Re: [Qemu-devel] [PATCH v4 2/2] char-socket: Lock tcp_chr_disconnect() and socket_reconnect_timeout()

From: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	"berto@igalia.com" <berto@igalia.com>,
	Denis Lunev <den@virtuozzo.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"marcandre.lureau@redhat.com" <marcandre.lureau@redhat.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v4 2/2] char-socket: Lock tcp_chr_disconnect() and socket_reconnect_timeout()
Date: Tue, 20 Aug 2019 11:10:20 +0000	[thread overview]
Message-ID: <40430de6-9159-f8d0-f140-0a862526f8b9@virtuozzo.com> (raw)
In-Reply-To: <20190820095800.GF23352@redhat.com>


On 20/08/2019 12:58, Daniel P. Berrangé wrote:
> On Mon, Aug 12, 2019 at 06:58:29PM +0300, Andrey Shinkevich wrote:
>> From: Alberto Garcia <berto@igalia.com>
>>
>> There's a race condition in which the tcp_chr_read() ioc handler can
>> close a connection that is being written to from another thread.
>>
>> Running iotest 136 in a loop triggers this problem and crashes QEMU.
>>
>>   (gdb) bt
>>   #0  0x00005558b842902d in object_get_class (obj=0x0) at qom/object.c:860
>>   #1  0x00005558b84f92db in qio_channel_writev_full (ioc=0x0, iov=0x7ffc355decf0, niov=1, fds=0x0, nfds=0, errp=0x0) at io/channel.c:76
>>   #2  0x00005558b84e0e9e in io_channel_send_full (ioc=0x0, buf=0x5558baf5beb0, len=138, fds=0x0, nfds=0) at chardev/char-io.c:123
>>   #3  0x00005558b84e4a69 in tcp_chr_write (chr=0x5558ba460380, buf=0x5558baf5beb0 "...", len=138) at chardev/char-socket.c:135
>>   #4  0x00005558b84dca55 in qemu_chr_write_buffer (s=0x5558ba460380, buf=0x5558baf5beb0 "...", len=138, offset=0x7ffc355dedd0, write_all=false) at chardev/char.c:112
>>   #5  0x00005558b84dcbc2 in qemu_chr_write (s=0x5558ba460380, buf=0x5558baf5beb0 "...", len=138, write_all=false) at chardev/char.c:147
>>   #6  0x00005558b84dfb26 in qemu_chr_fe_write (be=0x5558ba476610, buf=0x5558baf5beb0 "...", len=138) at chardev/char-fe.c:42
>>   #7  0x00005558b8088c86 in monitor_flush_locked (mon=0x5558ba476610) at monitor.c:406
>>   #8  0x00005558b8088e8c in monitor_puts (mon=0x5558ba476610, str=0x5558ba921e49 "") at monitor.c:449
>>   #9  0x00005558b8089178 in qmp_send_response (mon=0x5558ba476610, rsp=0x5558bb161600) at monitor.c:498
>>   #10 0x00005558b808920c in monitor_qapi_event_emit (event=QAPI_EVENT_SHUTDOWN, qdict=0x5558bb161600) at monitor.c:526
>>   #11 0x00005558b8089307 in monitor_qapi_event_queue_no_reenter (event=QAPI_EVENT_SHUTDOWN, qdict=0x5558bb161600) at monitor.c:551
>>   #12 0x00005558b80896c0 in qapi_event_emit (event=QAPI_EVENT_SHUTDOWN, qdict=0x5558bb161600) at monitor.c:626
>>   #13 0x00005558b855f23b in qapi_event_send_shutdown (guest=false, reason=SHUTDOWN_CAUSE_HOST_QMP_QUIT) at qapi/qapi-events-run-state.c:43
>>   #14 0x00005558b81911ef in qemu_system_shutdown (cause=SHUTDOWN_CAUSE_HOST_QMP_QUIT) at vl.c:1837
>>   #15 0x00005558b8191308 in main_loop_should_exit () at vl.c:1885
>>   #16 0x00005558b819140d in main_loop () at vl.c:1924
>>   #17 0x00005558b8198c84 in main (argc=18, argv=0x7ffc355df3f8, envp=0x7ffc355df490) at vl.c:4665
>>
>> This patch adds a lock to protect tcp_chr_disconnect() and
>> socket_reconnect_timeout()
>>
>> Signed-off-by: Alberto Garcia <berto@igalia.com>
>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> 
> 
> Regards,
> Daniel
> 

Thank you Daniel
Andrey
-- 
With the best regards,
Andrey Shinkevich