linux-kernel - Re: [PATCH 1/8] PM: Add suspend block api.

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Message-Id: <201005062128.31068.rjw@sisk.pl>
Date:	Thu, 6 May 2010 21:28:30 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Randy Dunlap <rdunlap@...otime.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Nigel Cunningham <nigel@...onice.net>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Ming Lei <tom.leiming@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/8] PM: Add suspend block api.

On Thursday 06 May 2010, Alan Stern wrote:
> On Tue, 27 Apr 2010, [UTF-8] Arve HjÃ¸nnevÃ¥g wrote:
> 
> > +static void suspend_worker(struct work_struct *work)
> > +{
> > +	int ret;
> > +	int entry_event_num;
> > +
> > +	enable_suspend_blockers = true;
> > +	while (!suspend_is_blocked()) {
> > +		entry_event_num = current_event_num;
> > +
> > +		if (debug_mask & DEBUG_SUSPEND)
> > +			pr_info("suspend: enter suspend\n");
> > +
> > +		ret = pm_suspend(requested_suspend_state);
> > +
> > +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> > +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> > +
> > +		if (current_event_num == entry_event_num)
> > +			pr_info("suspend: pm_suspend returned with no event\n");
> > +	}
> > +	enable_suspend_blockers = false;
> > +}
> 
> Here's a completely new issue.  When using opportunistic suspends on an
> SMP system, it could happen that the system gets a wakeup event and
> this routine starts running again before the event's IRQ handler has
> finished (or has enabled a suspend blocker).  The system would 
> re-suspend too soon.

This routine will be run from a freezable workqueue.

Rafael
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