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Date: Thu, 1 Jul 2010 01:52:03 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Alan Stern <stern@...land.harvard.edu>
Cc: linux-pm@...ts.linux-foundation.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Neil Brown <neilb@...e.de>,
Matthew Garrett <mjg59@...f.ucam.org>,
mark gross <640e9920@...il.com>,
Arve Hjønnevåg <arve@...roid.com>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Florian Mickler <florian@...kler.org>,
linux-pci@...r.kernel.org, Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [update] Re: [PATCH] PM: Make it possible to avoid wakeup events from being lost
On Wednesday, June 30, 2010, Alan Stern wrote:
> On Wed, 30 Jun 2010, Rafael J. Wysocki wrote:
>
> > > Since there's no longer any way to cancel a call to pm_wakeup_event()
> > > or close the "no suspend" period early, there is no need to use
> > > dynamically-allocated delayed_work structures. You can make do with a
> > > single static timer; always keep it set to expire at the latest time
> > > passed to pm_wakeup_event().
> >
> > The decremenations of events_in_progress wouldn't be balanced with
> > incrementations this way. Or do you have any clever way of dealing with
> > that in mind?
>
> Keep track of the current expiration time in a static variable called
> wakeup_timeout, and use 0 to indicate there is no timeout.
I invented a slightly different version in the meantime, which is appended
as a patch on top of the original one (I don't want to modify the original
patch, since it's been reviewed already by several people and went to my
linux-next branch).
> In pm_wakeup_event() (everything protected by the spinlock):
>
> unsigned long new_timeout = jiffies + msecs_to_jiffies(msecs);
> if (new_timeout == 0)
> new_timeout = 1;
>
> ++event_count;
> if (!wakeup_timeout || time_after(new_timeout, wakeup_timeout)) {
> if (!wakeup_timeout)
> ++events_in_progress;
> wakeup_timeout = new_timeout;
> mod_timer(&wakeup_timer, wakeup_timeout);
> }
>
> In the timer routine:
>
> if (wakeup_timeout && time_before_eq(wakeup_timeout, jiffies)) {
> --events_in_progres;
> wakeup_timeout = 0;
> }
>
---
drivers/base/power/wakeup.c | 47 +++++++++++++++++++++++++++++++++-----------
1 file changed, 36 insertions(+), 11 deletions(-)
Index: linux-2.6/drivers/base/power/wakeup.c
===================================================================
--- linux-2.6.orig/drivers/base/power/wakeup.c
+++ linux-2.6/drivers/base/power/wakeup.c
@@ -9,6 +9,7 @@
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/sched.h>
+#include <linux/ktime.h>
#include <linux/capability.h>
#include <linux/suspend.h>
#include <linux/pm.h>
@@ -28,6 +29,12 @@ static unsigned long events_in_progress;
static DEFINE_SPINLOCK(events_lock);
+static void pm_wakeup_timer_fn(unsigned long data);
+
+static DEFINE_TIMER(events_timer, pm_wakeup_timer_fn, 0, 0);
+static unsigned long events_timer_expires;
+static unsigned long delayed_count;
+
/*
* The functions below use the observation that each wakeup event starts a
* period in which the system should not be suspended. The moment this period
@@ -103,17 +110,23 @@ void pm_relax(void)
}
/**
- * pm_wakeup_work_fn - Deferred closing of a wakeup event.
+ * pm_wakeup_timer_fn - Deferred closing of a wakeup event.
*
* Execute pm_relax() for a wakeup event detected in the past and free the
* work item object used for queuing up the work.
*/
-static void pm_wakeup_work_fn(struct work_struct *work)
+static void pm_wakeup_timer_fn(unsigned long data)
{
- struct delayed_work *dwork = to_delayed_work(work);
+ unsigned long flags;
- pm_relax();
- kfree(dwork);
+ spin_lock_irqsave(&events_lock, flags);
+ if (events_timer_expires && time_after(jiffies, events_timer_expires)) {
+ events_in_progress -= delayed_count;
+ event_count += delayed_count;
+ delayed_count = 0;
+ events_timer_expires = 0;
+ }
+ spin_unlock_irqrestore(&events_lock, flags);
}
/**
@@ -132,19 +145,31 @@ static void pm_wakeup_work_fn(struct wor
void pm_wakeup_event(struct device *dev, unsigned int msec)
{
unsigned long flags;
- struct delayed_work *dwork;
-
- dwork = msec ? kzalloc(sizeof(*dwork), GFP_ATOMIC) : NULL;
spin_lock_irqsave(&events_lock, flags);
if (dev)
dev->power.wakeup_count++;
- if (dwork) {
- INIT_DELAYED_WORK(dwork, pm_wakeup_work_fn);
- schedule_delayed_work(dwork, msecs_to_jiffies(msec));
+ if (msec) {
+ ktime_t kt;
+ struct timespec ts;
+ unsigned long expires;
+
+ kt = ktime_get();
+ kt = ktime_add_ns(kt, msec * NSEC_PER_MSEC);
+ ts = ktime_to_timespec(kt);
+ expires = timespec_to_jiffies(&ts);
+ if (!expires)
+ expires = 1;
+
+ if (!events_timer_expires
+ || time_after(expires, events_timer_expires)) {
+ mod_timer(&events_timer, expires);
+ events_timer_expires = expires;
+ }
events_in_progress++;
+ delayed_count++;
} else {
event_count++;
}
--
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