Re: [Qemu-block] [Qemu-devel] [PATCH 0/4] Tweaks around virtio-blk start/stop

[Christian Borntraeger]

On 03/17/2016 04:02 PM, Paolo Bonzini wrote:
> 
> 
> On 17/03/2016 13:39, Christian Borntraeger wrote:
>> As an interesting side note, I updated my system from F20 to F23 some days 
>> ago
>> (after the initial report). While To Bo is still on a F20 system. I was not 
>> able
>> to reproduce the original crash on f23. but going back to F20 made this
>> problem re-appear.
>>  
>>   Stack trace of thread 26429:
>>                 #0  0x00000000802008aa tracked_request_begin 
>> (qemu-system-s390x)
>>                 #1  0x0000000080203f3c bdrv_co_do_preadv (qemu-system-s390x)
>>                 #2  0x000000008020567c bdrv_co_do_readv (qemu-system-s390x)
>>                 #3  0x000000008025d0f4 coroutine_trampoline 
>> (qemu-system-s390x)
>>                 #4  0x000003ff943d150a __makecontext_ret (libc.so.6)
>>
>> this is with patch 2-4 plus the removal of virtio_queue_host_notifier_read.
>>
>> Without removing virtio_queue_host_notifier_read, I get the same mutex 
>> lockup (as expected).
>>
>> Maybe we have two independent issues here and this is some old bug in glibc 
>> or
>> whatever?
> 
> I'm happy to try and reproduce on x86 if you give me some instruction
> (RHEL7 should be close enough to Fedora 20).
> 
> Can you add an assert in virtio_blk_handle_output to catch reentrancy, like

that was quick (let me know if I should recompile with debugging)

(gdb) thread apply all bt

Thread 5 (Thread 0x3ff7b8ff910 (LWP 236419)):
#0  0x000003ff7cdfcf56 in syscall () from /lib64/libc.so.6
#1  0x000000001022452e in futex_wait (val=<optimized out>, ev=<optimized out>) 
at /home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:292
#2  qemu_event_wait (address@hidden <rcu_call_ready_event>) at 
/home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:399
#3  0x000000001023353a in call_rcu_thread (opaque=<optimized out>) at 
/home/cborntra/REPOS/qemu/util/rcu.c:250
#4  0x000003ff7cf084c6 in start_thread () from /lib64/libpthread.so.0
#5  0x000003ff7ce02ec2 in thread_start () from /lib64/libc.so.6

Thread 4 (Thread 0x3ff78eca910 (LWP 236426)):
#0  0x000003ff7cdf819a in ioctl () from /lib64/libc.so.6
#1  0x000000001005ddf8 in kvm_vcpu_ioctl (address@hidden, address@hidden) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1984
#2  0x000000001005df1c in kvm_cpu_exec (address@hidden) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1834
#3  0x000000001004b1be in qemu_kvm_cpu_thread_fn (arg=0x10c27d40) at 
/home/cborntra/REPOS/qemu/cpus.c:1050
#4  0x000003ff7cf084c6 in start_thread () from /lib64/libpthread.so.0
#5  0x000003ff7ce02ec2 in thread_start () from /lib64/libc.so.6

Thread 3 (Thread 0x3ff7e8dcbb0 (LWP 236395)):
#0  0x000003ff7cdf66e6 in ppoll () from /lib64/libc.so.6
#1  0x00000000101a5e08 in ppoll (__ss=0x0, __timeout=0x3ffd6afe8a0, 
__nfds=<optimized out>, __fds=<optimized out>) at /usr/include/bits/poll2.h:77
#2  qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>, address@hidden) at 
/home/cborntra/REPOS/qemu/qemu-timer.c:325
#3  0x00000000101a56f2 in os_host_main_loop_wait (timeout=1034000000) at 
/home/cborntra/REPOS/qemu/main-loop.c:251
#4  main_loop_wait (nonblocking=<optimized out>) at 
/home/cborntra/REPOS/qemu/main-loop.c:505
#5  0x00000000100136d6 in main_loop () at /home/cborntra/REPOS/qemu/vl.c:1933
#6  main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at 
/home/cborntra/REPOS/qemu/vl.c:4656

Thread 2 (Thread 0x3ff7b0ff910 (LWP 236421)):
#0  0x000003ff7cdf66e6 in ppoll () from /lib64/libc.so.6
#1  0x00000000101a5e28 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized 
out>, __fds=<optimized out>) at /usr/include/bits/poll2.h:77
#2  qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>, address@hidden) at 
/home/cborntra/REPOS/qemu/qemu-timer.c:313
#3  0x00000000101a727c in aio_poll (ctx=0x10880560, blocking=<optimized out>) 
at /home/cborntra/REPOS/qemu/aio-posix.c:453
#4  0x00000000100d39f0 in iothread_run (opaque=0x10880020) at 
/home/cborntra/REPOS/qemu/iothread.c:46
#5  0x000003ff7cf084c6 in start_thread () from /lib64/libpthread.so.0
#6  0x000003ff7ce02ec2 in thread_start () from /lib64/libc.so.6

Thread 1 (Thread 0x3ff57fff910 (LWP 236427)):
#0  0x000003ff7cd3b650 in raise () from /lib64/libc.so.6
#1  0x000003ff7cd3ced8 in abort () from /lib64/libc.so.6
#2  0x000003ff7cd33666 in __assert_fail_base () from /lib64/libc.so.6
#3  0x000003ff7cd336f4 in __assert_fail () from /lib64/libc.so.6
#4  0x000000001007a3c4 in virtio_blk_handle_output (vdev=<optimized out>, 
vq=<optimized out>) at /home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:595
#5  0x000000001009390e in virtio_queue_notify_vq (vq=0x10d77c70) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1095
#6  0x0000000010095894 in virtio_queue_notify_vq (vq=<optimized out>) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1091
#7  virtio_queue_notify (vdev=<optimized out>, address@hidden) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1101
#8  0x00000000100a17c8 in virtio_ccw_hcall_notify (args=<optimized out>) at 
/home/cborntra/REPOS/qemu/hw/s390x/s390-virtio-ccw.c:66
#9  0x000000001009c210 in s390_virtio_hypercall (address@hidden) at 
/home/cborntra/REPOS/qemu/hw/s390x/s390-virtio-hcall.c:35
#10 0x00000000100cb4e8 in handle_hypercall (run=<optimized out>, 
cpu=0x10c6d7d0) at /home/cborntra/REPOS/qemu/target-s390x/kvm.c:1283
#11 handle_diag (ipb=<optimized out>, run=0x3ff78680000, cpu=0x10c6d7d0) at 
/home/cborntra/REPOS/qemu/target-s390x/kvm.c:1352
#12 handle_instruction (run=0x3ff78680000, cpu=0x10c6d7d0) at 
/home/cborntra/REPOS/qemu/target-s390x/kvm.c:1799
#13 handle_intercept (cpu=0x10c6d7d0) at 
/home/cborntra/REPOS/qemu/target-s390x/kvm.c:1842
#14 kvm_arch_handle_exit (address@hidden, address@hidden) at 
/home/cborntra/REPOS/qemu/target-s390x/kvm.c:2028
#15 0x000000001005df70 in kvm_cpu_exec (address@hidden) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1921
#16 0x000000001004b1be in qemu_kvm_cpu_thread_fn (arg=0x10c6d7d0) at 
/home/cborntra/REPOS/qemu/cpus.c:1050
#17 0x000003ff7cf084c6 in start_thread () from /lib64/libpthread.so.0
#18 0x000003ff7ce02ec2 in thread_start () from /lib64/libc.so.6