Kevin Hilman <khil...@ti.com> writes:
[...]
> If the device bus type's or driver's ->probe() or ->remove()
> callback runs pm_runtime_suspend() or pm_runtime_idle() or their
> asynchronous counterparts, they will fail returning -EAGAIN, because
> the device's usage counter is incremented by the core before
> executing ->probe() and ->remove(). Still, it may be desirable to
> suspend the device as soon as ->probe() or ->remove() has finished,
> so the PM core uses pm_runtime_idle_sync() to invoke the
> subsystem-level idle callback for the device at that time.
[...]
> Another curiosity is that, contrary to the above documentation, there is
> no usage_count increment before the bus/driver ->remove() (although
> there is a _get_sync/_put_sync around the sysfs_remove and notifier just
> before the bus/driver->remove().
OK, so the ->probe() part has been explained and makes sense, but I
would expect ->remove() to be similarily protected (as the documentation
states.) But that is not the case. Is that a bug? If so, patch below
makes the code match the documentation.
Kevin
>From eef73ab2feb203bacb57dc35862f2a9969b61593 Mon Sep 17 00:00:00 2001
From: Kevin Hilman <khil...@ti.com>
Date: Fri, 1 Jul 2011 07:37:47 -0700
Subject: [PATCH] driver core: prevent runtime PM races with ->remove()
Runtime PM Documentation states that the runtime PM usage count is
incremented during driver ->probe() and ->remove(). This is designed
to prevent driver runtime PM races with subsystems which may initiate
runtime PM transitions before during and after drivers are loaded.
Current code increments the usage_count during ->probe() but not
during ->remove(). This patch fixes the ->remove() part and makes the
code match the documentation.
Signed-off-by: Kevin Hilman <khil...@ti.com>
---
drivers/base/dd.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 6658da7..47e079d 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -329,13 +329,13 @@ static void __device_release_driver(struct device *dev)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_UNBIND_DRIVER,
dev);
-
- pm_runtime_put_sync(dev);
-
if (dev->bus && dev->bus->remove)
dev->bus->remove(dev);
else if (drv->remove)
drv->remove(dev);
+
+ pm_runtime_put_sync(dev);
+
devres_release_all(dev);
dev->driver = NULL;
klist_remove(&dev->p->knode_driver);
--
1.7.4
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