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Subject[PATCH 5.10 011/157] Revert "PM: runtime: Update device status before letting suppliers suspend"
Date
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.com/
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);
}

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