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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-02-12 13:08:10 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-13 09:09:57 +0100
commit4c06c4e6cf63d7f3d5dfe62593a073253d750a59 (patch)
tree3c3d0acadfb52eb4a025aba277c1593a5175b885 /drivers/base/power
parentc1567f813a9992a64f8d0f6cfb912c3922812c35 (diff)
driver core: Fix possible supplier PM-usage counter imbalance
If a stateless device link to a certain supplier with DL_FLAG_PM_RUNTIME set in the flags is added and then removed by the consumer driver's probe callback, the supplier's PM-runtime usage counter will be nonzero after that which effectively causes the supplier to remain "always on" going forward. Namely, device_link_add() called to add the link invokes device_link_rpm_prepare() which notices that the consumer driver is probing, so it increments the supplier's PM-runtime usage counter with the assumption that the link will stay around until pm_runtime_put_suppliers() is called by driver_probe_device(), but if the link goes away before that point, the supplier's PM-runtime usage counter will remain nonzero. To prevent that from happening, first rework pm_runtime_get_suppliers() and pm_runtime_put_suppliers() to use the rpm_active refounts of device links and make the latter only drop rpm_active and the supplier's PM-runtime usage counter for each link by one, unless rpm_active is one already for it. Next, modify device_link_add() to bump up the new link's rpm_active refcount and the suppliers PM-runtime usage counter by two, to prevent pm_runtime_put_suppliers(), if it is called subsequently, from suspending the supplier prematurely (in case its PM-runtime usage counter goes down to 0 in there). Due to the way rpm_put_suppliers() works, this change does not affect runtime suspend of the consumer ends of new device links (or, generally, device links for which DL_FLAG_PM_RUNTIME has just been set). Fixes: e2f3cd831a28 ("driver core: Fix handling of runtime PM flags in device_link_add()") Reported-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Tested-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/base/power')
-rw-r--r--drivers/base/power/runtime.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index af23eb327f57..6b8aa6bed064 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1625,8 +1625,10 @@ void pm_runtime_get_suppliers(struct device *dev)
idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
- if (link->flags & DL_FLAG_PM_RUNTIME)
+ if (link->flags & DL_FLAG_PM_RUNTIME) {
+ refcount_inc(&link->rpm_active);
pm_runtime_get_sync(link->supplier);
+ }
device_links_read_unlock(idx);
}
@@ -1643,7 +1645,8 @@ void pm_runtime_put_suppliers(struct device *dev)
idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
- if (link->flags & DL_FLAG_PM_RUNTIME)
+ if (link->flags & DL_FLAG_PM_RUNTIME &&
+ refcount_dec_not_one(&link->rpm_active))
pm_runtime_put(link->supplier);
device_links_read_unlock(idx);
@@ -1656,6 +1659,26 @@ void pm_runtime_new_link(struct device *dev)
spin_unlock_irq(&dev->power.lock);
}
+/**
+ * pm_runtime_active_link - Set up new device link as active for PM-runtime.
+ * @link: Device link to be set up as active.
+ * @supplier: Supplier end of the link.
+ *
+ * Add 2 to the rpm_active refcount of @link and increment the PM-runtime
+ * usage counter of @supplier once more in case the link is being added while
+ * the consumer driver is probing and pm_runtime_put_suppliers() will be called
+ * subsequently.
+ *
+ * Note that this doesn't prevent rpm_put_suppliers() from decreasing the link's
+ * rpm_active refcount down to one, so runtime suspend of the consumer end of
+ * @link is not affected.
+ */
+void pm_runtime_active_link(struct device_link *link, struct device *supplier)
+{
+ refcount_add(2, &link->rpm_active);
+ pm_runtime_get_noresume(supplier);
+}
+
void pm_runtime_drop_link(struct device *dev)
{
spin_lock_irq(&dev->power.lock);