On 30.01.2018 20:49, Paolo Bonzini wrote:
> On 25/01/2018 08:51, Klim Kireev wrote:
>> The following behavior was observed for QEMU configured by libvirt
>> to use guest agent as usual for the guests without virtio-serial
>> driver (Windows or the guest remaining in BIOS stage).
>>
>> In QEMU on first connect to listen character device socket
>> the listen socket is removed from poll just after the accept().
>> virtio_serial_guest_ready() returns 0 and the descriptor
>> of the connected Unix socket is removed from poll and it will
>> not be present in poll() until the guest will initialize the driver
>> and change the state of the serial to "guest connected".
>>
>> In libvirt connect() to guest agent is performed on restart and
>> is run under VM state lock. Connect() is blocking and can
>> wait forever.
>> In this case libvirt can not perform ANY operation on that VM.
>>
>> The bug can be easily reproduced this way:
>>
>> Terminal 1:
>> qemu-system-x86_64 -m 512 -device pci-serial,chardev=serial1 -chardev
>> socket,id=serial1,path=/tmp/console.sock,server,nowait
>> (virtio-serial and isa-serial also fit)
>>
>> Terminal 2:
>> minicom -D unix\#/tmp/console.sock
>> (type something and press enter)
>> C-a x (to exit)
>>
>> Do 3 times:
>> minicom -D unix\#/tmp/console.sock
>> C-a x
>>
>> It needs 4 connections, because the first one is accepted by QEMU, then two
>> are queued by
>> the kernel, and the 4th blocks.
>>
>> The problem is that QEMU doesn't add a read watcher after succesful read
>> until the guest device wants to acquire recieved data, so
>> I propose to install a separate pullhup watcher regardless of
>> whether the device waits for data or not.
>>
>> Signed-off-by: Klim Kireev <klim.kir...@virtuozzo.com>
>> ---
>> Changelog:
>> v2: Remove timer as a redundant feature
>>
>> v3: Remove read call and return G_SOURCE_REMOVE
>>
>> v4: Move to GSource API
>>
>> v5: Fix git typos
>>
>> chardev/char-socket.c | 22 ++++++++++++++++++++++
>> 1 file changed, 22 insertions(+)
>>
>> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
>> index 77cdf487eb..a340af6cd3 100644
>> --- a/chardev/char-socket.c
>> +++ b/chardev/char-socket.c
>> @@ -42,6 +42,7 @@ typedef struct {
>> QIOChannel *ioc; /* Client I/O channel */
>> QIOChannelSocket *sioc; /* Client master channel */
>> QIONetListener *listener;
>> + GSource *hup_source;
>> QCryptoTLSCreds *tls_creds;
>> int connected;
>> int max_size;
>> @@ -352,6 +353,12 @@ static void tcp_chr_free_connection(Chardev *chr)
>> s->read_msgfds_num = 0;
>> }
>>
>> + if (s->hup_source != NULL) {
>> + g_source_destroy(s->hup_source);
>> + g_source_unref(s->hup_source);
>> + s->hup_source = NULL;
>> + }
>> +
>> tcp_set_msgfds(chr, NULL, 0);
>> remove_fd_in_watch(chr);
>> object_unref(OBJECT(s->sioc));
>> @@ -455,6 +462,15 @@ static gboolean tcp_chr_read(QIOChannel *chan,
>> GIOCondition cond, void *opaque)
>> return TRUE;
>> }
>>
>> +static gboolean tcp_chr_hup(QIOChannel *channel,
>> + GIOCondition cond,
>> + void *opaque)
>> +{
>> + Chardev *chr = CHARDEV(opaque);
>> + tcp_chr_disconnect(chr);
>> + return G_SOURCE_REMOVE;
>> +}
>> +
>> static int tcp_chr_sync_read(Chardev *chr, const uint8_t *buf, int len)
>> {
>> SocketChardev *s = SOCKET_CHARDEV(chr);
>> @@ -528,6 +544,12 @@ static void tcp_chr_connect(void *opaque)
>> tcp_chr_read,
>> chr, chr->gcontext);
>> }
>> +
>> + s->hup_source = qio_channel_create_watch(s->ioc, G_IO_HUP);
>> + g_source_set_callback(s->hup_source, (GSourceFunc)tcp_chr_hup,
>> + chr, NULL);
>> + g_source_attach(s->hup_source, chr->gcontext);
>> +
>> qemu_chr_be_event(chr, CHR_EVENT_OPENED);
>> }
>>
>>
>
> Queued, thanks.
Hi!
I'm currently facing some issues with "make check -j4" (i.e. running the
tests in parallel). Git bisect blames this commit - though I'm not sure
whether this is really the right one ... Starting with this commit, I
saw hangs in test-filter-redirector, but git master rather seems to hang
with vhost-user-test instead.
Stefan also had issues with "make check -j4" today, so it's apparently
not only me ... can somebody else reproduce the problem with the git
master branch?
Thomas
