bisecting fixing commit since f4cc0ed9b2c72687303b035379c5824a02224354
building syzkaller on 7509bf360eba1461ac6059e4cacfbc29c9d2d4c7
testing commit f4cc0ed9b2c72687303b035379c5824a02224354 with gcc (GCC) 8.1.0
kernel signature: fb07a4326455eeaf5525bdbe4dd256a6e50fd0d92c6babd7c3693ffad8adb5f0
run #0: crashed: BUG: workqueue lockup
run #1: crashed: BUG: workqueue lockup
run #2: crashed: BUG: workqueue lockup
run #3: crashed: BUG: workqueue lockup
run #4: crashed: BUG: workqueue lockup
run #5: crashed: BUG: workqueue lockup
run #6: crashed: BUG: workqueue lockup
run #7: crashed: BUG: workqueue lockup
run #8: crashed: BUG: workqueue lockup
run #9: crashed: INFO: rcu detected stall in corrupted
testing current HEAD 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae
testing commit 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae with gcc (GCC) 8.1.0
kernel signature: bd037e5e240e84bf64f48f76b00a53cc7a0636195725b8d15260be4c7c1018fb
run #0: crashed: BUG: workqueue lockup
run #1: crashed: BUG: workqueue lockup
run #2: crashed: BUG: workqueue lockup
run #3: crashed: BUG: workqueue lockup
run #4: crashed: BUG: workqueue lockup
run #5: crashed: BUG: workqueue lockup
run #6: crashed: BUG: workqueue lockup
run #7: crashed: BUG: workqueue lockup
run #8: crashed: BUG: workqueue lockup
run #9: crashed: INFO: rcu detected stall in corrupted
revisions tested: 2, total time: 25m45.229576736s (build: 16m32.099602584s, test: 8m29.358990628s)
the crash still happens on HEAD
commit msg: Linux 4.14.212
crash: INFO: rcu detected stall in corrupted
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-...: (10501 ticks this GP) idle=a2a/140000000000000/0 softirq=8967/8979 fqs=11 
	(detected by 1, t=10503 jiffies, g=219, c=218, q=5)
INFO: rcu_preempt self-detected stall on CPU
Sending NMI from CPU 1 to CPUs 0:
	0-...: (10499 ticks this GP) idle=a2a/140000000000001/0 softirq=8979/8979 fqs=9 
NMI backtrace for cpu 0
CPU: 0 PID: 6468 Comm: syz-executor.1 Not tainted 4.14.212-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8881d71861c0 task.stack: ffff8881dd2c0000
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:2361 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:2381 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:2435 [inline]
RIP: 0010:__lock_acquire+0xd8d/0x4500 kernel/locking/lockdep.c:3491
RSP: 0018:ffff8881f68075f0 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffffffff88868948 RCX: ffff8881d7186a48
RDX: 1ffffffff11d1f3f RSI: ffff8881d7186ae8 RDI: ffff8881d7186b09
RBP: ffff8881f68077c0 R08: ffff8881d7186b08 R09: 00000000000076b7
R10: 00000000000000a0 R11: ffff8881d71861c0 R12: 00000000add3a998
R13: 00000000e348f329 R14: 9b527b33911c9cc1 R15: ffff8881d7186ae8
FS:  00007f9c1f393700(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000758080 CR3: 00000001dd46d006 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x173/0x400 kernel/locking/lockdep.c:3998
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:160
 serial8250_console_write+0x69f/0x860 drivers/tty/serial/8250/8250_port.c:3253
 univ8250_console_write+0x4e/0x70 drivers/tty/serial/8250/8250_core.c:596
 call_console_drivers kernel/printk/printk.c:1725 [inline]
 console_unlock+0x8c2/0xe30 kernel/printk/printk.c:2400
 vprintk_emit+0x1b4/0x4e0 kernel/printk/printk.c:1923
 vprintk_default+0x1a/0x20 kernel/printk/printk.c:1963
 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:401
 printk+0x91/0xab kernel/printk/printk.c:1996
 print_cpu_stall_info+0x3ce/0x850 kernel/rcu/tree_plugin.h:1700
 print_cpu_stall kernel/rcu/tree.c:1531 [inline]
 check_cpu_stall kernel/rcu/tree.c:1610 [inline]
 __rcu_pending kernel/rcu/tree.c:3390 [inline]
 rcu_pending kernel/rcu/tree.c:3452 [inline]
 rcu_check_callbacks.cold.77+0x56/0xcfa kernel/rcu/tree.c:2792
 update_process_times+0x2a/0x60 kernel/time/timer.c:1591
 tick_sched_handle+0x7b/0x140 kernel/time/tick-sched.c:165
 tick_sched_timer+0x34/0xf0 kernel/time/tick-sched.c:1223
 __run_hrtimer kernel/time/hrtimer.c:1223 [inline]
 __hrtimer_run_queues+0x297/0xaf0 kernel/time/hrtimer.c:1287
 hrtimer_interrupt+0x1ae/0x600 kernel/time/hrtimer.c:1321
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
 smp_apic_timer_interrupt+0x11f/0x5d0 arch/x86/kernel/apic/apic.c:1100
 apic_timer_interrupt+0x9a/0xa0 arch/x86/entry/entry_64.S:793
 </IRQ>
RIP: 0010:constant_test_bit arch/x86/include/asm/bitops.h:328 [inline]
RIP: 0010:PageLocked include/linux/page-flags.h:265 [inline]
RIP: 0010:unlock_page+0x6d/0xd0 mm/filemap.c:1129
RSP: 0018:ffff8881dd2c7400 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000000 RBX: ffffea0006e73f00 RCX: 0000000000000000
RDX: 1ffffd4000dce7e0 RSI: ffffffff879908e0 RDI: ffffea0006e73f00
RBP: ffff8881dd2c7410 R08: 0000000000000001 R09: 0000000000000000
R10: ffff8881dd2c72e8 R11: 0000000000000040 R12: ffffea0006e73f00
R13: ffff8881de73fd40 R14: dffffc0000000000 R15: ffff8881e4c86140
 ext4_da_write_begin+0x257/0xb20 fs/ext4/inode.c:3077
 generic_perform_write+0x271/0x450 mm/filemap.c:3055
 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3180
 ext4_file_write_iter+0x27a/0xe40 fs/ext4/file.c:270
 call_write_iter include/linux/fs.h:1778 [inline]
 do_iter_readv_writev+0x460/0x900 fs/read_write.c:675
 do_iter_write+0x12b/0x520 fs/read_write.c:954
 vfs_iter_write+0x5b/0xb0 fs/read_write.c:967
 iter_file_splice_write+0x540/0xc20 fs/splice.c:749
 do_splice_from fs/splice.c:851 [inline]
 direct_splice_actor+0x104/0x1c0 fs/splice.c:1018
 splice_direct_to_actor+0x27c/0x750 fs/splice.c:973
 do_splice_direct+0x144/0x250 fs/splice.c:1061
 do_sendfile+0x463/0xd00 fs/read_write.c:1441
 SYSC_sendfile64 fs/read_write.c:1496 [inline]
 SyS_sendfile64+0x97/0x110 fs/read_write.c:1488
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x459599
RSP: 002b:00007f9c1f392c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459599
RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f9c1f3936d4
R13: 00000000004c6b70 R14: 00000000004dbde8 R15: 00000000ffffffff
Code: 44 e5 88 48 89 c2 48 89 44 24 60 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 47 2a 00 00 4a 8b 1c cd 40 44 e5 88 <48> 85 db 0f 84 ca 00 00 00 48 83 fb 08 0f 84 c0 00 00 00 48 8d 
rcu_sched kthread starved for 10475 jiffies! g219 c218 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
	
rcu_sched       R
 (t=10500 jiffies g=1148 c=1147 q=448)
rcu_preempt kthread starved for 10475 jiffies! g1148 c1147 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
  running task    
rcu_preempt     R
29536     9      2 0x80000000
  running task    
Call Trace:
29720     8      2 0x80000000
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x780/0x1d20 kernel/sched/core.c:3384
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x780/0x1d20 kernel/sched/core.c:3384
 schedule+0x7f/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x40c/0xcc0 kernel/time/timer.c:1747
 schedule+0x7f/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x40c/0xcc0 kernel/time/timer.c:1747
 rcu_gp_kthread+0xbbf/0x1e00 kernel/rcu/tree.c:2255
 rcu_gp_kthread+0xbbf/0x1e00 kernel/rcu/tree.c:2255
 kthread+0x338/0x400 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
 kthread+0x338/0x400 kernel/kthread.c:232
NMI backtrace for cpu 0
CPU: 0 PID: 6468 Comm: syz-executor.1 Not tainted 4.14.212-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0xe6/0x11a lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:158 [inline]
 rcu_dump_cpu_stacks+0x172/0x1bf kernel/rcu/tree.c:1396
 print_cpu_stall kernel/rcu/tree.c:1542 [inline]
 check_cpu_stall kernel/rcu/tree.c:1610 [inline]
 __rcu_pending kernel/rcu/tree.c:3390 [inline]
 rcu_pending kernel/rcu/tree.c:3452 [inline]
 rcu_check_callbacks.cold.77+0x415/0xcfa kernel/rcu/tree.c:2792
 update_process_times+0x2a/0x60 kernel/time/timer.c:1591
 tick_sched_handle+0x7b/0x140 kernel/time/tick-sched.c:165
 tick_sched_timer+0x34/0xf0 kernel/time/tick-sched.c:1223
 __run_hrtimer kernel/time/hrtimer.c:1223 [inline]
 __hrtimer_run_queues+0x297/0xaf0 kernel/time/hrtimer.c:1287
 hrtimer_interrupt+0x1ae/0x600 kernel/time/hrtimer.c:1321
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
 smp_apic_timer_interrupt+0x11f/0x5d0 arch/x86/kernel/apic/apic.c:1100
 apic_timer_interrupt+0x9a/0xa0 arch/x86/entry/entry_64.S:793
 </IRQ>
RIP: 0010:constant_test_bit arch/x86/include/asm/bitops.h:328 [inline]
RIP: 0010:PageLocked include/linux/page-flags.h:265 [inline]
RIP: 0010:unlock_page+0x6d/0xd0 mm/filemap.c:1129
RSP: 0018:ffff8881dd2c7400 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000000 RBX: ffffea0006e73f00 RCX: 0000000000000000
RDX: 1ffffd4000dce7e0 RSI: ffffffff879908e0 RDI: ffffea0006e73f00
RBP: ffff8881dd2c7410 R08: 0000000000000001 R09: 0000000000000000
R10: ffff8881dd2c72e8 R11: 0000000000000040 R12: ffffea0006e73f00
R13: ffff8881de73fd40 R14: dffffc0000000000 R15: ffff8881e4c86140
 ext4_da_write_begin+0x257/0xb20 fs/ext4/inode.c:3077
 generic_perform_write+0x271/0x450 mm/filemap.c:3055
 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3180
 ext4_file_write_iter+0x27a/0xe40 fs/ext4/file.c:270
 call_write_iter include/linux/fs.h:1778 [inline]
 do_iter_readv_writev+0x460/0x900 fs/read_write.c:675
 do_iter_write+0x12b/0x520 fs/read_write.c:954
 vfs_iter_write+0x5b/0xb0 fs/read_write.c:967
 iter_file_splice_write+0x540/0xc20 fs/splice.c:749
 do_splice_from fs/splice.c:851 [inline]
 direct_splice_actor+0x104/0x1c0 fs/splice.c:1018
 splice_direct_to_actor+0x27c/0x750 fs/splice.c:973
 do_splice_direct+0x144/0x250 fs/splice.c:1061
 do_sendfile+0x463/0xd00 fs/read_write.c:1441
 SYSC_sendfile64 fs/read_write.c:1496 [inline]
 SyS_sendfile64+0x97/0x110 fs/read_write.c:1488
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x459599
RSP: 002b:00007f9c1f392c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459599
RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f9c1f3936d4
R13: 00000000004c6b70 R14: 00000000004dbde8 R15: 00000000ffffffff