[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/suspend.c b/drivers/base/power/suspend.c
index 0ec44ef..807e13f 100644
--- a/drivers/base/power/suspend.c
+++ b/drivers/base/power/suspend.c
@@ -39,6 +39,7 @@
{
int error = 0;
+ down(&dev->sem);
if (dev->power.power_state) {
dev_dbg(dev, "PM: suspend %d-->%d\n",
dev->power.power_state, state);
@@ -58,7 +59,7 @@
dev_dbg(dev, "suspending\n");
error = dev->bus->suspend(dev, state);
}
-
+ up(&dev->sem);
return error;
}