linux-kernel - Re: PM / wakeirq: Convert to SRCU

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Date:   Sun, 25 Jun 2017 07:45:59 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Brian Norris <briannorris@...omium.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-rockchip@...ts.infradead.org,
        Julia Cartwright <julia@...com>,
        LKML <linux-kernel@...r.kernel.org>, linux-gpio@...r.kernel.org,
        John Keeping <john@...anate.com>, linux-pm@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Lindgren <tony@...mide.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: PM / wakeirq: Convert to SRCU

On Sun, Jun 25, 2017 at 11:11:57AM +0200, Thomas Gleixner wrote:
> On Sat, 24 Jun 2017, Paul E. McKenney wrote:
> > On Sat, Jun 24, 2017 at 11:56:11AM +0200, Thomas Gleixner wrote:
> > >  static DECLARE_WAIT_QUEUE_HEAD(wakeup_count_wait_queue);
> > > 
> > > +static struct srcu_struct wakeup_srcu;
> > 
> > I suggest this to avoid the need for boot-time init_srcu_struct():
> > 
> > DEFINE_STATIC_SRCU(wakeup_srcu);
> 
> Now I know why I had this nagging feeling, that should stay away from
> computers yesterday morning.....

Believe me, I know that feeling well!

> > >  static struct wakeup_source deleted_ws = {
> > >  	.name = "deleted",
> > >  	.lock =  __SPIN_LOCK_UNLOCKED(deleted_ws.lock),
> > > @@ -198,7 +200,7 @@ void wakeup_source_remove(struct wakeup_
> > >  	spin_lock_irqsave(&events_lock, flags);
> > >  	list_del_rcu(&ws->entry);
> > >  	spin_unlock_irqrestore(&events_lock, flags);
> > > -	synchronize_rcu();
> > > +	synchronize_srcu(&wakeup_srcu);
> > >  }
> > >  EXPORT_SYMBOL_GPL(wakeup_source_remove);
> > 
> > The uses of RCU in device_wakeup_arm_wake_irqs() and
> > device_wakeup_disarm_wake_irqs() are unrelated and thus do not
> > need to be converted?  Or am I looking at the wrong version of
> > the kernel?  (Looking at f65013d655ac ("Merge branch 'for-linus' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
> > in Linus's tree.)
> 
> No, you are looking at the result of heat induced brain melt. Will send a
> proper one soon.

And if anything, I know that feeling even better.  Looking forward to
seeing the new patch.

							Thanx, Paul