bisecting fixing commit since 4b6c093e21d36bede0fd88fd0aeb3b03647260e4
building syzkaller on 424dd8e7b52828cad44ce653a5d4ac30670f5e2c
testing commit 4b6c093e21d36bede0fd88fd0aeb3b03647260e4 with gcc (GCC) 8.1.0
kernel signature: 44bd481985122b06b2bf107fffaa206f443b14fde97024998625d53e4c0cd31b
run #0: crashed: BUG: workqueue lockup
run #1: crashed: BUG: workqueue lockup
run #2: crashed: BUG: workqueue lockup
run #3: crashed: BUG: soft lockup in smp_call_function
run #4: crashed: no output from test machine
run #5: crashed: no output from test machine
run #6: crashed: no output from test machine
run #7: crashed: no output from test machine
run #8: crashed: no output from test machine
run #9: crashed: no output from test machine
testing current HEAD d64c6f96ba86bd8b97ed8d6762a8c8cc1770d214
testing commit d64c6f96ba86bd8b97ed8d6762a8c8cc1770d214 with gcc (GCC) 8.1.0
kernel signature: 14910c16c1ce846286f9069a618a59b4f618bf3ab9dcbadc794f4ff65878c179
run #0: crashed: BUG: workqueue lockup
run #1: crashed: INFO: rcu detected stall in do_idle
run #2: crashed: INFO: rcu detected stall in smp_call_function
run #3: crashed: INFO: rcu detected stall in do_idle
run #4: crashed: INFO: rcu detected stall in do_idle
run #5: crashed: INFO: rcu detected stall in do_idle
run #6: crashed: INFO: rcu detected stall in do_idle
run #7: crashed: INFO: rcu detected stall in do_idle
run #8: crashed: INFO: rcu detected stall in do_idle
run #9: crashed: INFO: rcu detected stall in do_idle
revisions tested: 2, total time: 25m2.160146304s (build: 9m23.901111249s, test: 14m58.267737301s)
the crash still happens on HEAD
commit msg: Merge tag 'net-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
crash: INFO: rcu detected stall in do_idle
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (1 ticks this GP) idle=ba2/0/0x1 softirq=9577/9577 fqs=0 
	(t=25228 jiffies g=3997 q=866)
rcu: rcu_preempt kthread starved for 25228 jiffies! g3997 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:I stack:14328 pid:   10 ppid:     2 flags:0x00004000
Call Trace:
 context_switch kernel/sched/core.c:4327 [inline]
 __schedule+0x420/0x8c0 kernel/sched/core.c:5078
 schedule+0x38/0xe0 kernel/sched/core.c:5157
 schedule_timeout+0x1be/0x2e0 kernel/time/timer.c:1878
 rcu_gp_fqs_loop kernel/rcu/tree.c:1940 [inline]
 rcu_gp_kthread+0x758/0xcc0 kernel/rcu/tree.c:2113
 kthread+0x145/0x170 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0xa3/0xc8 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold.8+0x53/0x6d lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0xd5/0xf0 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0xa2/0xce kernel/rcu/tree_stall.h:337
 print_cpu_stall kernel/rcu/tree_stall.h:569 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:643 [inline]
 rcu_pending kernel/rcu/tree.c:3751 [inline]
 rcu_sched_clock_irq.cold.97+0x61/0x5eb kernel/rcu/tree.c:2580
 update_process_times+0x8e/0xc0 kernel/time/timer.c:1782
 tick_sched_handle.isra.21+0x1a/0x50 kernel/time/tick-sched.c:226
 tick_sched_timer+0x6a/0x80 kernel/time/tick-sched.c:1376
 __run_hrtimer kernel/time/hrtimer.c:1519 [inline]
 __hrtimer_run_queues+0x1e3/0x4f0 kernel/time/hrtimer.c:1583
 hrtimer_interrupt+0xf9/0x210 kernel/time/hrtimer.c:1645
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline]
 __sysvec_apic_timer_interrupt+0x8e/0x290 arch/x86/kernel/apic/apic.c:1102
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0xcc/0xf0 arch/x86/kernel/apic/apic.c:1096
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:628
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 5b c3 65 48 8b 04 25 c0 7e 01 00 f0 80 48 02 20 48 8b 00 a8 08 75 c3 e9 7c ff ff ff e9 07 00 00 00 0f 00 2d 7c ba 4f 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 6c ba 4f 00 f4 c3 cc cc e8 2b 08 ff
RSP: 0018:ffffffff84403e38 EFLAGS: 00000286
RAX: 000000000002b04f RBX: ffff888103f75000 RCX: 00000000ffffffff
RDX: 0000000000000000 RSI: ffffffff83f3d753 RDI: ffffffff83f7ada6
RBP: ffffffff8472b3e0 R08: 0000000000000001 R09: 0000000000000001
R10: ffff888237c2c684 R11: ffff888237c2c664 R12: 0000000000000001
R13: ffff888100d56c64 R14: 0000000000000001 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline]
 acpi_safe_halt drivers/acpi/processor_idle.c:110 [inline]
 acpi_idle_do_entry+0x50/0x90 drivers/acpi/processor_idle.c:516
 acpi_idle_enter+0xa0/0xf0 drivers/acpi/processor_idle.c:647
 cpuidle_enter_state+0x94/0x520 drivers/cpuidle/cpuidle.c:237
 cpuidle_enter+0x24/0x40 drivers/cpuidle/cpuidle.c:351
 call_cpuidle kernel/sched/idle.c:158 [inline]
 cpuidle_idle_call kernel/sched/idle.c:239 [inline]
 do_idle+0x2dc/0x350 kernel/sched/idle.c:299
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:396
 start_kernel+0x4f2/0x511 init/main.c:1061
 secondary_startup_64_no_verify+0xb0/0xbb