Anton Nefedov
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b0a335e351
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qemu-char: socket backend: disconnect on write error
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 write error in the socket write handler.
errno is not reliable after qio_channel_writev_full(), so we may not get
the exact EPIPE, so disconnect on any error but QIO_CHANNEL_ERR_BLOCK which
io_channel_send_full() converts to errno EAGAIN.
We must not disconnect right away though, there still may be data to read
(see 4bf1cb0).
Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Daniel P. Berrange <berrange@redhat.com>
CC: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1486045589-8074-1-git-send-email-den@openvz.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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2017-02-16 14:06:55 +01:00 |
Marc-André Lureau