x533 [rcutorture] [ 487.589407] Modules linked in: rcutorture torture [ 487.589953] CPU: 0 PID: 3527 Comm: rcu_torture_fwd Tainted: G W 5.11.0-00053-g4112549ee56c #6 [ 487.591092] RIP: 0010:rcu_torture_fwd_prog_nr+0x467/0x533 [rcutorture] [ 487.591823] Code: 80 3c 02 00 74 05 e8 13 6d 4c e1 ff 53 30 48 8b 74 24 20 48 89 c7 e8 97 d7 ff ff 4d 85 e4 49 89 c0 75 0a 48 83 f8 01 77 04 90 <0f> 0b 90 48 8b 54 24 40 4c 89 e1 48 c7 c6 00 20 02 a0 48 c7 c7 a0 [ 487.593721] RSP: 0018:ffff88812db27d80 EFLAGS: 00010297 [ 487.594328] RAX: 0000000000000000 RBX: ffffffffa0025820 RCX: ffff88814393a8c0 [ 487.595140] RDX: ffff88814393a8c0 RSI: 000000000001480d RDI: 000000000001480d [ 487.595942] RBP: ffff88812db27e60 R08: 0000000000000000 R09: 0000000000000000 [ 487.596741] R10: ffffed10297198b1 R11: ffff88814b8cc587 R12: 0000000000000000 [ 487.597488] R13: dffffc0000000000 R14: ffff88814393a8c0 R15: 0000000000000000 [ 487.598286] FS: 0000000000000000(0000) GS:ffff8881e8800000(0000) knlGS:0000000000000000 [ 487.599203] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 487.599860] CR2: 000055b0091b8f68 CR3: 000000014ce44000 CR4: 00000000000406f0 [ 487.600665] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 487.601458] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 487.602258] Call Trace: [ 487.602560] ? __sanitizer_cov_trace_pc+0x1e/0x43 [ 487.603118] ? tick_nohz_full_enabled+0x8e/0x8e [rcutorture] [ 487.603777] ? __next_timer_interrupt+0x1e2/0x1e2 [ 487.604314] ? rcu_torture_boost_cb+0x3f/0x3f [rcutorture] [ 487.604941] ? __do_set_cpus_allowed+0x1e0/0x1e0 [ 487.605476] ? __kasan_check_write+0x14/0x16 [ 487.605965] rcu_torture_fwd_prog+0x106/0x198 [rcutorture] [ 487.606619] ? rcu_torture_fwd_prog_cr+0x5c4/0x5c4 [rcutorture] [ 487.607325] ? __kasan_check_read+0x11/0x13 [ 487.607765] ? write_comp_data+0x24/0x6f [ 487.608204] ? __sanitizer_cov_trace_pc+0x1e/0x43 [ 487.608738] ? __kthread_parkme+0x101/0x16d [ 487.609226] kthread+0x327/0x33b [ 487.609576] ? _raw_spin_unlock_irq+0x9/0x13 [ 487.610021] ? rcu_torture_fwd_prog_cr+0x5c4/0x5c4 [rcutorture] [ 487.610708] ? kthread_queue_delayed_work+0xcd/0xcd [ 487.611282] ret_from_fork+0x1f/0x30 [ 487.611713] ---[ end trace 2946c7758b8349f5 ]--- To reproduce: # build kernel cd linux cp config-5.11.0-00053-g4112549ee56c .config make HOSTCC=gcc-9 CC=gcc-9 ARCH=x86_64 olddefconfig prepare modules_prepare bzImage git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email Thanks, Oliver Sang