On Mon, Nov 14, 2011 at 01:34:46PM +0100, Jan Kara wrote:
> On Mon 14-11-11 20:15:56, Wu Fengguang wrote:
> > > @@ -2407,6 +2407,10 @@ static ssize_t generic_perform_write(struct file *file,
> > > iov_iter_count(i));
> > >
> > > again:
> > > + if (signal_pending(current)) {
> >
> > signal_pending looks more useful than fatal_signal_pending in that it
> > covers normal signals too. However it's exactly the broader coverage
> > that makes it an interface change -- will this possibly break casually
> > written applications?
> Yeah, this is upto discussion. Historically, write() (or any other system
> call) could have returned EINTR. In fact, write() to a socket can return
> EINTR even now. But you are right that we didn't return EINTR from write()
> to a regular file. So if you prefer to never return EINTR from a write to a
> regular file, I can change the check since I'm also slightly worried that
> some badly written app can notice.
No, this is not up for discussion. You can't return short writes (or
reads). This is why the 'fatal_signal_pending' API exists -- if the
signal is fatal, the task is never returned to, so its bug (not checking
the return from read/write) is not exposed.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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