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    Subject[PATCH 4.14 066/107] ALSA: pcm: Dont suspend stream in unrecoverable PCM state
    4.14-stable review patch.  If anyone has any objections, please let me know.


    From: Takashi Iwai <>

    commit 113ce08109f8e3b091399e7cc32486df1cff48e7 upstream.

    Currently PCM core sets each opened stream forcibly to SUSPENDED state
    via snd_pcm_suspend_all() call, and the user-space is responsible for
    re-triggering the resume manually either via snd_pcm_resume() or
    prepare call. The scheme works fine usually, but there are corner
    cases where the stream can't be resumed by that call: the streams
    still in OPEN state before finishing hw_params. When they are
    suspended, user-space cannot perform resume or prepare because they
    haven't been set up yet. The only possible recovery is to re-open the
    device, which isn't nice at all. Similarly, when a stream is in
    DISCONNECTED state, it makes no sense to change it to SUSPENDED
    state. Ditto for in SETUP state; which you can re-prepare directly.

    So, this patch addresses these issues by filtering the PCM streams to
    be suspended by checking the PCM state. When a stream is in either
    OPEN, SETUP or DISCONNECTED as well as already SUSPENDED, the suspend
    action is skipped.

    To be noted, this problem was originally reported for the PCM runtime
    PM on HD-audio. And, the runtime PM problem itself was already
    addressed (although not intended) by the code refactoring commits
    3d21ef0b49f8 ("ALSA: pcm: Suspend streams globally via device type PM
    ops") and 17bc4815de58 ("ALSA: pci: Remove superfluous
    snd_pcm_suspend*() calls"). These commits eliminated the
    snd_pcm_suspend*() calls from the runtime PM suspend callback code
    path, hence the racy OPEN state won't appear while runtime PM.
    (FWIW, the race window is between snd_pcm_open_substream() and the
    first power up in azx_pcm_open().)

    Although the runtime PM issue was already "fixed", the same problem is
    still present for the system PM, hence this patch is still needed.
    And for stable trees, this patch alone should suffice for fixing the
    runtime PM problem, too.

    Reported-and-tested-by: Jon Hunter <>
    Cc: <>
    Signed-off-by: Takashi Iwai <>
    Signed-off-by: Greg Kroah-Hartman <>

    sound/core/pcm_native.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    --- a/sound/core/pcm_native.c
    +++ b/sound/core/pcm_native.c
    @@ -1395,8 +1395,15 @@ static int snd_pcm_pause(struct snd_pcm_
    static int snd_pcm_pre_suspend(struct snd_pcm_substream *substream, int state)
    struct snd_pcm_runtime *runtime = substream->runtime;
    - if (runtime->status->state == SNDRV_PCM_STATE_SUSPENDED)
    + switch (runtime->status->state) {
    return -EBUSY;
    + /* unresumable PCM state; return -EBUSY for skipping suspend */
    + return -EBUSY;
    + }
    runtime->trigger_master = substream;
    return 0;

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