Commit a695f167 authored by Frank Munzert's avatar Frank Munzert Committed by Heiko Carstens
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[S390] vmur: Use wait queue instead of mutex to serialize open 



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: default avatarFrank Munzert <munzert@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent 92bf435f

drivers/s390/char/vmur.c

+17 −7
Original line number Diff line number Diff line
@@ -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;



	spin_lock(&urd->open_lock);

	while (urd->open_flag) {

		spin_unlock(&urd->open_lock);

		if (file->f_flags & O_NONBLOCK) {

		if (!mutex_trylock(&urd->open_mutex)) {

			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;

drivers/s390/char/vmur.h

+3 −1
Original line number Diff line number Diff line
@@ -62,7 +62,6 @@ struct file_control_block { 
struct urdev {

	struct ccw_device *cdev;	/* Backpointer to ccw device */

	struct mutex io_mutex;		/* Serialises device IO */

	struct mutex open_mutex;	/* Serialises access to device */

	struct completion *io_done;	/* do_ur_io waits; irq completes */

	struct device *device;

	struct cdev *char_device;
@@ -71,6 +70,9 @@ struct urdev { 
	int class;			/* VM device class */

	int io_request_rc;		/* return code from I/O request */

	atomic_t ref_count;		/* reference counter */

	wait_queue_head_t wait;		/* wait queue to serialize open */

	int open_flag;			/* "urdev is open" flag */

	spinlock_t open_lock;		/* serialize critical sections */

};



/*

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