Clarify the check to make sure the number of bytes to allocate is
available.
Also, cleanup the multi-line comment about the barrier.
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 | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index a12b70b..a95bb3d 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -293,14 +293,19 @@ EXPORT_SYMBOL(comedi_buf_read_n_available);
/* allocates a chunk for the reader from filled (and munged) buffer space */
unsigned comedi_buf_read_alloc(struct comedi_async *async, unsigned nbytes)
{
- if ((int)(async->buf_read_alloc_count + nbytes - async->munge_count) >
- 0) {
- nbytes = async->munge_count - async->buf_read_alloc_count;
- }
+ unsigned int available = async->munge_count - async->buf_read_alloc_count;
+
+ if (nbytes > available)
+ nbytes = available;
+
async->buf_read_alloc_count += nbytes;
- /* barrier insures read of munge_count occurs before we actually read
- data out of buffer */
+
+ /*
+ * barrier insures the read of munge_count above occurs
+ * before any following reads out of the buffer
+ */
smp_rmb();
+
return nbytes;
}
EXPORT_SYMBOL(comedi_buf_read_alloc);
--
1.8.0
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