Re: [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread)

From: Pavel Machek <pavel@ucw.cz>
To: Anton Blanchard <anton@samba.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Oleg Nesterov <oleg@tv-sign.ru>, Andrew Morton <akpm@osdl.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Aneesh Kumar <aneesh.kumar@gmail.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	Gautham R Shenoy <ego@in.ibm.com>
Subject: Re: [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread)
Date: Tue, 20 Mar 2007 19:08:57 +0100	[thread overview]
Message-ID: <20070320180857.GC2593@elf.ucw.cz> (raw)
In-Reply-To: <20070312224524.GB807@kryten>

Hi!

> > Do not do it, then. Confusion it causes is not worth saving one line
> > of code. 
> > 
> > You do less typing, but the resulting code is _less_ readable, not
> > more.
> 
> Then please document it _clearly_ with the kthread code somewhere. The
> reason I brought this up is I had no idea we had to put the freezer gunk
> in all kernel thread loops and Ive been writing kernel threads for years.

This is in Doc*/power/kernel_threads.txt:

KERNEL THREADS

Freezer

Upon entering a suspended state the system will freeze all
tasks. This is done by delivering pseudosignals. This affects
kernel threads, too. To successfully freeze a kernel thread
the thread has to check for the pseudosignal and enter the
refrigerator. Code to do this looks like this:

        do {
                hub_events();
                wait_event_interruptible(khubd_wait,
!list_empty(&hub_event_list));
                try_to_freeze();
        } while (!signal_pending(current));

...do you know about better place?
									Pavel
-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html