linux-kernel - Re: [update 3] Re: [RFC][PATCH] PM: Avoid losing wakeup events during suspend

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Date:	Fri, 25 Jun 2010 22:33:32 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Florian Mickler <florian@...kler.org>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Neil Brown <neilb@...e.de>, mark gross <640e9920@...il.com>
Subject: Re: [update 3] Re: [RFC][PATCH] PM: Avoid losing wakeup events during suspend

On Friday, June 25, 2010, Alan Stern wrote:
> On Fri, 25 Jun 2010, Rafael J. Wysocki wrote:
> 
> > So, there it goes.
> > 
> > I decided not to play with memory allocations at this point, because I really
> > don't expect pm_wakeup_event() to be heavily used initially.  If there are more
> > users and it's called more frequently, we can always switch to using a separate
> > slab cache.
> > 
> > Hopefully, I haven't overlooked anything vitally important this time.
> > 
> > Please tell me what you think.
> 
> Obviously comments still need to be added. 

Indeed.

> Beyond that...
> 
> > --- /dev/null
> > +++ linux-2.6/drivers/base/power/wakeup.c
> > @@ -0,0 +1,143 @@
> > +
> > +#include <linux/device.h>
> > +#include <linux/slab.h>
> > +#include <linux/sched.h>
> > +#include <linux/capability.h>
> > +#include <linux/pm.h>
> > +
> > +bool events_check_enabled;
> > +
> > +static unsigned long event_count;
> > +static unsigned long saved_event_count;
> > +static unsigned long events_in_progress;
> > +static spinlock_t events_lock;
> 
> Use static DEFINE_SPINLOCK(events_lock) instead.

Hmm.  I thought that was deprecated.  Never mind.

> > +static DECLARE_WAIT_QUEUE_HEAD(events_wait_queue);
> > +
> > +void pm_wakeup_events_init(void)
> > +{
> > +	spin_lock_init(&events_lock);
> > +}
> 
> Then this routine won't be needed.
> 
> > +unsigned long pm_dev_wakeup_count(struct device *dev)
> > +{
> > +	unsigned long flags;
> > +	unsigned long count;
> > +
> > +	spin_lock_irqsave(&events_lock, flags);
> > +	count = dev->power.wakeup_count;
> > +	spin_unlock_irqrestore(&events_lock, flags);
> > +	return count;
> > +}
> 
> Are the spin_lock calls needed here?  I doubt it.

No, they aren't.  In fact it may be a static inline.

> > --- linux-2.6.orig/kernel/power/power.h
> > +++ linux-2.6/kernel/power/power.h
> > @@ -184,6 +184,15 @@ static inline void suspend_test_finish(c
> >  #ifdef CONFIG_PM_SLEEP
> >  /* kernel/power/main.c */
> >  extern int pm_notifier_call_chain(unsigned long val);
> > +
> > +/* drivers/base/power/wakeup.c */
> > +extern bool events_check_enabled;
> > +
> > +extern void pm_wakeup_events_init(void);
> > +extern bool pm_check_wakeup_events(void);
> > +extern bool pm_check_wakeup_events_final(void);
> > +extern bool pm_get_wakeup_count(unsigned long *count);
> > +extern bool pm_save_wakeup_count(unsigned long count);
> >  #endif
> 
> This is unfortunate.  These declarations belong in a file that can
> also be #included by drivers/base/power/wakeup.c.  Otherwise future
> changes might cause type mismatches the compiler won't be able to
> catch.

You're right.  In that case I think include/linux/suspend.h is the right header
to put them into.

> > @@ -511,18 +513,24 @@ int hibernation_platform_enter(void)
> >  
> >  	local_irq_disable();
> >  	sysdev_suspend(PMSG_HIBERNATE);
> > +	if (!pm_check_wakeup_events()) {
> > +		error = -EAGAIN;
> > +		goto Power_up;
> > +	}
> > +
> >  	hibernation_ops->enter();
> >  	/* We should never get here */
> >  	while (1);
> >  
> > -	/*
> > -	 * We don't need to reenable the nonboot CPUs or resume consoles, since
> > -	 * the system is going to be halted anyway.
> > -	 */
> > + Power_up:
> > +	sysdev_resume();
> > +	local_irq_enable();
> > +	enable_nonboot_cpus();
> > +
> >   Platform_finish:
> >  	hibernation_ops->finish();
> >  
> > -	dpm_suspend_noirq(PMSG_RESTORE);
> > +	dpm_resume_noirq(PMSG_RESTORE);
> 
> Is this a bug fix that crept in along with the other changes?

Yeah.

> > --- linux-2.6.orig/drivers/pci/pci.h
> > +++ linux-2.6/drivers/pci/pci.h
> > @@ -6,6 +6,8 @@
> >  #define PCI_CFG_SPACE_SIZE	256
> >  #define PCI_CFG_SPACE_EXP_SIZE	4096
> >  
> > +#define PCI_WAKEUP_COOLDOWN	100
> 
> This definition can go directly in pci.c, since it isn't used anywhere
> else.

OK

Thanks for the comments,
Rafael
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