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[S390] vmur: Use wait queue instead of mutex to serialize open

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If user space opens a unit record device node then vmur is leaving the kernel
with lock open_mutex still held to prevent other processes from opening the
device simultaneously. This causes lockdep to complain about a lock held when
returning to user space.
Now the mutex is replaced by a wait queue to serialize device open.

Signed-off-by: Frank Munzert <munzert@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Frank Munzert
2008-04-17 07:46:06 +02:00
committed by Heiko Carstens
parent 92bf435f38
commit a695f16729
2 changed files with 20 additions and 8 deletions
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24
drivers/s390/char/vmur.c
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@@ -100,7 +100,8 @@ static struct urdev *urdev_alloc(struct ccw_device *cdev)
urd->reclen = cdev->id.driver_info;
ccw_device_get_id(cdev, &urd->dev_id);
mutex_init(&urd->io_mutex);
mutex_init(&urd->open_mutex);
init_waitqueue_head(&urd->wait);
spin_lock_init(&urd->open_lock);
atomic_set(&urd->ref_count, 1);
urd->cdev = cdev;
get_device(&cdev->dev);
@@ -678,17 +679,21 @@ static int ur_open(struct inode *inode, struct file *file)
if (!urd)
return -ENXIO;
if (file->f_flags & O_NONBLOCK) {
if (!mutex_trylock(&urd->open_mutex)) {
spin_lock(&urd->open_lock);
while (urd->open_flag) {
spin_unlock(&urd->open_lock);
if (file->f_flags & O_NONBLOCK) {
rc = -EBUSY;
goto fail_put;
}
} else {
if (mutex_lock_interruptible(&urd->open_mutex)) {
if (wait_event_interruptible(urd->wait, urd->open_flag == 0)) {
rc = -ERESTARTSYS;
goto fail_put;
}
spin_lock(&urd->open_lock);
}
urd->open_flag++;
spin_unlock(&urd->open_lock);
TRACE("ur_open\n");
@@ -720,7 +725,9 @@ static int ur_open(struct inode *inode, struct file *file)
fail_urfile_free:
urfile_free(urf);
fail_unlock:
mutex_unlock(&urd->open_mutex);
spin_lock(&urd->open_lock);
urd->open_flag--;
spin_unlock(&urd->open_lock);
fail_put:
urdev_put(urd);
return rc;
@@ -731,7 +738,10 @@ static int ur_release(struct inode *inode, struct file *file)
struct urfile *urf = file->private_data;
TRACE("ur_release\n");
mutex_unlock(&urf->urd->open_mutex);
spin_lock(&urf->urd->open_lock);
urf->urd->open_flag--;
spin_unlock(&urf->urd->open_lock);
wake_up_interruptible(&urf->urd->wait);
urdev_put(urf->urd);
urfile_free(urf);
return 0;