diff options
| author | Lukas Wunner <lukas@wunner.de> | 2018-02-10 19:27:12 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2018-02-27 18:10:42 +0100 |
| commit | ead18c23c263374ed098a7d955b29b4a466d4573 (patch) | |
| tree | 17e0951e486bd5ba4b757028c0ffef88c4d34715 /include/linux/device.h | |
| parent | da997b22c40473b7db60bde6ea188d35565d10c8 (diff) | |
driver core: Introduce device links reference counting
If device_link_add() is invoked multiple times with the same supplier
and consumer combo, it will create the link on first addition and
return a pointer to the already existing link on all subsequent
additions.
The semantics for device_link_del() are quite different, it deletes
the link unconditionally, so multiple invocations are not allowed.
In other words, this snippet ...
struct device *dev1, *dev2;
struct device_link *link1, *link2;
link1 = device_link_add(dev1, dev2, 0);
link2 = device_link_add(dev1, dev2, 0);
device_link_del(link1);
device_link_del(link2);
... causes the following crash:
WARNING: CPU: 4 PID: 2686 at drivers/base/power/runtime.c:1611 pm_runtime_drop_link+0x40/0x50
[...]
list_del corruption, 0000000039b800a4->prev is LIST_POISON2 (00000000ecf79852)
kernel BUG at lib/list_debug.c:50!
The issue isn't as arbitrary as it may seem: Imagine a device link
which is added in both the supplier's and the consumer's ->probe hook.
The two drivers can't just call device_link_del() in their ->remove hook
without coordination.
Fix by counting multiple additions and dropping the device link only
when the last addition is unwound.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
[ rjw: Subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/device.h')
| -rw-r--r-- | include/linux/device.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/device.h b/include/linux/device.h index b093405ed525..abf952c82c6d 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -769,6 +769,7 @@ enum device_link_state { * @status: The state of the link (with respect to the presence of drivers). * @flags: Link flags. * @rpm_active: Whether or not the consumer device is runtime-PM-active. + * @kref: Count repeated addition of the same link. * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks. */ struct device_link { @@ -779,6 +780,7 @@ struct device_link { enum device_link_state status; u32 flags; bool rpm_active; + struct kref kref; #ifdef CONFIG_SRCU struct rcu_head rcu_head; #endif |