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V4L/DVB (8772): cx18: Convert cx18_queue buffers member to atomic_t 

cx18: Convert cx18_queue buffers member to atomic_t.  This allows safe
concurrent access to check if a queue has data without having to acquire the
queue spinlock.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Andy Walls 2008-08-22 21:03:11 -03:00 committed by Mauro Carvalho Chehab
parent 59ba2b0022
commit b04bce476c
4 changed files with 11 additions and 10 deletions
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2
drivers/media/video/cx18/cx18-driver.h
View File

@ -216,7 +216,7 @@ struct cx18_buffer {
struct cx18_queue {
struct list_head list;
u32 buffers;
atomic_t buffers;
u32 bytesused;
};

4
drivers/media/video/cx18/cx18-fileops.c
View File

@ -223,7 +223,7 @@ static struct cx18_buffer *cx18_get_buffer(struct cx18_stream *s, int non_block,
prepare_to_wait(&s->waitq, &wait, TASK_INTERRUPTIBLE);
/* New buffers might have become available before we were added
to the waitqueue */
if (!s->q_full.buffers)
if (!atomic_read(&s->q_full.buffers))
schedule();
finish_wait(&s->waitq, &wait);
if (signal_pending(current)) {
@ -509,7 +509,7 @@ unsigned int cx18_v4l2_enc_poll(struct file *filp, poll_table *wait)
CX18_DEBUG_HI_FILE("Encoder poll\n");
poll_wait(filp, &s->waitq, wait);
if (s->q_full.buffers || s->q_io.buffers)
if (atomic_read(&s->q_full.buffers) || atomic_read(&s->q_io.buffers))
return POLLIN | POLLRDNORM;
if (eof)
return POLLHUP;

3
drivers/media/video/cx18/cx18-ioctl.c
View File

@ -731,7 +731,8 @@ static int cx18_log_status(struct file *file, void *fh)
continue;
CX18_INFO("Stream %s: status 0x%04lx, %d%% of %d KiB (%d buffers) in use\n",
s->name, s->s_flags,
(s->buffers - s->q_free.buffers) * 100 / s->buffers,
(s->buffers - atomic_read(&s->q_free.buffers))
* 100 / s->buffers,
(s->buffers * s->buf_size) / 1024, s->buffers);
}
CX18_INFO("Read MPEG/VBI: %lld/%lld bytes\n",

12
drivers/media/video/cx18/cx18-queue.c
View File

@ -37,7 +37,7 @@ void cx18_buf_swap(struct cx18_buffer *buf)
void cx18_queue_init(struct cx18_queue *q)
{
INIT_LIST_HEAD(&q->list);
q->buffers = 0;
atomic_set(&q->buffers, 0);
q->bytesused = 0;
}
@ -54,7 +54,7 @@ void cx18_enqueue(struct cx18_stream *s, struct cx18_buffer *buf,
}
spin_lock_irqsave(&s->qlock, flags);
list_add_tail(&buf->list, &q->list);
q->buffers++;
atomic_inc(&q->buffers);
q->bytesused += buf->bytesused - buf->readpos;
spin_unlock_irqrestore(&s->qlock, flags);
}
@ -68,7 +68,7 @@ struct cx18_buffer *cx18_dequeue(struct cx18_stream *s, struct cx18_queue *q)
if (!list_empty(&q->list)) {
buf = list_entry(q->list.next, struct cx18_buffer, list);
list_del_init(q->list.next);
q->buffers--;
atomic_dec(&q->buffers);
q->bytesused -= buf->bytesused - buf->readpos;
}
spin_unlock_irqrestore(&s->qlock, flags);
@ -92,8 +92,8 @@ struct cx18_buffer *cx18_queue_get_buf_irq(struct cx18_stream *s, u32 id,
/* the transport buffers are handled differently,
they are not moved to the full queue */
if (s->type != CX18_ENC_STREAM_TYPE_TS) {
s->q_free.buffers--;
s->q_full.buffers++;
atomic_dec(&s->q_free.buffers);
atomic_inc(&s->q_full.buffers);
s->q_full.bytesused += buf->bytesused;
list_move_tail(&buf->list, &s->q_full.list);
}
@ -119,7 +119,7 @@ static void cx18_queue_flush(struct cx18_stream *s, struct cx18_queue *q)
buf = list_entry(q->list.next, struct cx18_buffer, list);
list_move_tail(q->list.next, &s->q_free.list);
buf->bytesused = buf->readpos = buf->b_flags = 0;
s->q_free.buffers++;
atomic_inc(&s->q_free.buffers);
}
cx18_queue_init(q);
spin_unlock_irqrestore(&s->qlock, flags);