RE: which signal is sent to freeze process?

["Agarwal, Lomesh" <lomesh.agarwal@intel.com>]

This patch works for me too.

-----Original Message-----
From: Manfred Spraul [mailto:manfred@colorfullife.com] 
Sent: Tuesday, July 24, 2007 11:49 AM
To: Pavel Machek
Cc: Rafael J. Wysocki; linux-kernel@vger.kernel.org; Agarwal, Lomesh;
Nigel Cunningham
Subject: Re: which signal is sent to freeze process?

> Hi!
>
> Can you generate small testcase that demonstrates the problem?
>
> > Then what would be the correct way to handle resume process. The
other
> > way of course is to make all the applications check the errno in
case of
> > failure. But that seems more more problematic then system call
checking.
> > What do you say?
>
> Hmm, does that testcase behave correctly over SIGSTOP/SIGCONT? I'm not
> saying kernel behaves nicely here, but perhaps fixing the apps to
> check errno properly is the right thing to do? :-)
Perhaps the kernel should use ERESTARTNOHAND instead of EINTR?
The current code is more than odd:
- select() and sys_ppoll() both use ERESTARTNOHAND (i.e.: 
the functions do not return to user space with SIGSTOP/SIGCONT or
freezer())

- sys_poll() uses EINTR (i.e.: SIGSTOP/SIGCONT/freezer() return to user
space)

Attached is a patch that switches sys_poll to ERESTARTNOHAND and a poll
test app.
Boot tested with FC6.

What do you think? With ERESTARTNOHAND, poll would only return to user
space if the app has a SIGCONT handler installed.

--
	Manfred
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