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Subject: Re: [Qemu-devel] [PATCH v2 03/15] sheepdog: move coroutine
 send/recv function to generic code
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To: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org

On 09/17/2011 08:29 AM, MORITA Kazutaka wrote:
>> >  +#else
>> >  +        struct iovec *p = iov;
>> >  +        ret = 0;
>> >  +        while (iovlen>  0) {
>> >  +            int rc;
>> >  +            if (do_sendv) {
>> >  +                rc = send(sockfd, p->iov_base, p->iov_len, 0);
>> >  +            } else {
>> >  +                rc = qemu_recv(sockfd, p->iov_base, p->iov_len, 0);
>> >  +            }
>> >  +            if (rc == -1) {
>> >  +                if (errno == EINTR) {
>> >  +                    continue;
>> >  +                }
>> >  +                if (ret == 0) {
>> >  +                    ret = -1;
>> >  +                }
>> >  +                break;
>> >  +            }
>> >  +            iovlen--, p++;
>> >  +            ret += rc;
>> >  +        }
> This code can be called inside coroutines with a non-blocking fd, so
> should we avoid busy waiting?

It doesn't busy wait, it exits with EAGAIN.  I'll squash in here the 
first hunk of patch 4, which is needed.

qemu_co_recvv already handles reads that return zero, unlike sheepdog's 
do_readv_writev.  I probably moved it there inadvertently while moving 
code around to cutils.c, but in order to fix qemu-ga I need to create a 
new file qemu-coroutine-io.c.

Kevin, do you want me to resubmit everything, or are you going to apply 
some more patches to the block branch (5 to 12 should be fine)?

Paolo