On 03/17/2016 04:15 PM, Christian Borntraeger wrote: > 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 (ev=ev@entry=0x1082b5c4 <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 (cpu=cpu@entry=0x10c27d40, > type=type@entry=44672) at /home/cborntra/REPOS/qemu/kvm-all.c:1984 > #2 0x000000001005df1c in kvm_cpu_exec (cpu=cpu@entry=0x10c27d40) 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>, > timeout=timeout@entry=1034000000) 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>, > timeout=timeout@entry=-1) 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>, n=n@entry=0) 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 (env=env@entry=0x10c75aa0) 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
FWIW, this looks like that we still have a case, without eventfd during reboot or startup > #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 (cs=cs@entry=0x10c6d7d0, > run=run@entry=0x3ff78680000) at > /home/cborntra/REPOS/qemu/target-s390x/kvm.c:2028 > #15 0x000000001005df70 in kvm_cpu_exec (cpu=cpu@entry=0x10c6d7d0) 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 >