ALSA: control: obsolete user_ctl_lock

At a previous commit, concurrent requests for TLV data are maintained
exclusively between read requests and write/command requests. TLV
callback handlers in each driver has no risk from concurrent access for
reference/change.

In current implementation, 'struct snd_card' has a mutex to control
concurrent accesses to user-defined element sets. This commit obsoletes it.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 13 insertions, 25 deletions

diff --git a/sound/core/control.c b/sound/core/control.c
index f3bd9bdba9a7..989292fe33c2 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1095,9 +1095,7 @@ static int snd_ctl_elem_user_get(struct snd_kcontrol *kcontrol,
         char *src = ue->elem_data +
                         snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;
 
-        mutex_lock(&ue->card->user_ctl_lock);
         memcpy(&ucontrol->value, src, size);
-        mutex_unlock(&ue->card->user_ctl_lock);
         return 0;
 }
 
@@ -1110,11 +1108,9 @@ static int snd_ctl_elem_user_put(struct snd_kcontrol *kcontrol,
         char *dst = ue->elem_data +
                         snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;
 
-        mutex_lock(&ue->card->user_ctl_lock);
         change = memcmp(&ucontrol->value, dst, size) != 0;
         if (change)
                 memcpy(dst, &ucontrol->value, size);
-        mutex_unlock(&ue->card->user_ctl_lock);
         return change;
 }
 
@@ -1124,44 +1120,37 @@ static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
                                  unsigned int __user *tlv)
 {
         struct user_element *ue = kcontrol->private_data;
-        int change = 0;
-        void *new_data;
 
         if (op_flag == SNDRV_CTL_TLV_OP_WRITE) {
+                int change;
+                void *new_data;
+
                 if (size > 1024 * 128)  /* sane value */
                         return -EINVAL;
 
                 new_data = memdup_user(tlv, size);
                 if (IS_ERR(new_data))
                         return PTR_ERR(new_data);
-                mutex_lock(&ue->card->user_ctl_lock);
                 change = ue->tlv_data_size != size;
                 if (!change)
                         change = memcmp(ue->tlv_data, new_data, size);
                 kfree(ue->tlv_data);
                 ue->tlv_data = new_data;
                 ue->tlv_data_size = size;
-                mutex_unlock(&ue->card->user_ctl_lock);
+
+                return change;
         } else {
-                int ret = 0;
+                if (!ue->tlv_data_size || !ue->tlv_data)
+                        return -ENXIO;
+
+                if (size < ue->tlv_data_size)
+                        return -ENOSPC;
 
-                mutex_lock(&ue->card->user_ctl_lock);
-                if (!ue->tlv_data_size || !ue->tlv_data) {
-                        ret = -ENXIO;
-                        goto err_unlock;
-                }
-                if (size < ue->tlv_data_size) {
-                        ret = -ENOSPC;
-                        goto err_unlock;
-                }
                 if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))
-                        ret = -EFAULT;
-err_unlock:
-                mutex_unlock(&ue->card->user_ctl_lock);
-                if (ret)
-                        return ret;
+                        return -EFAULT;
+
+                return 0;
         }
-        return change;
 }
 
 static int snd_ctl_elem_init_enum_names(struct user_element *ue)
diff --git a/sound/core/init.c b/sound/core/init.c
index b4365bcf28a7..6e219dc23f96 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -248,7 +248,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
         INIT_LIST_HEAD(&card->devices);
         init_rwsem(&card->controls_rwsem);
         rwlock_init(&card->ctl_files_rwlock);
-        mutex_init(&card->user_ctl_lock);
         INIT_LIST_HEAD(&card->controls);
         INIT_LIST_HEAD(&card->ctl_files);
         spin_lock_init(&card->files_lock);