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    SubjectRe: [PATCH 3/3] PM / Sleep: Make __pm_stay_awake() delete wakeup source timers
    Date
    On Thursday, February 16, 2012, Arve Hjønnevåg wrote:
    > 2012/2/15 Rafael J. Wysocki <rjw@sisk.pl>:
    > ...
    > > --- linux.orig/drivers/base/power/wakeup.c
    > > +++ linux/drivers/base/power/wakeup.c
    > > @@ -365,9 +365,15 @@ void __pm_stay_awake(struct wakeup_sourc
    > > return;
    > >
    > > spin_lock_irqsave(&ws->lock, flags);
    > > +
    > > + del_timer(&ws->timer);
    > > + ws->timer_expires = 0;
    >
    > timer_expires gets overwritten in wakeup_source_activate,

    I actually don't remember why it does that and with the $subject changes
    it's just pointless.

    > so __pm_relax followed by __pm_stay_awake is still not safe.

    Yes, I overlooked that timer_expires modification. Updated patch follows.

    > ...
    > > @@ -529,8 +535,12 @@ void __pm_wakeup_event(struct wakeup_sou
    > > spin_lock_irqsave(&ws->lock, flags);
    > >
    > > ws->event_count++;
    > > - if (!ws->active)
    > > + if (ws->active) {
    > > + if (!ws->timer_expires)
    > > + goto unlock;
    > > + } else {
    > > wakeup_source_activate(ws);
    > > + }
    > >
    > > if (!msec) {
    > > wakeup_source_deactivate(ws);
    > >
    >
    > I suggest dropping this and adding:

    Well, what exactly would you like to drop? The above proposed changes I guess?

    > - if (time_after(expires, ws->timer_expires)) {
    > + if (!ws->timer_expires || time_after(expires, ws->timer_expires)) {

    I've tried to follow your suggestion, so that __pm_wakeup_event() always
    sets the timer, if msec is positive, or deactivates the wakeup source, if
    msec is 0. Please let me know if that's what you wanted. :-)

    Thanks,
    Rafael


    ---
    From: Rafael J. Wysocki <rjw@sisk.pl>
    Subject: PM / Sleep: Make __pm_stay_awake() delete wakeup source timers

    If __pm_stay_awake() is called after __pm_wakeup_event() for the same
    wakep source object before its timer expires, it won't cancel the
    timer, so the wakeup source will be deactivated from the timer
    function as scheduled by __pm_wakeup_event(). In that case
    __pm_stay_awake() doesn't have any effect beyond incrementing
    the wakeup source's event_count field, although it should cancel
    the timer and make the wakeup source stay active until __pm_relax()
    is called for it.

    To fix this problem make __pm_stay_awake() delete the wakeup source's
    timer and ensure that it won't be deactivated from the timer funtion
    afterwards by clearing its timer_expires field.

    Reported-by: Arve Hjønnevåg <arve@android.com>
    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    ---
    drivers/base/power/wakeup.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    Index: linux/drivers/base/power/wakeup.c
    ===================================================================
    --- linux.orig/drivers/base/power/wakeup.c
    +++ linux/drivers/base/power/wakeup.c
    @@ -344,7 +344,6 @@ static void wakeup_source_activate(struc
    {
    ws->active = true;
    ws->active_count++;
    - ws->timer_expires = jiffies;
    ws->last_time = ktime_get();

    /* Increment the counter of events in progress. */
    @@ -365,9 +364,14 @@ void __pm_stay_awake(struct wakeup_sourc
    return;

    spin_lock_irqsave(&ws->lock, flags);
    +
    ws->event_count++;
    if (!ws->active)
    wakeup_source_activate(ws);
    +
    + del_timer(&ws->timer);
    + ws->timer_expires = 0;
    +
    spin_unlock_irqrestore(&ws->lock, flags);
    }
    EXPORT_SYMBOL_GPL(__pm_stay_awake);
    @@ -541,7 +545,7 @@ void __pm_wakeup_event(struct wakeup_sou
    if (!expires)
    expires = 1;

    - if (time_after(expires, ws->timer_expires)) {
    + if (!ws->timer_expires || time_after(expires, ws->timer_expires)) {
    mod_timer(&ws->timer, expires);
    ws->timer_expires = expires;
    }
    --
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