On Wed, 2019-04-03 at 08:55 -0400, Steven Rostedt wrote:
> On Tue, 2 Apr 2019 16:45:40 +0300
> Slavomir Kaslev <kaslevs@xxxxxxxxxx> wrote:
>
> > +/*
> > + * Returns -1 on error.
> > + * or bytes of data read.
> > + */
> > +static long direct_splice_data(struct tracecmd_recorder *recorder)
> > +{
> > + struct pollfd pfd = {
> > + .fd = recorder->trace_fd,
> > + .events = POLLIN,
> > + };
> > + long read;
> > + int ret;
> > +
> > + ret = poll(&pfd, 1, POLL_TIMEOUT_MS);
> > + if (ret < 0)
> > + return -1;
> > +
> > + if (!(pfd.revents | POLLIN))
> > + return 0;
>
> Why the polling code, and not just block on splice?
To work around older kernels that don't have the splice(2)
O_NONBLOCKING fix[1] for pipes.
An alternative would be to configure SIGINT not to auto restart
syscalls (which is the default afaik). Then splice(2) will return
EAGAIN and will can restart it with SPLICE_F_NONBLOCK flag on.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee5e001196d1345b8fee25925ff5f1d67936081e
|