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

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Message-ID: <20190823100921.GD12092@stefanha-x1.localdomain>
Date:   Fri, 23 Aug 2019 11:09:21 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...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 Thu, Aug 22, 2019 at 11:15:46AM +0200, Stefano Garzarella wrote:
> 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()?

Oops, you're right.  There are no other blocking calls in this function
so the existing patch is fine.

Thanks,
Stefan

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