[PATCH] Add a semaphore to struct device to synchronize calls to its driver.
This adds a per-device semaphore that is taken before every call from the core to a
driver method. This prevents e.g. simultaneous calls to the ->suspend() or ->resume()
and ->probe() or ->release(), potentially saving a whole lot of headaches.
It also moves us a step closer to removing the bus rwsem, since it protects the fields
in struct device that are modified by the core.
Signed-off-by: Patrick Mochel <mochel@digitalimplant.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/base/power/resume.c b/drivers/base/power/resume.c
index 2646897..bdd96b0 100644
--- a/drivers/base/power/resume.c
+++ b/drivers/base/power/resume.c
@@ -22,6 +22,9 @@
int resume_device(struct device * dev)
{
+ int error = 0;
+
+ down(&dev->sem);
if (dev->power.pm_parent
&& dev->power.pm_parent->power.power_state) {
dev_err(dev, "PM: resume from %d, parent %s still %d\n",
@@ -31,9 +34,10 @@
}
if (dev->bus && dev->bus->resume) {
dev_dbg(dev,"resuming\n");
- return dev->bus->resume(dev);
+ error = dev->bus->resume(dev);
}
- return 0;
+ up(&dev->sem);
+ return error;
}