On 4/18/20 10:06 PM, Hillf Danton wrote: > > Sat, 18 Apr 2020 11:59:13 -0700 >> >> syzbot found the following crash on: >> >> HEAD commit: 8f3d9f35 Linux 5.7-rc1 >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=115720c3e00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=5d351a1019ed81a2 >> dashboard link: https://syzkaller.appspot.com/bug?extid=66243bb7126c410cefe6 >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> >> Unfortunately, I don't have any reproducer for this crash yet. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+66243bb7126c410cefe6@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> rcu: INFO: rcu_preempt self-detected stall on CPU >> rcu: 0-....: (10500 ticks this GP) idle=57e/1/0x4000000000000002 softirq=44329/44329 fqs=5245 >> (t=10502 jiffies g=79401 q=2096) >> NMI backtrace for cpu 0 >> CPU: 0 PID: 23184 Comm: syz-executor.5 Not tainted 5.7.0-rc1-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:77 [inline] >> dump_stack+0x188/0x20d lib/dump_stack.c:118 >> nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 >> nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 >> trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] >> rcu_dump_cpu_stacks+0x19b/0x1e5 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+0x55d/0xcfa kernel/rcu/tree.c:2296 >> update_process_times+0x25/0x60 kernel/time/timer.c:1727 >> tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176 >> tick_sched_timer+0x4e/0x140 kernel/time/tick-sched.c:1320 >> __run_hrtimer kernel/time/hrtimer.c:1520 [inline] >> __hrtimer_run_queues+0x5ca/0xed0 kernel/time/hrtimer.c:1584 >> hrtimer_interrupt+0x312/0x770 kernel/time/hrtimer.c:1646 >> local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 [inline] >> smp_apic_timer_interrupt+0x15b/0x600 arch/x86/kernel/apic/apic.c:1138 >> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 >> </IRQ> >> RIP: 0010:io_ring_ctx_wait_and_kill+0x98/0x5a0 fs/io_uring.c:7301 >> Code: 01 00 00 4d 89 f4 48 b8 00 00 00 00 00 fc ff df 4c 89 ed 49 c1 ec 03 48 c1 ed 03 49 01 c4 48 01 c5 eb 1c e8 3a ea 9d ff f3 90 <41> 80 3c 24 00 0f 85 53 04 00 00 48 83 bb 10 01 00 00 00 74 21 e8 >> RSP: 0018:ffffc9000897fdf0 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 >> RAX: ffff888024082080 RBX: ffff88808df8e000 RCX: 1ffff9200112ffab >> RDX: 0000000000000000 RSI: ffffffff81d549c6 RDI: ffff88808df8e300 >> RBP: ffffed1011bf1c2c R08: 0000000000000001 R09: ffffed1011bf1c61 >> R10: ffff88808df8e307 R11: ffffed1011bf1c60 R12: ffffed1011bf1c22 >> R13: ffff88808df8e160 R14: ffff88808df8e110 R15: ffffffff81d54ed0 >> io_uring_release+0x3e/0x50 fs/io_uring.c:7324 >> __fput+0x33e/0x880 fs/file_table.c:280 >> task_work_run+0xf4/0x1b0 kernel/task_work.c:123 >> tracehook_notify_resume include/linux/tracehook.h:188 [inline] >> exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:165 >> prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:279 [inline] >> do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305 >> entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > Make io ring ctx's percpu_ref balanced. > > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -5904,6 +5904,7 @@ static int io_submit_sqes(struct io_ring > fail_req: > io_cqring_add_event(req, err); > io_double_put_req(req); > + --submitted; > break; > } Not sure this is right, need to look closer. But if we post a completion event, the event has been consumed and should be accounted as such. -- Jens Axboe
