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    Subject[PATCH 1/6] [RFC] suspend: Block suspend when wakeups are in-progress
    Date
    With the current pm_stay_awake/pm_relax api, reads to
    /sys/power/wakeup_count will block when pm_stay_awake() has been
    called. Then once pm_relax() returns, the read will unblock and return
    the wakeup_count value. This value can be echo'ed back into wakeup_count,
    and if no other wakeup events have occured, the system can be suspended
    by calling "echo mem > /sys/power/state".

    This method is somewhat advisory, as if a wakeup event has occured
    between the reading of /sys/power/wakeup_count and the attempt to suspend,
    that attempt to suspend will fail. However, if a second attmept to suspend
    is tried, without checking /sys/power/wakeup_count, the suspend will
    succeed.

    Similarly, if pm_stay_awake() has been called, and then a suspend is
    attepted wihtout checking /sys/power/wakeup_count, the suspend will
    succeed, despite the pm_relax() call not having been made.

    This patch tries to make the pm_stay_awake() call a bit more enforcing,
    such that any attempt to suspend that occurs while a wakeup is in progress
    will fail. Once the matching pm_relax() has been called, suspend will
    succeed.

    This does not change the blocking behavior of /sys/power/wakeup_count,
    or the suspend failure if a stale wakeup count has been echo'ed into
    the /sys/power/wakeup_count.

    Also modified the hibernate path in the same way.

    CC: Rafael J. Wysocki <rjw@sisk.pl>
    CC: arve@android.com
    CC: markgross@thegnar.org
    CC: Alan Stern <stern@rowland.harvard.edu>
    CC: amit.kucheria@linaro.org
    CC: farrowg@sg.ibm.com
    CC: Dmitry Fink (Palm GBU) <Dmitry.Fink@palm.com>
    CC: linux-pm@lists.linux-foundation.org
    CC: khilman@ti.com
    CC: Magnus Damm <damm@opensource.se>
    CC: mjg@redhat.com
    CC: peterz@infradead.org
    Signed-off-by: John Stultz <john.stultz@linaro.org>
    ---
    drivers/base/power/wakeup.c | 13 +++++++++++++
    include/linux/suspend.h | 3 +++
    kernel/power/hibernate.c | 5 +++++
    kernel/power/suspend.c | 5 +++++
    4 files changed, 26 insertions(+), 0 deletions(-)

    diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
    index 84f7c7d..0722873 100644
    --- a/drivers/base/power/wakeup.c
    +++ b/drivers/base/power/wakeup.c
    @@ -580,6 +580,19 @@ static void pm_wakeup_update_hit_counts(void)
    rcu_read_unlock();
    }

    +
    +bool pm_wakeup_in_progress(void)
    +{
    + unsigned int cnt, inpr;
    + unsigned long flags;
    +
    + spin_lock_irqsave(&events_lock, flags);
    + split_counters(&cnt, &inpr);
    + spin_unlock_irqrestore(&events_lock, flags);
    +
    + return (inpr != 0);
    +}
    +
    /**
    * pm_wakeup_pending - Check if power transition in progress should be aborted.
    *
    diff --git a/include/linux/suspend.h b/include/linux/suspend.h
    index 6bbcef2..c9403a1 100644
    --- a/include/linux/suspend.h
    +++ b/include/linux/suspend.h
    @@ -294,6 +294,7 @@ extern int unregister_pm_notifier(struct notifier_block *nb);
    extern bool events_check_enabled;

    extern bool pm_wakeup_pending(void);
    +extern bool pm_wakeup_in_progress(void);
    extern bool pm_get_wakeup_count(unsigned int *count);
    extern bool pm_save_wakeup_count(unsigned int count);
    #else /* !CONFIG_PM_SLEEP */
    @@ -311,6 +312,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
    #define pm_notifier(fn, pri) do { (void)(fn); } while (0)

    static inline bool pm_wakeup_pending(void) { return false; }
    +static inline bool pm_wakeup_in_progress(void) { return false; }
    +
    #endif /* !CONFIG_PM_SLEEP */

    extern struct mutex pm_mutex;
    diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
    index 8f7b1db..22dc22c 100644
    --- a/kernel/power/hibernate.c
    +++ b/kernel/power/hibernate.c
    @@ -611,6 +611,11 @@ int hibernate(void)
    goto Unlock;
    }

    + if (pm_wakeup_in_progress()) {
    + error = -EBUSY;
    + goto Unlock;
    + }
    +
    pm_prepare_console();
    error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
    if (error)
    diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
    index b6b71ad..b2dba52 100644
    --- a/kernel/power/suspend.c
    +++ b/kernel/power/suspend.c
    @@ -281,6 +281,11 @@ int enter_state(suspend_state_t state)
    if (!mutex_trylock(&pm_mutex))
    return -EBUSY;

    + if (pm_wakeup_in_progress()) {
    + error = -EBUSY;
    + goto Unlock;
    + }
    +
    printk(KERN_INFO "PM: Syncing filesystems ... ");
    sys_sync();
    printk("done.\n");
    --
    1.7.3.2.146.gca209


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