netdev - RE: [PATCH] ipvs: Remove unused variable ret from sync_thread

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Date:	Tue, 12 Nov 2013 14:21:39 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Peter Zijlstra" <peterz@...radead.org>,
	"Geert Uytterhoeven" <geert@...ux-m68k.org>
Cc:	"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()

> > @@ -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);

Shame there isn't a process flag to indicate that the process
will sleep uninterruptibly and that it doesn't matter.
So don't count to the load average and don't emit a warning
if it has been sleeping for a long time.

	David



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