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author | Takashi Iwai <tiwai@suse.de> | 2019-07-19 10:55:05 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-07-31 07:25:00 +0200 |
commit | 65a96bb655ecd6a5a39aeebd2ad6fd3e983c3b4c (patch) | |
tree | 44a91514e19b4024b7accf28b9d5a8889c3ae685 /sound/core | |
parent | b8e0b3ea392a7da38d46ca393c7a4e36364d45d7 (diff) | |
download | linux-stable-65a96bb655ecd6a5a39aeebd2ad6fd3e983c3b4c.tar.gz linux-stable-65a96bb655ecd6a5a39aeebd2ad6fd3e983c3b4c.tar.bz2 linux-stable-65a96bb655ecd6a5a39aeebd2ad6fd3e983c3b4c.zip |
ALSA: pcm: Fix refcount_inc() on zero usage
commit 0e279dcea0ec897af1c979ebee4ec92b461793f5 upstream.
The recent rewrite of PCM link lock management introduced the refcount
in snd_pcm_group object, managed by the kernel refcount_t API. This
caused unexpected kernel warnings when the kernel is built with
CONFIG_REFCOUNT_FULL=y. As the warning line indicates, the problem is
obviously that we start with refcount=0 and do refcount_inc() for
adding each PCM link, while refcount_t API doesn't like refcount_inc()
performed on zero.
For adapting the proper refcount_t usage, this patch changes the logic
slightly:
- The initial refcount is 1, assuming the single list entry
- The refcount is incremented / decremented at each PCM link addition
and deletion
- ... which allows us concentrating only on the refcount as a release
condition
Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204221
Reported-and-tested-by: Duncan Overbruck <kernel@duncano.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound/core')
-rw-r--r-- | sound/core/pcm_native.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 860543a4c840..12dd9b318db1 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -77,7 +77,7 @@ void snd_pcm_group_init(struct snd_pcm_group *group) spin_lock_init(&group->lock); mutex_init(&group->mutex); INIT_LIST_HEAD(&group->substreams); - refcount_set(&group->refs, 0); + refcount_set(&group->refs, 1); } /* define group lock helpers */ @@ -1096,8 +1096,7 @@ static void snd_pcm_group_unref(struct snd_pcm_group *group, if (!group) return; - do_free = refcount_dec_and_test(&group->refs) && - list_empty(&group->substreams); + do_free = refcount_dec_and_test(&group->refs); snd_pcm_group_unlock(group, substream->pcm->nonatomic); if (do_free) kfree(group); @@ -2020,6 +2019,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) snd_pcm_group_lock_irq(target_group, nonatomic); snd_pcm_stream_lock(substream1); snd_pcm_group_assign(substream1, target_group); + refcount_inc(&target_group->refs); snd_pcm_stream_unlock(substream1); snd_pcm_group_unlock_irq(target_group, nonatomic); _end: @@ -2056,13 +2056,14 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream) snd_pcm_group_lock_irq(group, nonatomic); relink_to_local(substream); + refcount_dec(&group->refs); /* detach the last stream, too */ if (list_is_singular(&group->substreams)) { relink_to_local(list_first_entry(&group->substreams, struct snd_pcm_substream, link_list)); - do_free = !refcount_read(&group->refs); + do_free = refcount_dec_and_test(&group->refs); } snd_pcm_group_unlock_irq(group, nonatomic); |