@@ -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)))
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 <o-takashi@sakamocchi.jp> --- sound/core/control.c | 77 ++++++++++++++++++++++++++-------------------------- 1 file changed, 38 insertions(+), 39 deletions(-)