Change the rc_register_device() code so that it isn't necessary to hold any
mutex. When device_add() is called, the norm is that the device should
actually be ready for use.
Holding the mutex is a recipe for deadlocks as (for example) calling
input_register_device() is quite likely to end up in a call to
input_dev->open() which might take the same mutex (to update the user
count, see later patches).
Signed-off-by: David Härdeman <david@xxxxxxxxxxx>
---
drivers/media/rc/rc-main.c | 95 ++++++++++++++++++--------------------------
include/media/rc-core.h | 3 -
2 files changed, 40 insertions(+), 58 deletions(-)
diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index 83ea507..620cd8d 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -214,8 +214,8 @@ static struct {
* It returns the protocol names of supported protocols.
* Enabled protocols are printed in brackets.
*
- * dev->lock is taken to guard against races between device
- * registration, store_protocols and show_protocols.
+ * dev->lock is taken to guard against races between store_protocols
+ * and show_protocols.
*/
static ssize_t show_protocols(struct device *device,
struct device_attribute *mattr, char *buf)
@@ -276,8 +276,8 @@ static ssize_t show_protocols(struct device *device,
* Returns -EINVAL if an invalid protocol combination or unknown protocol name
* is used, otherwise @len.
*
- * dev->lock is taken to guard against races between device
- * registration, store_protocols and show_protocols.
+ * dev->lock is taken to guard against races between store_protocols and
+ * show_protocols.
*/
static ssize_t store_protocols(struct device *device,
struct device_attribute *mattr,
@@ -492,17 +492,14 @@ int rc_register_device(struct rc_dev *dev)
if (rc)
return rc;
- for (i = 0; i < ARRAY_SIZE(rc_dev_table); i++) {
- if (!rc_dev_table[i]) {
- rc_dev_table[i] = dev;
+ for (i = 0; i < ARRAY_SIZE(rc_dev_table); i++)
+ if (!rc_dev_table[i])
break;
- }
- }
-
- mutex_unlock(&rc_dev_table_mutex);
- if (i >= ARRAY_SIZE(rc_dev_table))
- return -ENFILE;
+ if (i >= ARRAY_SIZE(rc_dev_table)) {
+ rc = -ENFILE;
+ goto out;
+ }
dev->minor = i;
dev->dev.devt = MKDEV(rc_major, dev->minor);
@@ -512,35 +509,9 @@ int rc_register_device(struct rc_dev *dev)
if (dev->tx_ir) {
rc = kfifo_alloc(&dev->txfifo, RC_TX_KFIFO_SIZE, GFP_KERNEL);
if (rc)
- goto out_minor;
- }
-
- /*
- * Take the lock here, as the device sysfs node will appear
- * when device_add() is called, which may trigger an ir-keytable udev
- * rule, which will in turn call show_protocols and access either
- * dev->rc_map.rc_type or dev->raw->enabled_protocols before it has
- * been initialized.
- */
- mutex_lock(&dev->lock);
-
- dev->kt = rc_keytable_create(dev, dev->map_name);
- if (!dev->kt) {
- rc = -ENOMEM;
- goto out_unlock;
+ goto out;
}
- rc = device_add(&dev->dev);
- if (rc)
- goto out_keytable;
-
- path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
- printk(KERN_INFO "%s: %s as %s\n",
- dev_name(&dev->dev),
- dev->input_name ? dev->input_name : "Unspecified device",
- path ? path : "N/A");
- kfree(path);
-
if (dev->driver_type == RC_DRIVER_IR_RAW) {
/* Load raw decoders, if they aren't already */
if (!raw_init) {
@@ -550,7 +521,7 @@ int rc_register_device(struct rc_dev *dev)
}
rc = ir_raw_event_register(dev);
if (rc < 0)
- goto out_dev;
+ goto out_kfifo;
}
if (dev->change_protocol) {
@@ -559,29 +530,41 @@ int rc_register_device(struct rc_dev *dev)
goto out_raw;
}
+ rc_dev_table[i] = dev;
dev->exist = true;
- mutex_unlock(&dev->lock);
- IR_dprintk(1, "Registered rc%u (driver: %s, remote: %s, mode %s)\n",
- dev->minor,
- dev->driver_name ? dev->driver_name : "unknown",
- dev->map_name ? dev->map_name : "unknown",
- dev->driver_type == RC_DRIVER_IR_RAW ? "raw" : "cooked");
+ /* Once device_add is called, userspace might access e.g. sysfs files */
+ rc = device_add(&dev->dev);
+ if (rc)
+ goto out_chardev;
+
+ dev->kt = rc_keytable_create(dev, dev->map_name);
+ if (!dev->kt) {
+ rc = -ENOMEM;
+ goto out_device;
+ }
+
+ mutex_unlock(&rc_dev_table_mutex);
+
+ path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
+ printk(KERN_INFO "%s: %s as %s\n",
+ dev_name(&dev->dev),
+ dev->input_name ? dev->input_name : "Unspecified device",
+ path ? path : "N/A");
+ kfree(path);
return 0;
+out_device:
+ device_del(&dev->dev);
+out_chardev:
+ rc_dev_table[dev->minor] = NULL;
out_raw:
if (dev->driver_type == RC_DRIVER_IR_RAW)
ir_raw_event_unregister(dev);
-out_dev:
- device_del(&dev->dev);
-out_keytable:
- rc_keytable_destroy(dev->kt);
-out_unlock:
- mutex_unlock(&dev->lock);
-out_minor:
- mutex_lock(&rc_dev_table_mutex);
- rc_dev_table[dev->minor] = NULL;
+out_kfifo:
+ kfifo_free(&dev->txfifo);
+out:
mutex_unlock(&rc_dev_table_mutex);
return rc;
}
diff --git a/include/media/rc-core.h b/include/media/rc-core.h
index 20bd1ce..e34815b 100644
--- a/include/media/rc-core.h
+++ b/include/media/rc-core.h
@@ -203,8 +203,7 @@ struct ir_raw_event {
* @driver_name: name of the hardware driver which registered this device
* @map_name: name of the default keymap
* @rc_map: current scan/key table
- * @lock: used to ensure we've filled in all protocol details before
- * anyone can call show_protocols or store_protocols
+ * @lock: used where a more specific lock/mutex/etc is not available
* @minor: unique minor remote control device number
* @exist: used to determine if the device is still valid
* @client_list: list of clients (processes which have opened the rc chardev)
--
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