From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit e2f3cd831a280fc226118d9369bf3f77aab58c56 ]
After commit ead18c23c263 ("driver core: Introduce device links reference counting"), if there is a link between the given supplier and the given consumer already, device_link_add() will refcount it and return it unconditionally without updating its flags. It is possible, however, that the second (or any subsequent) caller of device_link_add() for the same consumer-supplier pair will pass DL_FLAG_PM_RUNTIME, possibly along with DL_FLAG_RPM_ACTIVE, in flags to it and the existing link may not behave as expected then.
First, if DL_FLAG_PM_RUNTIME is not set in the existing link's flags at all, it needs to be set like during the original initialization of the link.
Second, if DL_FLAG_RPM_ACTIVE is passed to device_link_add() in flags (in addition to DL_FLAG_PM_RUNTIME), the existing link should to be updated to reflect the "active" runtime PM configuration of the consumer-supplier pair and extra care must be taken here to avoid possible destructive races with runtime PM of the consumer.
To that end, redefine the rpm_active field in struct device_link as a refcount, initialize it to 1 and make rpm_resume() (for the consumer) and device_link_add() increment it whenever they acquire a runtime PM reference on the supplier device. Accordingly, make rpm_suspend() (for the consumer) and pm_runtime_clean_up_links() decrement it and drop runtime PM references to the supplier device in a loop until rpm_active becones 1 again.
Fixes: ead18c23c263 ("driver core: Introduce device links reference counting") Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 45 ++++++++++++++++++++++++------------ drivers/base/power/runtime.c | 26 +++++++++------------ include/linux/device.h | 2 +- 3 files changed, 42 insertions(+), 31 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index c228b4ebf554..20ae18f44dcd 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -165,6 +165,19 @@ void device_pm_move_to_tail(struct device *dev) device_links_read_unlock(idx); }
+static void device_link_rpm_prepare(struct device *consumer, + struct device *supplier) +{ + pm_runtime_new_link(consumer); + /* + * If the link is being added by the consumer driver at probe time, + * balance the decrementation of the supplier's runtime PM usage counter + * after consumer probe in driver_probe_device(). + */ + if (consumer->links.status == DL_DEV_PROBING) + pm_runtime_get_noresume(supplier); +} + /** * device_link_add - Create a link between two devices. * @consumer: Consumer end of the link. @@ -201,7 +214,6 @@ struct device_link *device_link_add(struct device *consumer, struct device *supplier, u32 flags) { struct device_link *link; - bool rpm_put_supplier = false;
if (!consumer || !supplier || (flags & DL_FLAG_STATELESS && @@ -213,7 +225,6 @@ struct device_link *device_link_add(struct device *consumer, pm_runtime_put_noidle(supplier); return NULL; } - rpm_put_supplier = true; }
device_links_write_lock(); @@ -249,6 +260,15 @@ struct device_link *device_link_add(struct device *consumer, if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER) link->flags |= DL_FLAG_AUTOREMOVE_SUPPLIER;
+ if (flags & DL_FLAG_PM_RUNTIME) { + if (!(link->flags & DL_FLAG_PM_RUNTIME)) { + device_link_rpm_prepare(consumer, supplier); + link->flags |= DL_FLAG_PM_RUNTIME; + } + if (flags & DL_FLAG_RPM_ACTIVE) + refcount_inc(&link->rpm_active); + } + kref_get(&link->kref); goto out; } @@ -257,20 +277,15 @@ struct device_link *device_link_add(struct device *consumer, if (!link) goto out;
+ refcount_set(&link->rpm_active, 1); + if (flags & DL_FLAG_PM_RUNTIME) { - if (flags & DL_FLAG_RPM_ACTIVE) { - link->rpm_active = true; - rpm_put_supplier = false; - } - pm_runtime_new_link(consumer); - /* - * If the link is being added by the consumer driver at probe - * time, balance the decrementation of the supplier's runtime PM - * usage counter after consumer probe in driver_probe_device(). - */ - if (consumer->links.status == DL_DEV_PROBING) - pm_runtime_get_noresume(supplier); + if (flags & DL_FLAG_RPM_ACTIVE) + refcount_inc(&link->rpm_active); + + device_link_rpm_prepare(consumer, supplier); } + get_device(supplier); link->supplier = supplier; INIT_LIST_HEAD(&link->s_node); @@ -333,7 +348,7 @@ struct device_link *device_link_add(struct device *consumer, device_pm_unlock(); device_links_write_unlock();
- if (rpm_put_supplier) + if ((flags & DL_FLAG_PM_RUNTIME && flags & DL_FLAG_RPM_ACTIVE) && !link) pm_runtime_put(supplier);
return link; diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index beb85c31f3fa..b914932d3ca1 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -268,11 +268,8 @@ static int rpm_get_suppliers(struct device *dev) list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) { int retval;
- if (!(link->flags & DL_FLAG_PM_RUNTIME)) - continue; - - if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND || - link->rpm_active) + if (!(link->flags & DL_FLAG_PM_RUNTIME) || + READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) continue;
retval = pm_runtime_get_sync(link->supplier); @@ -281,7 +278,7 @@ static int rpm_get_suppliers(struct device *dev) pm_runtime_put_noidle(link->supplier); return retval; } - link->rpm_active = true; + refcount_inc(&link->rpm_active); } return 0; } @@ -290,12 +287,13 @@ static void rpm_put_suppliers(struct device *dev) { struct device_link *link;
- list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) - if (link->rpm_active && - READ_ONCE(link->status) != DL_STATE_SUPPLIER_UNBIND) { + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) { + if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) + continue; + + while (refcount_dec_not_one(&link->rpm_active)) pm_runtime_put(link->supplier); - link->rpm_active = false; - } + } }
/** @@ -1531,7 +1529,7 @@ void pm_runtime_remove(struct device *dev) * * Check links from this device to any consumers and if any of them have active * runtime PM references to the device, drop the usage counter of the device - * (once per link). + * (as many times as needed). * * Links with the DL_FLAG_STATELESS flag set are ignored. * @@ -1553,10 +1551,8 @@ void pm_runtime_clean_up_links(struct device *dev) if (link->flags & DL_FLAG_STATELESS) continue;
- if (link->rpm_active) { + while (refcount_dec_not_one(&link->rpm_active)) pm_runtime_put_noidle(dev); - link->rpm_active = false; - } }
device_links_read_unlock(idx); diff --git a/include/linux/device.h b/include/linux/device.h index 19dd8852602c..b8fd2a1f859d 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -849,7 +849,7 @@ struct device_link { struct list_head c_node; enum device_link_state status; u32 flags; - bool rpm_active; + refcount_t rpm_active; struct kref kref; #ifdef CONFIG_SRCU struct rcu_head rcu_head;