At 12 Nov 2013 16:14:17 +0000, Oskar Schirmer wrote: > > Calculated for data transfer, the local variable appl_ptr is reused, > changed and written back later, though the lock was not held during > the transfer earlier. Admitted, destiny of the lock is not obvious > at all, but this looks much like a race condition candidate, so make > sure to have some original appl_ptr value to work on.
No, appl_ptr doesn't have to be re-read at that point. Otherwise the value will become inconsistent. This is the write operation to a stream and it's exclusive. The lock is needed to protect the PCM state change (e.g. stopped from an irq handler). thanks, Takashi > > Two occurences. > > Signed-off-by: Oskar Schirmer <os...@scara.com> > --- > sound/core/pcm_lib.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c > index 6e03b46..47e836a 100644 > --- a/sound/core/pcm_lib.c > +++ b/sound/core/pcm_lib.c > @@ -2051,6 +2051,7 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct > snd_pcm_substream *substream, > default: > break; > } > + appl_ptr = runtime->control->appl_ptr; > appl_ptr += frames; > if (appl_ptr >= runtime->boundary) > appl_ptr -= runtime->boundary; > @@ -2283,6 +2284,7 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct > snd_pcm_substream *substream, > default: > break; > } > + appl_ptr = runtime->control->appl_ptr; > appl_ptr += frames; > if (appl_ptr >= runtime->boundary) > appl_ptr -= runtime->boundary; > -- > 1.7.9.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
