Re: I finally prepared a testcase for read(inotify_fd) getting EINTRon PTRACE_ATTACH

[Denys Vlasenko]

On 02/10/2012 04:09 PM, Oleg Nesterov wrote:
> On 02/10, Oleg Nesterov wrote:
> > At first glance this looks obvious? I never used inotify and I never
> > looked into fs/notify/inotify/, but it seems that inotify_read() simply
> > returns -EINTR if signal_pending() and doesn't implement restarts.
> >
> > Probably this trivial change
> >
> > 	--- x/fs/notify/inotify/inotify_user.c
> > 	+++ x/fs/notify/inotify/inotify_user.c
> > 	@@ -264,7 +264,7 @@ static ssize_t inotify_read(struct file
> > 			ret = -EAGAIN;
> > 			if (file->f_flags&  O_NONBLOCK)
> > 				break;
> > 	-		ret = -EINTR;
> > 	+		ret = -ERESTARTSYS;
> > 			if (signal_pending(current))
> > 				break;
> >
> >
> > makes sense.
>
> except I meant -ERESTARTNOHAND to avoid the behavioural change.

I run-tested the fix. It works: testcase no longer fails
(modulo incorrect logic in the testcase which wase not working
properly on "no bug detected" code path. Fixed one:
http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/eintr-on-attach.c?cvsroot=systemtap
)

I'm not sure inotify really wants to deviate from other reads
and return -EINTR even for SA_RESTARTing signals. IOW:
I think -ERESTARTSYS here would be more correct than -ERESTARTNOHAND.

If -ERESTARTNOHAND is really what inotify people want, they need to
add a comment about it.

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vda
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