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driver core: Fix handling of runtime PM flags in device_link_add()

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After commit ead18c23c2 ("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: ead18c23c2 ("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>
This commit is contained in:
Rafael J. Wysocki
2019-02-01 01:49:14 +01:00
committed by Greg Kroah-Hartman
parent 5db25c9eb8
commit e2f3cd831a
3 changed files with 42 additions and 31 deletions
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26
drivers/base/power/runtime.c
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@@ -259,11 +259,8 @@ 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);
@@ -272,7 +269,7 @@ 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;
}
@@ -281,12 +278,13 @@ 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;
}
}
}
/**
@@ -1539,7 +1537,7 @@ 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.
*
@@ -1561,10 +1559,8 @@ 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);