[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>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/device.h b/include/linux/device.h
index 68a95358013d..195b327f3e19 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -264,6 +264,10 @@ struct device {
         struct kobject kobj;
         char    bus_id[BUS_ID_SIZE];    /* position on parent bus */
 
+        struct semaphore        sem;    /* semaphore to synchronize calls to
+                                         * its driver.
+                                         */
+
         struct bus_type * bus;          /* type of bus device is on */
         struct device_driver *driver;   /* which driver has allocated this
                                            device */