[v1] PM: runtime: Update device status before letting suppliers suspend
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Message ID 1930477.9OOUKYNkGr@kreacher
State New, archived
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  • [v1] PM: runtime: Update device status before letting suppliers suspend
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Commit Message

Rafael J. Wysocki Feb. 24, 2021, 5:53 p.m. UTC
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Because the PM-runtime status of the device is not updated in
__rpm_callback(), attempts to suspend the suppliers of the given
device triggered by rpm_put_suppliers() called by it may fail.

Fix this by making __rpm_callback() update the device's status to
RPM_SUSPENDED before calling rpm_put_suppliers() if the current
status of the device is RPM_SUSPENDING and the callback just invoked
by it has returned 0 (success).

While at it, modify the code in __rpm_callback() to always check
the device's PM-runtime status under its PM lock.

Link: https://lore.kernel.org/linux-pm/CAPDyKFqm06KDw_p8WXsM4dijDbho4bb6T4k50UqqvR1_COsp8g@mail.gmail.com/
Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
Reported-by: elaine.zhang <zhangqing@rock-chips.com>
Diagnosed-by: Ulf Hansson <ulf.hansson@linaro.org> 
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

This is different from the previously posted tentative patch, please retest.

---
 drivers/base/power/runtime.c |   61 +++++++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 25 deletions(-)

Comments

Elaine Zhang Feb. 25, 2021, 1:26 a.m. UTC | #1
Hi, Rafael:

在 2021/2/25 上午1:53, Rafael J. Wysocki 写道:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Because the PM-runtime status of the device is not updated in
> __rpm_callback(), attempts to suspend the suppliers of the given
> device triggered by rpm_put_suppliers() called by it may fail.
>
> Fix this by making __rpm_callback() update the device's status to
> RPM_SUSPENDED before calling rpm_put_suppliers() if the current
> status of the device is RPM_SUSPENDING and the callback just invoked
> by it has returned 0 (success).
>
> While at it, modify the code in __rpm_callback() to always check
> the device's PM-runtime status under its PM lock.
>
> Link: https://lore.kernel.org/linux-pm/CAPDyKFqm06KDw_p8WXsM4dijDbho4bb6T4k50UqqvR1_COsp8g@mail.gmail.com/
> Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
> Reported-by: elaine.zhang <zhangqing@rock-chips.com>
> Diagnosed-by: Ulf Hansson <ulf.hansson@linaro.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> This is different from the previously posted tentative patch, please retest.
>
> ---
>   drivers/base/power/runtime.c |   61 +++++++++++++++++++++++++------------------
>   1 file changed, 36 insertions(+), 25 deletions(-)
>
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -325,22 +325,21 @@ static void rpm_put_suppliers(struct dev
>   static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
>   	__releases(&dev->power.lock) __acquires(&dev->power.lock)
>   {
> -	int retval, idx;
>   	bool use_links = dev->power.links_count > 0;
> +	int retval, idx;
> +	bool get, put;
>   
>   	if (dev->power.irq_safe) {
>   		spin_unlock(&dev->power.lock);
> +	} else if (!use_links) {
> +		spin_unlock_irq(&dev->power.lock);
>   	} else {
> +		get = dev->power.runtime_status == RPM_RESUMING;
> +
>   		spin_unlock_irq(&dev->power.lock);
>   
> -		/*
> -		 * Resume suppliers if necessary.
> -		 *
> -		 * The device's runtime PM status cannot change until this
> -		 * routine returns, so it is safe to read the status outside of
> -		 * the lock.
> -		 */
> -		if (use_links && dev->power.runtime_status == RPM_RESUMING) {
> +		/* Resume suppliers if necessary. */
> +		if (get) {
>   			idx = device_links_read_lock();
>   
>   			retval = rpm_get_suppliers(dev);
> @@ -355,24 +354,36 @@ static int __rpm_callback(int (*cb)(stru
>   
>   	if (dev->power.irq_safe) {
>   		spin_lock(&dev->power.lock);
> -	} else {
> -		/*
> -		 * If the device is suspending and the callback has returned
> -		 * success, drop the usage counters of the suppliers that have
> -		 * been reference counted on its resume.
> -		 *
> -		 * Do that if resume fails too.
> -		 */
> -		if (use_links
> -		    && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
> -		    || (dev->power.runtime_status == RPM_RESUMING && retval))) {
> -			idx = device_links_read_lock();
> +		return retval;
> +	}
>   
> - fail:
> -			rpm_put_suppliers(dev);
> +	spin_lock_irq(&dev->power.lock);
>   
> -			device_links_read_unlock(idx);
> -		}
> +	if (!use_links)
> +		return retval;
> +
> +	/*
> +	 * If the device is suspending and the callback has returned success,
> +	 * drop the usage counters of the suppliers that have been reference
> +	 * counted on its resume.
> +	 *
> +	 * Do that if the resume fails too.
> +	 */
> +	put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
> +	if (put)
> +		__update_runtime_status(dev, RPM_SUSPENDED);
> +	else
> +		put = get && retval;
> +
> +	if (put) {
> +		spin_unlock_irq(&dev->power.lock);
> +
> +		idx = device_links_read_lock();
> +
> +fail:
> +		rpm_put_suppliers(dev);
> +
> +		device_links_read_unlock(idx);
>   
>   		spin_lock_irq(&dev->power.lock);
>   	}
drivers/base/power/runtime.c: In function '__rpm_callback':
drivers/base/power/runtime.c:355:13: warning: 'get' may be used 
uninitialized in this function [-Wmaybe-uninitialized]
error, forbidden warning:runtime.c:355
    put = get && retval;

There is a compilation error. I change it as:

put = dev->power.runtime_status == RPM_SUSPENDING && retval;

And test works well.Please check it.

>
>
>
>
>
>
Rafael J. Wysocki Feb. 25, 2021, 12:06 p.m. UTC | #2
On Thu, Feb 25, 2021 at 2:32 AM elaine.zhang <zhangqing@rock-chips.com> wrote:
>
> Hi, Rafael:
>
> 在 2021/2/25 上午1:53, Rafael J. Wysocki 写道:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Because the PM-runtime status of the device is not updated in
> > __rpm_callback(), attempts to suspend the suppliers of the given
> > device triggered by rpm_put_suppliers() called by it may fail.
> >
> > Fix this by making __rpm_callback() update the device's status to
> > RPM_SUSPENDED before calling rpm_put_suppliers() if the current
> > status of the device is RPM_SUSPENDING and the callback just invoked
> > by it has returned 0 (success).
> >
> > While at it, modify the code in __rpm_callback() to always check
> > the device's PM-runtime status under its PM lock.
> >
> > Link: https://lore.kernel.org/linux-pm/CAPDyKFqm06KDw_p8WXsM4dijDbho4bb6T4k50UqqvR1_COsp8g@mail.gmail.com/
> > Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
> > Reported-by: elaine.zhang <zhangqing@rock-chips.com>
> > Diagnosed-by: Ulf Hansson <ulf.hansson@linaro.org>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >
> > This is different from the previously posted tentative patch, please retest.
> >
> > ---
> >   drivers/base/power/runtime.c |   61 +++++++++++++++++++++++++------------------
> >   1 file changed, 36 insertions(+), 25 deletions(-)
> >
> > Index: linux-pm/drivers/base/power/runtime.c
> > ===================================================================
> > --- linux-pm.orig/drivers/base/power/runtime.c
> > +++ linux-pm/drivers/base/power/runtime.c
> > @@ -325,22 +325,21 @@ static void rpm_put_suppliers(struct dev
> >   static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
> >       __releases(&dev->power.lock) __acquires(&dev->power.lock)
> >   {
> > -     int retval, idx;
> >       bool use_links = dev->power.links_count > 0;
> > +     int retval, idx;
> > +     bool get, put;
> >
> >       if (dev->power.irq_safe) {
> >               spin_unlock(&dev->power.lock);
> > +     } else if (!use_links) {
> > +             spin_unlock_irq(&dev->power.lock);
> >       } else {
> > +             get = dev->power.runtime_status == RPM_RESUMING;
> > +
> >               spin_unlock_irq(&dev->power.lock);
> >
> > -             /*
> > -              * Resume suppliers if necessary.
> > -              *
> > -              * The device's runtime PM status cannot change until this
> > -              * routine returns, so it is safe to read the status outside of
> > -              * the lock.
> > -              */
> > -             if (use_links && dev->power.runtime_status == RPM_RESUMING) {
> > +             /* Resume suppliers if necessary. */
> > +             if (get) {
> >                       idx = device_links_read_lock();
> >
> >                       retval = rpm_get_suppliers(dev);
> > @@ -355,24 +354,36 @@ static int __rpm_callback(int (*cb)(stru
> >
> >       if (dev->power.irq_safe) {
> >               spin_lock(&dev->power.lock);
> > -     } else {
> > -             /*
> > -              * If the device is suspending and the callback has returned
> > -              * success, drop the usage counters of the suppliers that have
> > -              * been reference counted on its resume.
> > -              *
> > -              * Do that if resume fails too.
> > -              */
> > -             if (use_links
> > -                 && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
> > -                 || (dev->power.runtime_status == RPM_RESUMING && retval))) {
> > -                     idx = device_links_read_lock();
> > +             return retval;
> > +     }
> >
> > - fail:
> > -                     rpm_put_suppliers(dev);
> > +     spin_lock_irq(&dev->power.lock);
> >
> > -                     device_links_read_unlock(idx);
> > -             }
> > +     if (!use_links)
> > +             return retval;
> > +
> > +     /*
> > +      * If the device is suspending and the callback has returned success,
> > +      * drop the usage counters of the suppliers that have been reference
> > +      * counted on its resume.
> > +      *
> > +      * Do that if the resume fails too.
> > +      */
> > +     put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
> > +     if (put)
> > +             __update_runtime_status(dev, RPM_SUSPENDED);
> > +     else
> > +             put = get && retval;
> > +
> > +     if (put) {
> > +             spin_unlock_irq(&dev->power.lock);
> > +
> > +             idx = device_links_read_lock();
> > +
> > +fail:
> > +             rpm_put_suppliers(dev);
> > +
> > +             device_links_read_unlock(idx);
> >
> >               spin_lock_irq(&dev->power.lock);
> >       }
> drivers/base/power/runtime.c: In function '__rpm_callback':
> drivers/base/power/runtime.c:355:13: warning: 'get' may be used
> uninitialized in this function [-Wmaybe-uninitialized]
> error, forbidden warning:runtime.c:355

This really is a false-positive, because in fact the "get" variable
cannot be uninitialized at this point.

>     put = get && retval;
>
> There is a compilation error. I change it as:
>
> put = dev->power.runtime_status == RPM_SUSPENDING && retval;

I prefer to initialize "get" to false (even though that is not
strictly necessary).

> And test works well.Please check it.

OK, thanks for testing!

I will send an updated patch later today.

Patch
diff mbox series

Index: linux-pm/drivers/base/power/runtime.c
===================================================================
--- linux-pm.orig/drivers/base/power/runtime.c
+++ linux-pm/drivers/base/power/runtime.c
@@ -325,22 +325,21 @@  static void rpm_put_suppliers(struct dev
 static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
 	__releases(&dev->power.lock) __acquires(&dev->power.lock)
 {
-	int retval, idx;
 	bool use_links = dev->power.links_count > 0;
+	int retval, idx;
+	bool get, put;
 
 	if (dev->power.irq_safe) {
 		spin_unlock(&dev->power.lock);
+	} else if (!use_links) {
+		spin_unlock_irq(&dev->power.lock);
 	} else {
+		get = dev->power.runtime_status == RPM_RESUMING;
+
 		spin_unlock_irq(&dev->power.lock);
 
-		/*
-		 * Resume suppliers if necessary.
-		 *
-		 * The device's runtime PM status cannot change until this
-		 * routine returns, so it is safe to read the status outside of
-		 * the lock.
-		 */
-		if (use_links && dev->power.runtime_status == RPM_RESUMING) {
+		/* Resume suppliers if necessary. */
+		if (get) {
 			idx = device_links_read_lock();
 
 			retval = rpm_get_suppliers(dev);
@@ -355,24 +354,36 @@  static int __rpm_callback(int (*cb)(stru
 
 	if (dev->power.irq_safe) {
 		spin_lock(&dev->power.lock);
-	} else {
-		/*
-		 * If the device is suspending and the callback has returned
-		 * success, drop the usage counters of the suppliers that have
-		 * been reference counted on its resume.
-		 *
-		 * Do that if resume fails too.
-		 */
-		if (use_links
-		    && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
-		    || (dev->power.runtime_status == RPM_RESUMING && retval))) {
-			idx = device_links_read_lock();
+		return retval;
+	}
 
- fail:
-			rpm_put_suppliers(dev);
+	spin_lock_irq(&dev->power.lock);
 
-			device_links_read_unlock(idx);
-		}
+	if (!use_links)
+		return retval;
+
+	/*
+	 * If the device is suspending and the callback has returned success,
+	 * drop the usage counters of the suppliers that have been reference
+	 * counted on its resume.
+	 *
+	 * Do that if the resume fails too.
+	 */
+	put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
+	if (put)
+		__update_runtime_status(dev, RPM_SUSPENDED);
+	else
+		put = get && retval;
+
+	if (put) {
+		spin_unlock_irq(&dev->power.lock);
+
+		idx = device_links_read_lock();
+
+fail:
+		rpm_put_suppliers(dev);
+
+		device_links_read_unlock(idx);
 
 		spin_lock_irq(&dev->power.lock);
 	}