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PM: runtime: Fix race getting/putting suppliers at probe 

pm_runtime_put_suppliers() must not decrement rpm_active unless the
consumer is suspended. That is because, otherwise, it could suspend
suppliers for an active consumer.

That can happen as follows:

 static int driver_probe_device(struct device_driver *drv, struct device *dev)
 {
	int ret = 0;

	if (!device_is_registered(dev))
		return -ENODEV;

	dev->can_match = true;
	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
		 drv->bus->name, __func__, dev_name(dev), drv->name);

	pm_runtime_get_suppliers(dev);
	if (dev->parent)
		pm_runtime_get_sync(dev->parent);

 At this point, dev can runtime suspend so rpm_put_suppliers() can run,
 rpm_active becomes 1 (the lowest value).

	pm_runtime_barrier(dev);
	if (initcall_debug)
		ret = really_probe_debug(dev, drv);
	else
		ret = really_probe(dev, drv);

 Probe callback can have runtime resumed dev, and then runtime put
 so dev is awaiting autosuspend, but rpm_active is 2.

	pm_request_idle(dev);

	if (dev->parent)
		pm_runtime_put(dev->parent);

	pm_runtime_put_suppliers(dev);

 Now pm_runtime_put_suppliers() will put the supplier
 i.e. rpm_active 2 -> 1, but consumer can still be active.

	return ret;
 }

Fix by checking the runtime status. For any status other than
RPM_SUSPENDED, rpm_active can be considered to be "owned" by
rpm_[get/put]_suppliers() and pm_runtime_put_suppliers() need do nothing.

Reported-by: Asutosh Das <asutoshd@codeaurora.org>
Fixes: 4c06c4e6cf ("driver core: Fix possible supplier PM-usage counter imbalance")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: 5.1+ <stable@vger.kernel.org> # 5.1+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Adrian Hunter 2021-03-26 12:56:19 +02:00 committed by Rafael J. Wysocki
parent c0c33442f7
commit 9dfacc54a8
1 changed files with 7 additions and 1 deletions
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8
drivers/base/power/runtime.c
View File

@ -1704,6 +1704,8 @@ void pm_runtime_get_suppliers(struct device *dev)
void pm_runtime_put_suppliers(struct device *dev)
{
struct device_link *link;
unsigned long flags;
bool put;
int idx;
idx = device_links_read_lock();
@ -1712,7 +1714,11 @@ void pm_runtime_put_suppliers(struct device *dev)
device_links_read_lock_held())
if (link->supplier_preactivated) {
link->supplier_preactivated = false;
if (refcount_dec_not_one(&link->rpm_active))
spin_lock_irqsave(&dev->power.lock, flags);
put = pm_runtime_status_suspended(dev) &&
refcount_dec_not_one(&link->rpm_active);
spin_unlock_irqrestore(&dev->power.lock, flags);
if (put)
pm_runtime_put(link->supplier);
}