netdev - Re: [PATCH v2 11/11] vsock_test: wait for the remote to close the connection

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Date:   Thu, 22 Aug 2019 11:15:46 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
Cc:     netdev@...r.kernel.org, kvm@...r.kernel.org,
        Dexuan Cui <decui@...rosoft.com>,
        virtualization@...ts.linux-foundation.org,
        "David S. Miller" <davem@...emloft.net>,
        Jorgen Hansen <jhansen@...are.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/11] vsock_test: wait for the remote to close the
 connection

On Tue, Aug 20, 2019 at 09:28:28AM +0100, Stefan Hajnoczi wrote:
> On Thu, Aug 01, 2019 at 05:25:41PM +0200, Stefano Garzarella wrote:
> > +/* Wait for the remote to close the connection */
> > +void vsock_wait_remote_close(int fd)
> > +{
> > +	struct epoll_event ev;
> > +	int epollfd, nfds;
> > +
> > +	epollfd = epoll_create1(0);
> > +	if (epollfd == -1) {
> > +		perror("epoll_create1");
> > +		exit(EXIT_FAILURE);
> > +	}
> > +
> > +	ev.events = EPOLLRDHUP | EPOLLHUP;
> > +	ev.data.fd = fd;
> > +	if (epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &ev) == -1) {
> > +		perror("epoll_ctl");
> > +		exit(EXIT_FAILURE);
> > +	}
> > +
> > +	nfds = epoll_wait(epollfd, &ev, 1, TIMEOUT * 1000);
> > +	if (nfds == -1) {
> > +		perror("epoll_wait");
> > +		exit(EXIT_FAILURE);
> > +	}
> > +
> > +	if (nfds == 0) {
> > +		fprintf(stderr, "epoll_wait timed out\n");
> > +		exit(EXIT_FAILURE);
> > +	}
> > +
> > +	assert(nfds == 1);
> > +	assert(ev.events & (EPOLLRDHUP | EPOLLHUP));
> > +	assert(ev.data.fd == fd);
> > +
> > +	close(epollfd);
> > +}
> 
> Please use timeout_begin()/timeout_end() so that the test cannot hang.
> 

I used the TIMEOUT macro in the epoll_wait() to avoid the hang.
Do you think is better to use the timeout_begin()/timeout_end()?
In this case, should I remove the timeout in the epoll_wait()?

> > diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
> > index 64adf45501ca..a664675bec5a 100644
> > --- a/tools/testing/vsock/vsock_test.c
> > +++ b/tools/testing/vsock/vsock_test.c
> > @@ -84,6 +84,11 @@ static void test_stream_client_close_server(const struct test_opts *opts)
> >  
> >  	control_expectln("CLOSED");
> >  
> > +	/* Wait for the remote to close the connection, before check
> > +	 * -EPIPE error on send.
> > +	 */
> > +	vsock_wait_remote_close(fd);
> 
> Is control_expectln("CLOSED") still necessary now that we're waiting for
> the poll event?  The control message was an attempt to wait until the
> other side closed the socket.

Right, I'll remove it in the v3

Thanks,
Stefano