linux-kernel - Re: [PATCH] ipvs: Remove unused variable ret from sync_thread

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Date:	Tue, 12 Nov 2013 15:31:52 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipvs: Remove unused variable ret from
 sync_thread_master()

On Tue, Nov 12, 2013 at 02:21:39PM -0000, David Laight wrote:
> > > @@ -1637,7 +1637,7 @@ static int sync_thread_master(void *data)
> > >  			continue;
> > >  		}
> > >  		while (ip_vs_send_sync_msg(tinfo->sock, sb->mesg) < 0) {
> > > -			int ret = __wait_event_interruptible(*sk_sleep(sk),
> > 
> > So ideally there's be a comment here why we're using interruptible but
> > then ignore interruptions.
> > 
> > Julian said (
> > http://lkml.kernel.org/r/alpine.LFD.2.00.1310012245020.1782@ja.ssi.bg ):
> > 
> > " Yes, your patch looks ok to me. In the past
> > we used ssleep() but IPVS users were confused why
> > IPVS threads increase the load average. So, we
> > switched to _interruptible calls and later the socket
> > polling was added.  "
> 
> I've done this in the past so that the code sleeps interruptibly
> unless there is a signal pending - which would cause it to return
> early.
> 
>     /* Tell scheduler we are going to sleep... */
>     if (signal_pending(current))
>         /* We don't want waking immediately (again) */
>         sleep_state = TASK_UNINTERRUPTIBLE;
>     else
>         sleep_state = TASK_INTERRUPTIBLE;
>     set_current_state(sleep_state);

If this is for kernel threads, I think you can wipe the pending state;
not entirely sure how signals interact with kthreads; Oleg will know.
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