2021-02-24 17:58:28

by Rafael J. Wysocki

[permalink] [raw]
Subject: [PATCH v1] PM: runtime: Update device status before letting suppliers suspend

From: Rafael J. Wysocki <[email protected]>

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 <[email protected]>
Diagnosed-by: Ulf Hansson <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
---

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);
}




2021-02-25 08:34:37

by zhangqing

[permalink] [raw]
Subject: Re: [PATCH v1] PM: runtime: Update device status before letting suppliers suspend

Hi, Rafael:

在 2021/2/25 上午1:53, Rafael J. Wysocki 写道:
> From: Rafael J. Wysocki <[email protected]>
>
> 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 <[email protected]>
> Diagnosed-by: Ulf Hansson <[email protected]>
> Signed-off-by: Rafael J. Wysocki <[email protected]>
> ---
>
> 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.

>
>
>
>
>
>


2021-02-25 12:10:43

by Rafael J. Wysocki

[permalink] [raw]
Subject: Re: [PATCH v1] PM: runtime: Update device status before letting suppliers suspend

On Thu, Feb 25, 2021 at 2:32 AM elaine.zhang <[email protected]> wrote:
>
> Hi, Rafael:
>
> 在 2021/2/25 上午1:53, Rafael J. Wysocki 写道:
> > From: Rafael J. Wysocki <[email protected]>
> >
> > 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 <[email protected]>
> > Diagnosed-by: Ulf Hansson <[email protected]>
> > Signed-off-by: Rafael J. Wysocki <[email protected]>
> > ---
> >
> > 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.