diff options
Diffstat (limited to 'drivers/staging/comedi/comedi_buf.c')
| -rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 06dd544ec2c5..971f7394a1f0 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -291,14 +291,20 @@ 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; + + 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 */ + + /* + * ensure the async buffer 'counts' are read before we + * attempt to read data from the read-alloc'ed buffer space + */ smp_rmb(); + return nbytes; } EXPORT_SYMBOL(comedi_buf_read_alloc); |