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V4L/DVB (6601): V4L: videobuf-core locking fixes and comments
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- Add comments to functions that require that caller hold q->lock
- Add __videobuf_mmap_free that doesn't hold q->lock for use within videobuf
- Add locking to videobuf_mmap_free
- Fix linux/drivers/media/common/saa7146_video.c which was holding lock around
  videobuf_read_stop
- Add locking to functions that operate on a queue
- Add videobuf_stop to take care of stopping in both the read and stream case

TODO: bttv still has an unsafe call to videobuf_queue_is_busy

Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
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Brandon Philips authored and Mauro Carvalho Chehab committed Dec 11, 2007
1 parent 63337dd commit 19bc513
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Showing 3 changed files with 161 additions and 93 deletions.
5 changes: 1 addition & 4 deletions drivers/media/common/saa7146_video.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1440,10 +1440,7 @@ static void video_close(struct saa7146_dev *dev, struct file *file)
err = saa7146_stop_preview(fh);
}

// release all capture buffers
mutex_lock(&q->lock);
videobuf_read_stop(q);
mutex_unlock(&q->lock);
videobuf_stop(q);

/* hmm, why is this function declared void? */
/* return err */
Expand Down
247 changes: 158 additions & 89 deletions drivers/media/video/videobuf-core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,7 @@ void videobuf_queue_core_init(struct videobuf_queue* q,
INIT_LIST_HEAD(&q->stream);
}

/* Locking: Only usage in bttv unsafe find way to remove */
int videobuf_queue_is_busy(struct videobuf_queue *q)
{
int i;
Expand Down Expand Up @@ -178,6 +179,7 @@ int videobuf_queue_is_busy(struct videobuf_queue *q)
return 0;
}

/* Locking: Caller holds q->lock */
void videobuf_queue_cancel(struct videobuf_queue *q)
{
unsigned long flags=0;
Expand Down Expand Up @@ -208,6 +210,7 @@ void videobuf_queue_cancel(struct videobuf_queue *q)

/* --------------------------------------------------------------------- */

/* Locking: Caller holds q->lock */
enum v4l2_field videobuf_next_field(struct videobuf_queue *q)
{
enum v4l2_field field = q->field;
Expand All @@ -226,6 +229,7 @@ enum v4l2_field videobuf_next_field(struct videobuf_queue *q)
return field;
}

/* Locking: Caller holds q->lock */
static void videobuf_status(struct videobuf_queue *q, struct v4l2_buffer *b,
struct videobuf_buffer *vb, enum v4l2_buf_type type)
{
Expand Down Expand Up @@ -281,20 +285,108 @@ static void videobuf_status(struct videobuf_queue *q, struct v4l2_buffer *b,
b->sequence = vb->field_count >> 1;
}

/* Locking: Caller holds q->lock */
static int __videobuf_mmap_free(struct videobuf_queue *q)
{
int i;
int rc;

if (!q)
return 0;

MAGIC_CHECK(q->int_ops->magic,MAGIC_QTYPE_OPS);

rc = CALL(q,mmap_free,q);
if (rc<0)
return rc;

for (i = 0; i < VIDEO_MAX_FRAME; i++) {
if (NULL == q->bufs[i])
continue;
q->ops->buf_release(q,q->bufs[i]);
kfree(q->bufs[i]);
q->bufs[i] = NULL;
}

return rc;
}

int videobuf_mmap_free(struct videobuf_queue *q)
{
int ret;
mutex_lock(&q->lock);
ret = __videobuf_mmap_free(q);
mutex_unlock(&q->lock);
return ret;
}

/* Locking: Caller holds q->lock */
static int __videobuf_mmap_setup(struct videobuf_queue *q,
unsigned int bcount, unsigned int bsize,
enum v4l2_memory memory)
{
unsigned int i;
int err;

MAGIC_CHECK(q->int_ops->magic,MAGIC_QTYPE_OPS);

err = __videobuf_mmap_free(q);
if (0 != err)
return err;

/* Allocate and initialize buffers */
for (i = 0; i < bcount; i++) {
q->bufs[i] = videobuf_alloc(q);

if (q->bufs[i] == NULL)
break;

q->bufs[i]->i = i;
q->bufs[i]->input = UNSET;
q->bufs[i]->memory = memory;
q->bufs[i]->bsize = bsize;
switch (memory) {
case V4L2_MEMORY_MMAP:
q->bufs[i]->boff = bsize * i;
break;
case V4L2_MEMORY_USERPTR:
case V4L2_MEMORY_OVERLAY:
/* nothing */
break;
}
}

if (!i)
return -ENOMEM;

dprintk(1,"mmap setup: %d buffers, %d bytes each\n",
i, bsize);

return i;
}

int videobuf_mmap_setup(struct videobuf_queue *q,
unsigned int bcount, unsigned int bsize,
enum v4l2_memory memory)
{
int ret;
mutex_lock(&q->lock);
ret = __videobuf_mmap_setup(q, bcount, bsize, memory);
mutex_unlock(&q->lock);
return ret;
}

int videobuf_reqbufs(struct videobuf_queue *q,
struct v4l2_requestbuffers *req)
{
unsigned int size,count;
int retval;

if (req->type != q->type) {
dprintk(1,"reqbufs: queue type invalid\n");
return -EINVAL;
}
if (req->count < 1) {
dprintk(1,"reqbufs: count invalid (%d)\n",req->count);
return -EINVAL;
}

if (req->memory != V4L2_MEMORY_MMAP &&
req->memory != V4L2_MEMORY_USERPTR &&
req->memory != V4L2_MEMORY_OVERLAY) {
Expand All @@ -303,6 +395,12 @@ int videobuf_reqbufs(struct videobuf_queue *q,
}

mutex_lock(&q->lock);
if (req->type != q->type) {
dprintk(1,"reqbufs: queue type invalid\n");
retval = -EINVAL;
goto done;
}

if (q->streaming) {
dprintk(1,"reqbufs: streaming already exists\n");
retval = -EBUSY;
Expand All @@ -323,7 +421,7 @@ int videobuf_reqbufs(struct videobuf_queue *q,
dprintk(1,"reqbufs: bufs=%d, size=0x%x [%d pages total]\n",
count, size, (count*size)>>PAGE_SHIFT);

retval = videobuf_mmap_setup(q,count,size,req->memory);
retval = __videobuf_mmap_setup(q,count,size,req->memory);
if (retval < 0) {
dprintk(1,"reqbufs: mmap setup returned %d\n",retval);
goto done;
Expand All @@ -338,20 +436,28 @@ int videobuf_reqbufs(struct videobuf_queue *q,

int videobuf_querybuf(struct videobuf_queue *q, struct v4l2_buffer *b)
{
int ret = -EINVAL;

mutex_lock(&q->lock);
if (unlikely(b->type != q->type)) {
dprintk(1,"querybuf: Wrong type.\n");
return -EINVAL;
goto done;
}
if (unlikely(b->index < 0 || b->index >= VIDEO_MAX_FRAME)) {
dprintk(1,"querybuf: index out of range.\n");
return -EINVAL;
goto done;
}
if (unlikely(NULL == q->bufs[b->index])) {
dprintk(1,"querybuf: buffer is null.\n");
return -EINVAL;
goto done;
}

videobuf_status(q,b,q->bufs[b->index],q->type);
return 0;

ret = 0;
done:
mutex_unlock(&q->lock);
return ret;
}

int videobuf_qbuf(struct videobuf_queue *q,
Expand Down Expand Up @@ -541,22 +647,30 @@ int videobuf_streamon(struct videobuf_queue *q)
return retval;
}

int videobuf_streamoff(struct videobuf_queue *q)
/* Locking: Caller holds q->lock */
static int __videobuf_streamoff(struct videobuf_queue *q)
{
int retval = -EINVAL;

mutex_lock(&q->lock);
if (!q->streaming)
goto done;
return -EINVAL;

videobuf_queue_cancel(q);
q->streaming = 0;
retval = 0;

done:
return 0;
}

int videobuf_streamoff(struct videobuf_queue *q)
{
int retval;

mutex_lock(&q->lock);
retval = __videobuf_streamoff(q);
mutex_unlock(&q->lock);

return retval;
}

/* Locking: Caller holds q->lock */
static ssize_t videobuf_read_zerocopy(struct videobuf_queue *q,
char __user *data,
size_t count, loff_t *ppos)
Expand Down Expand Up @@ -691,6 +805,7 @@ ssize_t videobuf_read_one(struct videobuf_queue *q,
return retval;
}

/* Locking: Caller holds q->lock */
int videobuf_read_start(struct videobuf_queue *q)
{
enum v4l2_field field;
Expand All @@ -705,7 +820,7 @@ int videobuf_read_start(struct videobuf_queue *q)
count = VIDEO_MAX_FRAME;
size = PAGE_ALIGN(size);

err = videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
err = __videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
if (err < 0)
return err;

Expand All @@ -728,12 +843,13 @@ int videobuf_read_start(struct videobuf_queue *q)
return 0;
}

void videobuf_read_stop(struct videobuf_queue *q)
static void __videobuf_read_stop(struct videobuf_queue *q)
{
int i;


videobuf_queue_cancel(q);
videobuf_mmap_free(q);
__videobuf_mmap_free(q);
INIT_LIST_HEAD(&q->stream);
for (i = 0; i < VIDEO_MAX_FRAME; i++) {
if (NULL == q->bufs[i])
Expand All @@ -743,8 +859,30 @@ void videobuf_read_stop(struct videobuf_queue *q)
}
q->read_buf = NULL;
q->reading = 0;

}

void videobuf_read_stop(struct videobuf_queue *q)
{
mutex_lock(&q->lock);
__videobuf_read_stop(q);
mutex_unlock(&q->lock);
}

void videobuf_stop(struct videobuf_queue *q)
{
mutex_lock(&q->lock);

if (q->streaming)
__videobuf_streamoff(q);

if (q->reading)
__videobuf_read_stop(q);

mutex_unlock(&q->lock);
}


ssize_t videobuf_read_stream(struct videobuf_queue *q,
char __user *data, size_t count, loff_t *ppos,
int vbihack, int nonblocking)
Expand Down Expand Up @@ -858,75 +996,6 @@ unsigned int videobuf_poll_stream(struct file *file,
return rc;
}

int videobuf_mmap_setup(struct videobuf_queue *q,
unsigned int bcount, unsigned int bsize,
enum v4l2_memory memory)
{
unsigned int i;
int err;

MAGIC_CHECK(q->int_ops->magic,MAGIC_QTYPE_OPS);

err = videobuf_mmap_free(q);
if (0 != err)
return err;

/* Allocate and initialize buffers */
for (i = 0; i < bcount; i++) {
q->bufs[i] = videobuf_alloc(q);

if (q->bufs[i] == NULL)
break;

q->bufs[i]->i = i;
q->bufs[i]->input = UNSET;
q->bufs[i]->memory = memory;
q->bufs[i]->bsize = bsize;
switch (memory) {
case V4L2_MEMORY_MMAP:
q->bufs[i]->boff = bsize * i;
break;
case V4L2_MEMORY_USERPTR:
case V4L2_MEMORY_OVERLAY:
/* nothing */
break;
}
}

if (!i)
return -ENOMEM;

dprintk(1,"mmap setup: %d buffers, %d bytes each\n",
i, bsize);

return i;
}

int videobuf_mmap_free(struct videobuf_queue *q)
{
int i;
int rc;

if (!q)
return 0;

MAGIC_CHECK(q->int_ops->magic,MAGIC_QTYPE_OPS);

rc = CALL(q,mmap_free,q);
if (rc<0)
return rc;

for (i = 0; i < VIDEO_MAX_FRAME; i++) {
if (NULL == q->bufs[i])
continue;
q->ops->buf_release(q,q->bufs[i]);
kfree(q->bufs[i]);
q->bufs[i] = NULL;
}

return rc;
}

int videobuf_mmap_mapper(struct videobuf_queue *q,
struct vm_area_struct *vma)
{
Expand Down Expand Up @@ -989,8 +1058,8 @@ EXPORT_SYMBOL_GPL(videobuf_dqbuf);
EXPORT_SYMBOL_GPL(videobuf_streamon);
EXPORT_SYMBOL_GPL(videobuf_streamoff);

EXPORT_SYMBOL_GPL(videobuf_read_start);
EXPORT_SYMBOL_GPL(videobuf_read_stop);
EXPORT_SYMBOL_GPL(videobuf_stop);
EXPORT_SYMBOL_GPL(videobuf_read_stream);
EXPORT_SYMBOL_GPL(videobuf_read_one);
EXPORT_SYMBOL_GPL(videobuf_poll_stream);
Expand Down
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