Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=96b19062e741b715cf399312c30e0672d8889569
Commit: 96b19062e741b715cf399312c30e0672d8889569
Parent: 1b9c12ba2fdf802a23630f70eddb0e821296634e
Author: Stefan Richter <[EMAIL PROTECTED]>
AuthorDate: Sat Feb 2 15:01:09 2008 +0100
Committer: Stefan Richter <[EMAIL PROTECTED]>
CommitDate: Sat Feb 16 15:40:33 2008 +0100
firewire: fix "kobject_add failed for fw* with -EEXIST"
There is a race between shutdown and creation of devices: fw-core may
attempt to add a device with the same name of an already existing
device. http://bugzilla.kernel.org/show_bug.cgi?id=9828
Impact of the bug: Happens rarely (when shutdown of a device coincides
with creation of another), forces the user to unplug and replug the new
device to get it working.
The fix is obvious: Free the minor number *after* instead of *before*
device_unregister(). This requires to take an additional reference of
the fw_device as long as the IDR tree points to it.
And while we are at it, we fix an additional race condition:
fw_device_op_open() took its reference of the fw_device a little bit too
late, hence was in danger to access an already invalid fw_device.
Signed-off-by: Stefan Richter <[EMAIL PROTECTED]>
---
drivers/firewire/fw-cdev.c | 8 +++++---
drivers/firewire/fw-device.c | 20 ++++++++++++++------
drivers/firewire/fw-device.h | 2 +-
3 files changed, 20 insertions(+), 10 deletions(-)
diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index 7e73cba..44ccee2 100644
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -109,15 +109,17 @@ static int fw_device_op_open(struct inode *inode, struct
file *file)
struct client *client;
unsigned long flags;
- device = fw_device_from_devt(inode->i_rdev);
+ device = fw_device_get_by_devt(inode->i_rdev);
if (device == NULL)
return -ENODEV;
client = kzalloc(sizeof(*client), GFP_KERNEL);
- if (client == NULL)
+ if (client == NULL) {
+ fw_device_put(device);
return -ENOMEM;
+ }
- client->device = fw_device_get(device);
+ client->device = device;
INIT_LIST_HEAD(&client->event_list);
INIT_LIST_HEAD(&client->resource_list);
spin_lock_init(&client->lock);
diff --git a/drivers/firewire/fw-device.c b/drivers/firewire/fw-device.c
index de9066e..c04c288 100644
--- a/drivers/firewire/fw-device.c
+++ b/drivers/firewire/fw-device.c
@@ -610,12 +610,14 @@ static DECLARE_RWSEM(idr_rwsem);
static DEFINE_IDR(fw_device_idr);
int fw_cdev_major;
-struct fw_device *fw_device_from_devt(dev_t devt)
+struct fw_device *fw_device_get_by_devt(dev_t devt)
{
struct fw_device *device;
down_read(&idr_rwsem);
device = idr_find(&fw_device_idr, MINOR(devt));
+ if (device)
+ fw_device_get(device);
up_read(&idr_rwsem);
return device;
@@ -627,13 +629,14 @@ static void fw_device_shutdown(struct work_struct *work)
container_of(work, struct fw_device, work.work);
int minor = MINOR(device->device.devt);
- down_write(&idr_rwsem);
- idr_remove(&fw_device_idr, minor);
- up_write(&idr_rwsem);
-
fw_device_cdev_remove(device);
device_for_each_child(&device->device, NULL, shutdown_unit);
device_unregister(&device->device);
+
+ down_write(&idr_rwsem);
+ idr_remove(&fw_device_idr, minor);
+ up_write(&idr_rwsem);
+ fw_device_put(device);
}
static struct device_type fw_device_type = {
@@ -682,10 +685,13 @@ static void fw_device_init(struct work_struct *work)
}
err = -ENOMEM;
+
+ fw_device_get(device);
down_write(&idr_rwsem);
if (idr_pre_get(&fw_device_idr, GFP_KERNEL))
err = idr_get_new(&fw_device_idr, device, &minor);
up_write(&idr_rwsem);
+
if (err < 0)
goto error;
@@ -741,7 +747,9 @@ static void fw_device_init(struct work_struct *work)
idr_remove(&fw_device_idr, minor);
up_write(&idr_rwsem);
error:
- put_device(&device->device);
+ fw_device_put(device); /* fw_device_idr's reference */
+
+ put_device(&device->device); /* our reference */
}
static int update_unit(struct device *dev, void *data)
diff --git a/drivers/firewire/fw-device.h b/drivers/firewire/fw-device.h
index 0854fe2..43808c0 100644
--- a/drivers/firewire/fw-device.h
+++ b/drivers/firewire/fw-device.h
@@ -77,13 +77,13 @@ fw_device_is_shutdown(struct fw_device *device)
}
struct fw_device *fw_device_get(struct fw_device *device);
+struct fw_device *fw_device_get_by_devt(dev_t devt);
void fw_device_put(struct fw_device *device);
int fw_device_enable_phys_dma(struct fw_device *device);
void fw_device_cdev_update(struct fw_device *device);
void fw_device_cdev_remove(struct fw_device *device);
-struct fw_device *fw_device_from_devt(dev_t devt);
extern int fw_cdev_major;
struct fw_unit {
-
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