From: Anton Nefedov <anton.nefe...@virtuozzo.com>
Socket backend read handler should normally perform a disconnect, however
the read handler may not get a chance to run if the frontend is not ready
(qemu_chr_be_can_write == 0).
This means that in virtio-serial frontend case if
- the host has disconnected (giving EPIPE on socket write)
- and the guest has disconnected (-> frontend not ready -> backend
will not read)
- and there is still data (frontend->backend) to flush (has to be a really
tricky timing but nevertheless, we have observed the case in production)
This results in virtio-serial trying to flush this data continiously forming
a busy loop.
Solution: react on EPIPE in the socket write handler. We must not disconnect
right away though, there still may be data to read (see 4bf1cb0).
Signed-off-by: Anton Nefedov <anton.nefe...@virtuozzo.com>
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Paolo Bonzini <pbonz...@redhat.com>
CC: Daniel P. Berrange <berra...@redhat.com>
---
qemu-char.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/qemu-char.c b/qemu-char.c
index 6b4a299..f1f7a07 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -1202,7 +1202,7 @@ static int io_channel_send_full(QIOChannel *ioc,
errno = EAGAIN;
return -1;
} else if (ret < 0) {
- errno = EINVAL;
+ errno = errno == EPIPE ? EPIPE : EINVAL;
return -1;
}
@@ -2854,6 +2854,9 @@ static gboolean tcp_chr_accept(QIOChannel *chan,
GIOCondition cond,
void *opaque);
+static int tcp_chr_read_poll(void *opaque);
+static void tcp_chr_disconnect(Chardev *chr);
+
/* Called with chr_write_lock held. */
static int tcp_chr_write(Chardev *chr, const uint8_t *buf, int len)
{
@@ -2871,6 +2874,13 @@ static int tcp_chr_write(Chardev *chr, const uint8_t
*buf, int len)
s->write_msgfds_num = 0;
}
+ if (ret < 0 && errno == EPIPE) {
+ if (tcp_chr_read_poll(chr) <= 0) {
+ tcp_chr_disconnect(chr);
+ return len;
+ } /* else let the read handler finish it properly */
+ }
+
return ret;
} else {
/* XXX: indicate an error ? */
--
2.7.4
