Re: [Qemu-devel] [PATCH 11/18] vhost-user: add shutdown support

[Marc-André Lureau]

On Wed, Apr 13, 2016 at 7:32 PM, Yuanhan Liu
<address@hidden> wrote:
>>
>> > I'm asking because I found a seg fault issue sometimes,
>> > due to opaque is NULL.
>
> Oh, I was wrong, it's u being NULL, but not opaque.
>> >
>>
>> I would be interested to see the backtrace or have a reproducer.
>
> It's a normal test steps: start a vhost-user switch (I'm using DPDK
> vhost-switch example), kill it, and wait for a while (something like
> more than 10s or even longer), then I saw a seg fault:
>
>     (gdb) p dev
>     $4 = (struct vhost_dev *) 0x555556571bf0
>     (gdb) p u
>     $5 = (struct vhost_user *) 0x0
>     (gdb) where
>     #0  0x0000555555798612 in slave_read (opaque=0x555556571bf0)
>         at /home/yliu/qemu/hw/virtio/vhost-user.c:539
>     #1  0x0000555555a343a4 in aio_dispatch (ctx=0x55555655f560) at 
> /home/yliu/qemu/aio-posix.c:327
>     #2  0x0000555555a2738b in aio_ctx_dispatch (source=0x55555655f560, 
> callback=0x0, user_data=0x0)
>         at /home/yliu/qemu/async.c:233
>     #3  0x00007ffff51032a6 in g_main_context_dispatch () from 
> /lib64/libglib-2.0.so.0
>     #4  0x0000555555a3239e in glib_pollfds_poll () at 
> /home/yliu/qemu/main-loop.c:213
>     #5  0x0000555555a3247b in os_host_main_loop_wait (timeout=29875848) at 
> /home/yliu/qemu/main-loop.c:258
>     #6  0x0000555555a3252b in main_loop_wait (nonblocking=0) at 
> /home/yliu/qemu/main-loop.c:506
>     #7  0x0000555555846e35 in main_loop () at /home/yliu/qemu/vl.c:1934
>     #8  0x000055555584e6bf in main (argc=31, argv=0x7fffffffe078, 
> envp=0x7fffffffe178)
>         at /home/yliu/qemu/vl.c:4658
>

This patch set doesn't try to handle crashes from backend. This would
require a much more detailed study of the existing code path. A lot of
places assume the backend is fully working as expected. I think
handling backend crashes should be a different, later, patch set.



-- 
Marc-André Lureau