[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Pine.LNX.4.44L0.0710271516570.30287-100000@netrider.rowland.org>
Date: Sat, 27 Oct 2007 15:17:55 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Maxim Levitsky <maximlevitsky@...il.com>
cc: linux-kernel@...r.kernel.org, <netdev@...r.kernel.org>,
<linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] QUESTION: How to fix race between .suspend routine
and watchdog timer
On Fri, 26 Oct 2007, Maxim Levitsky wrote:
> > > Looking through the dmfe code, I noticed yet another possible race.
> > > A race between the .suspend, and a timer that serves both as a watchdog, and link state detector.
> > > Again I need to prevent it from running during the suspend/resume, but how?
> > >
> > > I can use del_timer in .suspend, and mod_timer in .resume, but that doesn't protect against
> > > race with already running timer.
> > > I can use del_timer_sync, but it states that it is useless if timer re-enables itself, and I agree with that.
> > > In dmfe case the timer does re-enable itself.
> >
> > That comment isn't right. del_timer_sync works perfectly well even if
> > the timer routine re-enables itself, provided it stops doing so after a
> > small number of iterations.
> Thanks for the info. but....
> Due to the "don't access the hardware, while powered-off" rule, I must know that the timer isn't running.
> and won't be.
> So what function to use (if possible) to be sure that the timer won't run anymore?
> (Taking in the account the fact that it re-enables itself)
Use del_timer_sync(). It guarantees that when it returns, the timer
will be stopped and the timer routine will no longer be running on any
CPU.
Alan Stern
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists