bisecting fixing commit since 8a61716ff2ab23eddd1f7a05a075a374e4d0c3d4 building syzkaller on 6a5fcca423a42e14346de8637cc30d79530bf034 testing commit 8a61716ff2ab23eddd1f7a05a075a374e4d0c3d4 with gcc (GCC) 8.1.0 kernel signature: cda351fecd6346d15fba83e820d59ab4d166d2a88c933798e5edab1db3d46180 run #0: crashed: INFO: rcu detected stall in sys_sendfile64 run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in sys_sendfile64 run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in sys_sendfile64 run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in ext4_file_write_iter run #8: crashed: INFO: rcu detected stall in ext4_file_write_iter run #9: crashed: INFO: rcu detected stall in corrupted testing current HEAD 9786cab674574239b04df638f825ee0e7d76a48c testing commit 9786cab674574239b04df638f825ee0e7d76a48c with gcc (GCC) 8.1.0 kernel signature: fe93e8546ca38a21d46063f09f4a55257674d7fa150ee4ee91faa143c7004417 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in corrupted run #4: crashed: INFO: rcu detected stall in sys_sendfile64 run #5: crashed: INFO: rcu detected stall in ext4_file_write_iter run #6: crashed: INFO: rcu detected stall in sys_sendfile64 run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter revisions tested: 2, total time: 21m46.936172395s (build: 11m15.445738135s, test: 9m40.148249168s) the crash still happens on HEAD commit msg: Merge tag 'selinux-pr-20200416' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux crash: INFO: rcu detected stall in ext4_file_write_iter IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready 8021q: adding VLAN 0 to HW filter on device batadv0 sched: RT throttling activated rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (10499 ticks this GP) idle=eda/1/0x4000000000000002 softirq=8499/8508 fqs=1 (t=10500 jiffies g=5685 q=235) rcu: rcu_preempt kthread starved for 10498 jiffies! g5685 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29080 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3372 [inline] __schedule+0x85b/0x1960 kernel/sched/core.c:4088 schedule+0xc3/0x2b0 kernel/sched/core.c:4163 schedule_timeout+0x2bd/0x710 kernel/time/timer.c:1898 rcu_gp_fqs_loop kernel/rcu/tree.c:1674 [inline] rcu_gp_kthread+0x9da/0x1a40 kernel/rcu/tree.c:1836 kthread+0x357/0x420 kernel/kthread.c:268 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 1 CPU: 1 PID: 7799 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x12d/0x187 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.7+0x4b/0x84 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x18b/0x1b7 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:164 [inline] rcu_dump_cpu_stacks+0x1a1/0x1ee kernel/rcu/tree_stall.h:254 print_cpu_stall kernel/rcu/tree_stall.h:475 [inline] check_cpu_stall kernel/rcu/tree_stall.h:549 [inline] rcu_pending kernel/rcu/tree.c:3225 [inline] rcu_sched_clock_irq.cold.87+0x3c7/0xc50 kernel/rcu/tree.c:2296 update_process_times+0x23/0x50 kernel/time/timer.c:1727 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:176 tick_sched_timer+0x43/0x100 kernel/time/tick-sched.c:1320 __run_hrtimer kernel/time/hrtimer.c:1520 [inline] __hrtimer_run_queues+0x52a/0xc10 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 [inline] smp_apic_timer_interrupt+0x16f/0x600 arch/x86/kernel/apic/apic.c:1138 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline] RIP: 0010:lock_acquire+0x291/0x9e0 kernel/locking/lockdep.c:4937 Code: ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 64 06 00 00 48 83 3d ae f3 20 07 00 0f 84 d3 04 00 00 48 8b bd 48 ff ff ff 57 9d <0f> 1f 44 00 00 48 b8 00 00 00 00 00 fc ff df 48 01 c3 c7 03 00 00 RSP: 0018:ffff8880943ff078 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: 1ffff1101287fe13 RCX: 1ffff1101287fdf8 RDX: 1ffffffff10e8e04 RSI: 0000000000000001 RDI: 0000000000000286 RBP: ffff8880943ff140 R08: fffffbfff13db838 R09: fffffbfff13db838 R10: ffffffff89edc1bf R11: fffffbfff13db837 R12: ffff888091b50640 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:353 [inline] ext4_do_update_inode fs/ext4/inode.c:4948 [inline] ext4_mark_iloc_dirty+0x271/0x2f10 fs/ext4/inode.c:5603 ext4_mark_inode_dirty+0x1e3/0x790 fs/ext4/inode.c:5796 ext4_dirty_inode+0xc6/0x100 fs/ext4/inode.c:5827 __mark_inode_dirty+0x493/0xe60 fs/fs-writeback.c:2258 mark_inode_dirty include/linux/fs.h:2189 [inline] generic_write_end+0x176/0x230 fs/buffer.c:2193 ext4_da_write_end+0x171/0xa40 fs/ext4/inode.c:3090 generic_perform_write+0x356/0x4a0 mm/filemap.c:3313 ext4_buffered_write_iter+0x1be/0x3d0 fs/ext4/file.c:270 ext4_file_write_iter+0x1b7/0x13b0 fs/ext4/file.c:642 call_write_iter include/linux/fs.h:1907 [inline] do_iter_readv_writev+0x53c/0xa80 fs/read_write.c:694 do_iter_write+0x12e/0x550 fs/read_write.c:999 vfs_iter_write+0x5b/0xb0 fs/read_write.c:1040 iter_file_splice_write+0x57c/0xb80 fs/splice.c:760 do_splice_from fs/splice.c:863 [inline] direct_splice_actor+0x107/0x1c0 fs/splice.c:1037 splice_direct_to_actor+0x348/0x960 fs/splice.c:992 do_splice_direct+0x158/0x280 fs/splice.c:1080 do_sendfile+0x4a9/0xe30 fs/read_write.c:1521 __do_sys_sendfile64 fs/read_write.c:1576 [inline] __se_sys_sendfile64 fs/read_write.c:1568 [inline] __x64_sys_sendfile64+0x12e/0x1e0 fs/read_write.c:1568 do_syscall_64+0xd0/0x630 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x457f79 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f5601d35c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457f79 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f5601d366d4 R13: 00000000004c4e6e R14: 00000000004d8b98 R15: 00000000ffffffff