Re: [Qemu-devel] [PATCH] virtio-blk: assert on starting/stopping

[Christian Borntraeger]

On 04/03/2016 12:37 PM, Michael S. Tsirkin wrote:
> Reentrancy cannot happen while the BQL is being held,
> so we should never enter this condition.
> 
> Cc: Christian Borntraeger <address@hidden>
> Cc: Cornelia Huck <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
> 
> This is a replacement for [PATCH 9/9] virtio: remove starting/stopping
> checks Christian, could you please give it a spin with debug enabled?
> Since you reported above Paolo's patch triggers segfaults, I expect this
> one to trigger assertions as well, which should give us more info on
> the root cause.
> 


the assert triggered (see below). 


(gdb) thread apply all bt

Thread 5 (Thread 0x3ffa9fff910 (LWP 41714)):
#0  0x000003ffab68841e in syscall () at /lib64/libc.so.6
#1  0x00000000803e84f6 in futex_wait (ev=0x80a65bd4 <rcu_call_ready_event>, 
val=4294967295) at /home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:292
#2  0x00000000803e8786 in qemu_event_wait (ev=0x80a65bd4 
<rcu_call_ready_event>) at 
/home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:399
#3  0x0000000080405ec4 in call_rcu_thread (opaque=0x0) at 
/home/cborntra/REPOS/qemu/util/rcu.c:250
#4  0x000003ffab787c2c in start_thread () at /lib64/libpthread.so.0
#5  0x000003ffab68ec9a in thread_start () at /lib64/libc.so.6

Thread 4 (Thread 0x3ffa97ff910 (LWP 41718)):
#0  0x000000008001b09a in address_space_read_continue (as=0x805da230 
<address_space_memory>, addr=350645744, attrs=..., buf=0x3ffa97f8450 "", len=0, 
addr1=350645728, l=16, mr=0x80b0d6a0)
    at /home/cborntra/REPOS/qemu/exec.c:2738
#1  0x000000008001b186 in address_space_read_full (as=0x805da230 
<address_space_memory>, addr=350645728, attrs=..., buf=0x3ffa97f8440 
"\230\001q\024", len=16)
    at /home/cborntra/REPOS/qemu/exec.c:2752
#2  0x00000000800ed284 in vring_desc_read (len=16, buf=0x3ffa97f8440 
"\230\001q\024", attrs=..., addr=350645728, as=0x805da230 
<address_space_memory>)
    at /home/cborntra/REPOS/qemu/include/exec/memory.h:1431
#3  0x00000000800ed284 in vring_desc_read (vdev=0x80e44b88, desc=0x3ffa97f8440, 
desc_pa=350645696, i=2) at /home/cborntra/REPOS/qemu/hw/virtio/virtio.c:124
#4  0x00000000800ee05e in virtqueue_read_next_desc (vdev=0x80e44b88, 
desc=0x3ffa97f8440, desc_pa=350645696, max=3) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:366
#5  0x00000000800eecbe in virtqueue_pop (vq=0x80f221c0, sz=160) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:602
#6  0x00000000800b40b0 in virtio_blk_get_request (s=0x80e44b88) at 
/home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:192
#7  0x00000000800b56e0 in virtio_blk_handle_vq (s=0x80e44b88, vq=0x80f221c0) at 
/home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:588
#8  0x00000000800b78a2 in virtio_blk_data_plane_handle_output (vdev=0x80e44b88, 
vq=0x80f221c0) at /home/cborntra/REPOS/qemu/hw/block/dataplane/virtio-blk.c:195
#9  0x00000000800f0cb4 in virtio_queue_notify_aio_vq (vq=0x80f221c0) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1098
#10 0x00000000800f3664 in virtio_queue_host_notifier_aio_read (n=0x80f22220) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1799
#11 0x00000000802f1a0c in aio_dispatch (ctx=0x80acd5d0) at 
/home/cborntra/REPOS/qemu/aio-posix.c:327
#12 0x00000000802f2392 in aio_poll (ctx=0x80acd5d0, blocking=true) at 
/home/cborntra/REPOS/qemu/aio-posix.c:475
#13 0x000000008016590a in iothread_run (opaque=0x80acd090) at 
/home/cborntra/REPOS/qemu/iothread.c:46
#14 0x000003ffab787c2c in start_thread () at /lib64/libpthread.so.0
#15 0x000003ffab68ec9a in thread_start () at /lib64/libc.so.6

Thread 3 (Thread 0x3ff8b9d2910 (LWP 41739)):
#0  0x000003ffab68334a in ioctl () at /lib64/libc.so.6
#1  0x0000000080081c84 in kvm_vcpu_ioctl (cpu=0x80e4d2b0, type=44672) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1984
#2  0x000000008008154c in kvm_cpu_exec (cpu=0x80e4d2b0) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1834
#3  0x000000008006075c in qemu_kvm_cpu_thread_fn (arg=0x80e4d2b0) at 
/home/cborntra/REPOS/qemu/cpus.c:1056
#4  0x000003ffab787c2c in start_thread () at /lib64/libpthread.so.0
#5  0x000003ffab68ec9a in thread_start () at /lib64/libc.so.6

Thread 2 (Thread 0x3ff8b1d2910 (LWP 41743)):
#0  0x000003ffab68334a in ioctl () at /lib64/libc.so.6
#1  0x0000000080081c84 in kvm_vcpu_ioctl (cpu=0x80b40040, type=44672) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1984
#2  0x000000008008154c in kvm_cpu_exec (cpu=0x80b40040) at 
/home/cborntra/REPOS/qemu/kvm-all.c:1834
#3  0x000000008006075c in qemu_kvm_cpu_thread_fn (arg=0x80b40040) at 
/home/cborntra/REPOS/qemu/cpus.c:1056
#4  0x000003ffab787c2c in start_thread () at /lib64/libpthread.so.0
#5  0x000003ffab68ec9a in thread_start () at /lib64/libc.so.6

Thread 1 (Thread 0x3ffad25bb90 (LWP 41685)):
---Type <return> to continue, or q <return> to quit---
#0  0x000003ffab5be2c0 in raise () at /lib64/libc.so.6
#1  0x000003ffab5bfc26 in abort () at /lib64/libc.so.6
#2  0x000003ffab5b5bce in __assert_fail_base () at /lib64/libc.so.6
#3  0x000003ffab5b5c5c in  () at /lib64/libc.so.6
#4  0x00000000800b79e4 in virtio_blk_data_plane_start (s=0x80b195a0) at 
/home/cborntra/REPOS/qemu/hw/block/dataplane/virtio-blk.c:210
#5  0x00000000800b57ba in virtio_blk_handle_output (vdev=0x80e4b0f8, 
vq=0x80eaa180) at /home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:607
#6  0x00000000800f0d74 in virtio_queue_notify_vq (vq=0x80eaa180) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1108
#7  0x00000000800f376c in virtio_queue_host_notifier_read (n=0x80eaa1e0) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1820
#8  0x00000000800f381c in virtio_queue_set_host_notifier_fd_handler 
(vq=0x80eaa180, assign=false, set_handler=false) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1836
#9  0x000000008010b808 in virtio_ccw_set_guest2host_notifier (dev=0x80e49fb0, 
n=0, assign=false, set_handler=false) at 
/home/cborntra/REPOS/qemu/hw/s390x/virtio-ccw.c:98
#10 0x000000008010baaa in virtio_ccw_stop_ioeventfd (dev=0x80e49fb0) at 
/home/cborntra/REPOS/qemu/hw/s390x/virtio-ccw.c:155
#11 0x000000008010f162 in virtio_ccw_set_host_notifier (d=0x80e49fb0, n=0, 
assign=true) at /home/cborntra/REPOS/qemu/hw/s390x/virtio-ccw.c:1212
#12 0x00000000800b7ab0 in virtio_blk_data_plane_start (s=0x80b195a0) at 
/home/cborntra/REPOS/qemu/hw/block/dataplane/virtio-blk.c:225
#13 0x00000000800b57ba in virtio_blk_handle_output (vdev=0x80e4b0f8, 
vq=0x80eaa180) at /home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:607
#14 0x00000000800f0d74 in virtio_queue_notify_vq (vq=0x80eaa180) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1108
#15 0x00000000800f376c in virtio_queue_host_notifier_read (n=0x80eaa1e0) at 
/home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1820
#16 0x00000000802f1a0c in aio_dispatch (ctx=0x80abae30) at 
/home/cborntra/REPOS/qemu/aio-posix.c:327
#17 0x00000000802df4d4 in aio_ctx_dispatch (source=0x80abae30, callback=0x0, 
user_data=0x0) at /home/cborntra/REPOS/qemu/async.c:233
#18 0x000003ffabfd1c0a in g_main_context_dispatch () at /lib64/libglib-2.0.so.0
#19 0x00000000802ee70e in glib_pollfds_poll () at 
/home/cborntra/REPOS/qemu/main-loop.c:213
#20 0x00000000802ee84a in os_host_main_loop_wait (timeout=1472000000) at 
/home/cborntra/REPOS/qemu/main-loop.c:258
#21 0x00000000802ee956 in main_loop_wait (nonblocking=0) at 
/home/cborntra/REPOS/qemu/main-loop.c:506
#22 0x000000008017dc0c in main_loop () at /home/cborntra/REPOS/qemu/vl.c:1934
#23 0x00000000801860e0 in main (argc=72, argv=0x3ffd60fe838, 
envp=0x3ffd60fea80) at /home/cborntra/REPOS/qemu/vl.c:4652