[libvirt] [PATCH] fix bug libvirt daemon deadlock when another force console break down an existed console client when this deadlock hanppened, libvirtd backtrace as follow, a typical ABBA deadlock circumstance:

[Michal Privoznik]

On 11/19/19 12:39 PM, LanceLiu wrote:
> (gdb) thread 23
> [Switching to thread 23 (Thread 0x7fbb54810700 (LWP 296966))]
> (gdb) bt
>      at rpc/virnetserverclient.c:1503
>      client=client at entry=0x5641d20e20a0, msg=0x7fbb08003ab0, rerr=rerr at entry=0x7fbb5480f7b0, procedure=201,
>      type=type at entry=3, serial=9) at rpc/virnetserverprogram.c:173
>      msg=<optimized out>, rerr=rerr at entry=0x7fbb5480f7b0, procedure=<optimized out>, serial=<optimized out>)
>      at rpc/virnetserverprogram.c:222
>      opaque=opaque at entry=0x5641d20e20a0) at stream.c:246
>      force=force at entry=true) at conf/virchrdev.c:386
>      at qemu/qemu_driver.c:16188
>      st=st at entry=0x7fbb08008fc0, flags=1) at libvirt-domain.c:9363
>      rerr=0x7fbb5480fc10, msg=<optimized out>, client=0x5641d20e4e80) at remote_dispatch.h:8540
>      rerr=0x7fbb5480fc10, args=0x7fbb08005eb0, ret=<optimized out>) at remote_dispatch.h:8505
>      server=0x5641d20be420, prog=0x5641d20da580) at rpc/virnetserverprogram.c:437
>      msg=0x5641d20e9a20) at rpc/virnetserverprogram.c:307
>      srv=0x5641d20be420) at rpc/virnetserver.c:148
> ---Type <return> to continue, or q <return> to quit---
> 
> (gdb) thread 26
> [Switching to thread 26 (Thread 0x7fbb87a378c0 (LWP 295636))]
> (gdb) bt
>      at stream.c:286
>      at rpc/virnetserverclient.c:1247
>      at rpc/virnetserverclient.c:1457
>      at util/vireventpoll.c:508
> 
> Signed-off-by: LanceLiu <liu.lance.89 at gmail.com>
> ---
>   src/remote/remote_daemon_stream.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/src/remote/remote_daemon_stream.c b/src/remote/remote_daemon_stream.c
> index 1f6e783..b27348f 100644
> --- a/src/remote/remote_daemon_stream.c
> +++ b/src/remote/remote_daemon_stream.c
> @@ -284,14 +284,16 @@ daemonStreamEvent(virStreamPtr st, int events, void *opaque)
>    * -1 on fatal client error
>    */
>   static int
> -daemonStreamFilter(virNetServerClientPtr client ATTRIBUTE_UNUSED,
> +daemonStreamFilter(virNetServerClientPtr client,

This does not look rebased onto current git HEAD ;-) "Luckily", the 
problem you're fixing is still there.

>                      virNetMessagePtr msg,
>                      void *opaque)
>   {
>       daemonClientStream *stream = opaque;
>       int ret = 0;
>   
> +    virObjectUnlock(client);
>       virMutexLock(&stream->priv->lock);
> +    virObjectLock(client);
>   
>       if (msg->header.type != VIR_NET_STREAM &&
>           msg->header.type != VIR_NET_STREAM_HOLE)
> 

I've reworded the commit message, put a comment to 
virNetServerClientFilterFunc() typedef, ACKed and pushed.

Congratulations on your first libvirt contribution!

Michal