From d692c314d29a310efe875e9be05b0ccebe6b241d Mon Sep 17 00:00:00 2001 From: Christos Margiolis Date: Thu, 11 Apr 2024 20:06:50 +0200 Subject: [PATCH] sound: Implement asynchronous device detach Hot-unplugging a sound device, such as a USB sound card, whilst being consumed by an application, results in an infinite loop until either the application closes the device's file descriptor, or the channel automatically times out after hw.snd.timeout seconds. In the case of a detach however, the timeout approach is still not ideal, since we want all resources to be released immediatelly, without waiting for N seconds until we can use the bus again. The timeout mechanism works by calling chn_sleep() in chn_read() and chn_write() (see pcm/channel.c) in order to send the thread to sleep, using cv_timedwait_sig(). Since chn_sleep() sets the CHN_F_SLEEPING flag while waiting for cv_timedwait_sig() to return, we can test this flag in pcm_unregister() (called during detach) and wakeup the sleeping thread(s) to immediately kill the channel(s) being consumed. Sponsored by: The FreeBSD Foundation MFC after: 2 months PR: 194727 Reviewed by: dev_submerge.ch, bapt, markj Differential Revision: https://reviews.freebsd.org/D43545 (cherry picked from commit 44e128fe9d92c1a544b801cb56e907a66ef34691) --- share/man/man4/snd_uaudio.4 | 11 +---------- sys/dev/sound/pcm/dsp.c | 2 +- sys/dev/sound/pcm/mixer.c | 11 ----------- sys/dev/sound/pcm/sound.c | 24 ++++++++++-------------- sys/dev/sound/usb/uaudio.c | 13 +++---------- 5 files changed, 15 insertions(+), 46 deletions(-) diff --git a/share/man/man4/snd_uaudio.4 b/share/man/man4/snd_uaudio.4 index b6a6c06a231..6e2509b8f2a 100644 --- a/share/man/man4/snd_uaudio.4 +++ b/share/man/man4/snd_uaudio.4 @@ -27,7 +27,7 @@ .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" -.Dd January 29, 2024 +.Dd March 26, 2024 .Dt SND_UAUDIO 4 .Os .Sh NAME @@ -156,15 +156,6 @@ and modified for by .An Hiten Pandya Aq Mt hmp@FreeBSD.org . .Sh BUGS -The PCM framework in -.Fx -only supports synchronous device detach. -That means all mixer and DSP character devices belonging to a given -USB audio device must be closed when receiving an error on a DSP read, -a DSP write or a DSP IOCTL request. -Else the USB audio driver will wait for this to happen, preventing -enumeration of new devices on the parenting USB controller. -.Pp Some USB audio devices might refuse to work properly unless the sample rate is configured the same for both recording and playback, even if only simplex is used. diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c index 003e57446a6..4112e87ba52 100644 --- a/sys/dev/sound/pcm/dsp.c +++ b/sys/dev/sound/pcm/dsp.c @@ -274,7 +274,7 @@ dsp_close(void *data) d = priv->sc; /* At this point pcm_unregister() will destroy all channels anyway. */ - if (!PCM_REGISTERED(d)) + if (PCM_DETACHING(d)) goto skip; PCM_GIANT_ENTER(d); diff --git a/sys/dev/sound/pcm/mixer.c b/sys/dev/sound/pcm/mixer.c index ee1ed11a8ed..cc8cf5b1cee 100644 --- a/sys/dev/sound/pcm/mixer.c +++ b/sys/dev/sound/pcm/mixer.c @@ -817,17 +817,6 @@ mixer_uninit(device_t dev) KASSERT(m->type == MIXER_TYPE_PRIMARY, ("%s(): illegal mixer type=%d", __func__, m->type)); - snd_mtxlock(m->lock); - - if (m->busy) { - snd_mtxunlock(m->lock); - return EBUSY; - } - - /* destroy dev can sleep --hps */ - - snd_mtxunlock(m->lock); - pdev->si_drv1 = NULL; destroy_dev(pdev); diff --git a/sys/dev/sound/pcm/sound.c b/sys/dev/sound/pcm/sound.c index 53cde49c490..1517126210c 100644 --- a/sys/dev/sound/pcm/sound.c +++ b/sys/dev/sound/pcm/sound.c @@ -1001,26 +1001,22 @@ pcm_unregister(device_t dev) CHN_FOREACH(ch, d, channels.pcm) { CHN_LOCK(ch); - if (ch->refcount > 0) { - device_printf(dev, - "unregister: channel %s busy (pid %d)\n", - ch->name, ch->pid); - CHN_UNLOCK(ch); - PCM_RELEASE_QUICK(d); - return (EBUSY); + if (ch->flags & CHN_F_SLEEPING) { + /* + * We are detaching, so do not wait for the timeout in + * chn_read()/chn_write(). Wake up the thread and kill + * the channel immediately. + */ + CHN_BROADCAST(&ch->intr_cv); + ch->flags |= CHN_F_DEAD; } + chn_abort(ch); CHN_UNLOCK(ch); } dsp_destroy_dev(dev); - if (mixer_uninit(dev) == EBUSY) { - device_printf(dev, "unregister: mixer busy\n"); - PCM_LOCK(d); - PCM_RELEASE(d); - PCM_UNLOCK(d); - return (EBUSY); - } + (void)mixer_uninit(dev); /* remove /dev/sndstat entry first */ sndstat_unregister(dev); diff --git a/sys/dev/sound/usb/uaudio.c b/sys/dev/sound/usb/uaudio.c index 5d7396c527e..2351c252202 100644 --- a/sys/dev/sound/usb/uaudio.c +++ b/sys/dev/sound/usb/uaudio.c @@ -1255,20 +1255,13 @@ uaudio_detach_sub(device_t dev) unsigned i = uaudio_get_child_index_by_dev(sc, dev); int error = 0; -repeat: if (sc->sc_child[i].pcm_registered) { error = pcm_unregister(dev); - } else { - if (sc->sc_child[i].mixer_init) - error = mixer_uninit(dev); + } else if (sc->sc_child[i].mixer_init) { + error = mixer_uninit(dev); } - if (error) { - device_printf(dev, "Waiting for sound application to exit!\n"); - usb_pause_mtx(NULL, 2 * hz); - goto repeat; /* try again */ - } - return (0); /* success */ + return (error); } static int