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DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,disroot.org:email,suse.de:dkim] X-Spam-Flag: NO X-Spam-Score: -3.51 On Sun, 11 Oct 2026 20:06:17 +0200, Ali Ahmet Memiš wrote: > > snd_ctl_led_disconnect() removes the ctl-led sysfs files while > holding card->controls_rwsem. Hm, it's not clear to me how this happens: I see no controls_rwsem down around snd_ctl_led_disconnect() call. Could you elaborate about it a bit more? thanks, Takashi > device_unregister() waits for running > sysfs callbacks which can deadlock when a concurrent write causes > the attach or detach callback to wait for controls_rwsem. > > Break kernfs active protection in the attach, detach and list > callbacks and hold a module reference instead. > > Fixes: a135dfb5de15 ("ALSA: led control - add sysfs kcontrol LED marking layer") > Signed-off-by: Ali Ahmet Memiš > --- > sound/core/control_led.c | 62 ++++++++++++++++++++++++++++++++++++---- > 1 file changed, 57 insertions(+), 5 deletions(-) > > diff --git a/sound/core/control_led.c b/sound/core/control_led.c > index ec0e6c7ad..501387287 100644 > --- a/sound/core/control_led.c > +++ b/sound/core/control_led.c > @@ -563,12 +563,43 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si > return count; > } > > +/* > + * snd_ctl_led_disconnect() removes these files with card->controls_rwsem > + * held. so don't let the removal wait for a callback that takes it. > + */ > +static struct kernfs_node *snd_ctl_led_sysfs_enter(struct device *dev, > + struct device_attribute *attr) > +{ > + struct kernfs_node *kn; > + > + if (!try_module_get(THIS_MODULE)) > + return NULL; > + kn = sysfs_break_active_protection(&dev->kobj, &attr->attr); > + if (!kn) > + module_put(THIS_MODULE); > + return kn; > +} > + > +static void snd_ctl_led_sysfs_exit(struct kernfs_node *kn) > +{ > + sysfs_unbreak_active_protection(kn); > + module_put(THIS_MODULE); > +} > + > static ssize_t attach_store(struct device *dev, > struct device_attribute *attr, > const char *buf, size_t count) > { > struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev); > - return set_led_id(led_card, buf, count, true); > + struct kernfs_node *kn; > + ssize_t ret; > + > + kn = snd_ctl_led_sysfs_enter(dev, attr); > + if (!kn) > + return -ENODEV; > + ret = set_led_id(led_card, buf, count, true); > + snd_ctl_led_sysfs_exit(kn); > + return ret; > } > > static ssize_t detach_store(struct device *dev, > @@ -576,7 +607,15 @@ static ssize_t detach_store(struct device *dev, > const char *buf, size_t count) > { > struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev); > - return set_led_id(led_card, buf, count, false); > + struct kernfs_node *kn; > + ssize_t ret; > + > + kn = snd_ctl_led_sysfs_enter(dev, attr); > + if (!kn) > + return -ENODEV; > + ret = set_led_id(led_card, buf, count, false); > + snd_ctl_led_sysfs_exit(kn); > + return ret; > } > > static ssize_t reset_store(struct device *dev, > @@ -594,10 +633,8 @@ static ssize_t reset_store(struct device *dev, > return count; > } > > -static ssize_t list_show(struct device *dev, > - struct device_attribute *attr, char *buf) > +static ssize_t snd_ctl_led_list(struct snd_ctl_led_card *led_card, char *buf) > { > - struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev); > struct snd_ctl_led_ctl *lctl; > size_t l = 0; > struct snd_card *card __free(snd_card_unref) = > @@ -620,6 +657,21 @@ static ssize_t list_show(struct device *dev, > return l; > } > > +static ssize_t list_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev); > + struct kernfs_node *kn; > + ssize_t ret; > + > + kn = snd_ctl_led_sysfs_enter(dev, attr); > + if (!kn) > + return -ENODEV; > + ret = snd_ctl_led_list(led_card, buf); > + snd_ctl_led_sysfs_exit(kn); > + return ret; > +} > + > static DEVICE_ATTR_WO(attach); > static DEVICE_ATTR_WO(detach); > static DEVICE_ATTR_WO(reset); > -- > 2.55.0 >