Greg KH
2005-06-21T02:51:49Z

[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>

---
commit af70316af182f4716cc5eec7e0d27fc731d164bd
tree 22fa4732c8270db8fd3f681355cd83e4b8088847
parent eb51b65005737b777e0709683b061d5f82aefd97
author mochel@digitalimplant.org <mochel@digitalimplant.org> Mon, 21 Mar 2005 10:41:04 -0800
committer Greg Kroah-Hartman <gregkh@suse.de> Mon, 20 Jun 2005 15:15:12 -0700

drivers/base/bus.c | 14 +++++++++++---
drivers/base/core.c | 1 +
drivers/base/power/resume.c | 8 ++++++--
drivers/base/power/suspend.c | 3 ++-
include/linux/device.h | 4 ++++
5 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -283,18 +283,22 @@ void device_bind_driver(struct device *
*/
int driver_probe_device(struct device_driver * drv, struct device * dev)
{
+ int error = 0;
+
if (drv->bus->match && !drv->bus->match(dev, drv))
return -ENODEV;

+ down(&dev->sem);
dev->driver = drv;
if (drv->probe) {
- int error = drv->probe(dev);
+ error = drv->probe(dev);
if (error) {
dev->driver = NULL;
+ up(&dev->sem);
return error;
}
}
-
+ up(&dev->sem);
device_bind_driver(dev);
return 0;
}
@@ -385,7 +389,10 @@ void driver_attach(struct device_driver

void device_release_driver(struct device * dev)
{
- struct device_driver * drv = dev->driver;
+ struct device_driver * drv;
+
+ down(&dev->sem);
+ drv = dev->driver;
if (drv) {
sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
sysfs_remove_link(&dev->kobj, "driver");
@@ -394,6 +401,7 @@ void device_release_driver(struct device
drv->remove(dev);
dev->driver = NULL;
}
+ up(&dev->sem);
}

diff --git a/drivers/base/core.c b/drivers/base/core.c
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -212,6 +212,7 @@ void device_initialize(struct device *de
INIT_LIST_HEAD(&dev->driver_list);
INIT_LIST_HEAD(&dev->bus_list);
INIT_LIST_HEAD(&dev->dma_pools);
+ init_MUTEX(&dev->sem);
}

/**
diff --git a/drivers/base/power/resume.c b/drivers/base/power/resume.c
--- a/drivers/base/power/resume.c
+++ b/drivers/base/power/resume.c
@@ -22,6 +22,9 @@ extern int sysdev_resume(void);

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 @@ int resume_device(struct device * dev)
}
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;
}

diff --git a/drivers/base/power/suspend.c b/drivers/base/power/suspend.c
--- a/drivers/base/power/suspend.c
+++ b/drivers/base/power/suspend.c
@@ -39,6 +39,7 @@ int suspend_device(struct device * dev,
{
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 @@ int suspend_device(struct device * dev,
dev_dbg(dev, "suspending\n");
error = dev->bus->suspend(dev, state);
}
-
+ up(&dev->sem);
return error;
}

diff --git a/include/linux/device.h b/include/linux/device.h
--- 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 */