From becf9e5d553c2389d857a3c178ce80fdb34a02e1 Mon Sep 17 00:00:00 2001 From: Takashi Sakamoto Date: Sun, 20 Aug 2017 13:49:07 +0900 Subject: [PATCH] ALSA: control: code refactoring for ELEM_READ/ELEM_WRITE operations ALSA control core handles ELEM_READ/ELEM_WRITE requests within lock acquisition of a counting semaphore. The lock is acquired in helper functions in the end of call path before calling implementations of each driver. ioctl(2) with SNDRV_CTL_ELEM_READ ... ->snd_ctl_ioctl() ->snd_ctl_elem_read_user() ->snd_ctl_elem_read() ->down_read(controls_rwsem) ->snd_ctl_find_id() ->struct snd_kcontrol.get() ->up_read(controls_rwsem) ioctl(2) with SNDRV_CTL_ELEM_WRITE ... ->snd_ctl_ioctl() ->snd_ctl_elem_write_user() ->snd_ctl_elem_write() ->down_read(controls_rwsem) ->snd_ctl_find_id() ->struct snd_kcontrol.put() ->up_read(controls_rwsem) This commit moves the lock acquisition to middle of the call graph to simplify the helper functions. As a result: ioctl(2) with SNDRV_CTL_ELEM_READ ... ->snd_ctl_ioctl() ->snd_ctl_elem_read_user() ->down_read(controls_rwsem) ->snd_ctl_elem_read() ->snd_ctl_find_id() ->struct snd_kcontrol.get() ->up_read(controls_rwsem) ioctl(2) with SNDRV_CTL_ELEM_WRITE ... ->snd_ctl_ioctl() ->snd_ctl_elem_write_user() ->down_read(controls_rwsem) ->snd_ctl_elem_write() ->snd_ctl_find_id() ->struct snd_kcontrol.put() ->up_read(controls_rwsem) Signed-off-by: Takashi Sakamoto Signed-off-by: Takashi Iwai --- sound/core/control.c | 77 ++++++++++++++++++++++---------------------- 1 file changed, 38 insertions(+), 39 deletions(-) diff --git a/sound/core/control.c b/sound/core/control.c index 79fdb366ac8d..1c1fc0898afb 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -881,24 +881,18 @@ static int snd_ctl_elem_read(struct snd_card *card, struct snd_kcontrol *kctl; struct snd_kcontrol_volatile *vd; unsigned int index_offset; - int result; - down_read(&card->controls_rwsem); kctl = snd_ctl_find_id(card, &control->id); - if (kctl == NULL) { - result = -ENOENT; - } else { - index_offset = snd_ctl_get_ioff(kctl, &control->id); - vd = &kctl->vd[index_offset]; - if ((vd->access & SNDRV_CTL_ELEM_ACCESS_READ) && - kctl->get != NULL) { - snd_ctl_build_ioff(&control->id, kctl, index_offset); - result = kctl->get(kctl, control); - } else - result = -EPERM; - } - up_read(&card->controls_rwsem); - return result; + if (kctl == NULL) + return -ENOENT; + + index_offset = snd_ctl_get_ioff(kctl, &control->id); + vd = &kctl->vd[index_offset]; + if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) && kctl->get == NULL) + return -EPERM; + + snd_ctl_build_ioff(&control->id, kctl, index_offset); + return kctl->get(kctl, control); } static int snd_ctl_elem_read_user(struct snd_card *card, @@ -913,8 +907,11 @@ static int snd_ctl_elem_read_user(struct snd_card *card, snd_power_lock(card); result = snd_power_wait(card, SNDRV_CTL_POWER_D0); - if (result >= 0) + if (result >= 0) { + down_read(&card->controls_rwsem); result = snd_ctl_elem_read(card, control); + up_read(&card->controls_rwsem); + } snd_power_unlock(card); if (result >= 0) if (copy_to_user(_control, control, sizeof(*control))) @@ -931,29 +928,28 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file, unsigned int index_offset; int result; - down_read(&card->controls_rwsem); kctl = snd_ctl_find_id(card, &control->id); - if (kctl == NULL) { - result = -ENOENT; - } else { - index_offset = snd_ctl_get_ioff(kctl, &control->id); - vd = &kctl->vd[index_offset]; - if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) || - kctl->put == NULL || - (file && vd->owner && vd->owner != file)) { - result = -EPERM; - } else { - snd_ctl_build_ioff(&control->id, kctl, index_offset); - result = kctl->put(kctl, control); - } - if (result > 0) { - struct snd_ctl_elem_id id = control->id; - snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id); - result = 0; - } + if (kctl == NULL) + return -ENOENT; + + index_offset = snd_ctl_get_ioff(kctl, &control->id); + vd = &kctl->vd[index_offset]; + if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) || kctl->put == NULL || + (file && vd->owner && vd->owner != file)) { + return -EPERM; } - up_read(&card->controls_rwsem); - return result; + + snd_ctl_build_ioff(&control->id, kctl, index_offset); + result = kctl->put(kctl, control); + if (result < 0) + return result; + + if (result > 0) { + struct snd_ctl_elem_id id = control->id; + snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id); + } + + return 0; } static int snd_ctl_elem_write_user(struct snd_ctl_file *file, @@ -970,8 +966,11 @@ static int snd_ctl_elem_write_user(struct snd_ctl_file *file, card = file->card; snd_power_lock(card); result = snd_power_wait(card, SNDRV_CTL_POWER_D0); - if (result >= 0) + if (result >= 0) { + down_read(&card->controls_rwsem); result = snd_ctl_elem_write(card, file, control); + up_read(&card->controls_rwsem); + } snd_power_unlock(card); if (result >= 0) if (copy_to_user(_control, control, sizeof(*control))) -- 2.20.1