From: Rafael J. Wysocki rafael.j.wysocki@intel.com
commit 0cab893f409c53634d0d818fa414641cbcdb0dab upstream.
Revert commit 44cc89f76464 ("PM: runtime: Update device status before letting suppliers suspend") that introduced a race condition into __rpm_callback() which allowed a concurrent rpm_resume() to run and resume the device prematurely after its status had been changed to RPM_SUSPENDED by __rpm_callback().
Fixes: 44cc89f76464 ("PM: runtime: Update device status before letting suppliers suspend") Link: https://lore.kernel.org/linux-pm/24dfb6fc-5d54-6ee2-9195-26428b7ecf8a@intel.... Reported-by: Adrian Hunter adrian.hunter@intel.com Cc: 4.10+ stable@vger.kernel.org # 4.10+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/base/power/runtime.c | 62 +++++++++++++++++-------------------------- 1 file changed, 25 insertions(+), 37 deletions(-)
--- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -325,22 +325,22 @@ 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) { - bool use_links = dev->power.links_count > 0; - bool get = false; int retval, idx; - bool put; + bool use_links = dev->power.links_count > 0;
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. */ - if (get) { + /* + * 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) { idx = device_links_read_lock();
retval = rpm_get_suppliers(dev); @@ -355,36 +355,24 @@ static int __rpm_callback(int (*cb)(stru
if (dev->power.irq_safe) { spin_lock(&dev->power.lock); - return retval; - } - - spin_lock_irq(&dev->power.lock); - - 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(); + } 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();
-fail: - rpm_put_suppliers(dev); + fail: + rpm_put_suppliers(dev);
- device_links_read_unlock(idx); + device_links_read_unlock(idx); + }
spin_lock_irq(&dev->power.lock); }