Reword the comment about the need for the smp_mb().
Clarify the check to make sure the number of bytes to free is not
more than the number of bytes allocated.
Signed-off-by: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Abbott <abbobbi@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/comedi_buf.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index 971f739..70d2901 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -312,14 +312,19 @@ EXPORT_SYMBOL(comedi_buf_read_alloc);
/* transfers control of a chunk from reader to free buffer space */
unsigned comedi_buf_read_free(struct comedi_async *async, unsigned int nbytes)
{
- /* barrier insures data has been read out of
- * buffer before read count is incremented */
+ unsigned int allocated;
+
+ /*
+ * ensure data has been read out of buffer before
+ * the async read count is incremented
+ */
smp_mb();
- if ((int)(async->buf_read_count + nbytes -
- async->buf_read_alloc_count) > 0) {
+
+ allocated = comedi_buf_read_n_allocated(async);
+ if (nbytes > allocated) {
dev_info(async->subdevice->device->class_dev,
"attempted to read-free more bytes than have been read-allocated.\n");
- nbytes = async->buf_read_alloc_count - async->buf_read_count;
+ nbytes = allocated;
}
async->buf_read_count += nbytes;
async->buf_read_ptr += nbytes;
--
1.8.0
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
