diff options
Diffstat (limited to 'drivers/staging/comedi/comedi_buf.c')
| -rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index fd2a92e29fb..06dd544ec2c 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -273,14 +273,17 @@ unsigned int comedi_buf_read_n_available(struct comedi_async *async) { unsigned num_bytes; - if (async == NULL) + if (!async) return 0; + num_bytes = async->munge_count - async->buf_read_count; - /* barrier insures the read of munge_count in this - query occurs before any following reads of the buffer which - might be based on the return value from this query. + + /* + * ensure the async buffer 'counts' are read before we + * attempt to read data from the buffer */ smp_rmb(); + return num_bytes; } EXPORT_SYMBOL(comedi_buf_read_n_available); |