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ALSA: control: Optimize locking for look-up

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For a fast look-up of a control element via either numid or name
matching (enabled via CONFIG_SND_CTL_FAST_LOOKUP), a locking isn't
needed at all thanks to Xarray.  OTOH, the locking is still needed for
a slow linked-list traversal, and that's rather a rare case.

In this patch, we reduce the use of locking at snd_ctl_find_*() API
functions, and switch from controls_rwsem to controls_rwlock for
avoiding unnecessary lock inversions.  This also resulted in a nice
cleanup, as *_unlocked() version of snd_ctl_find_*() APIs can be
dropped.

snd_ctl_find_id_mixer_unlocked() is still left just as an alias of
snd_ctl_find_id_mixer(), since soc-card.c has a wrapper and there are
several users.  Once after converting there, we can remove it later.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240809104234.8488-3-tiwai@suse.de
This commit is contained in:
Takashi Iwai 2024-08-09 12:42:30 +02:00
parent f428cc9eac
commit 38ea4c3dc3
6 changed files with 64 additions and 115 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
include/sound/control.h
View File

@ -140,9 +140,7 @@ int snd_ctl_remove_id(struct snd_card * card, struct snd_ctl_elem_id *id);
int snd_ctl_rename_id(struct snd_card * card, struct snd_ctl_elem_id *src_id, struct snd_ctl_elem_id *dst_id);
void snd_ctl_rename(struct snd_card *card, struct snd_kcontrol *kctl, const char *name);
int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id, int active);
struct snd_kcontrol *snd_ctl_find_numid_locked(struct snd_card *card, unsigned int numid);
struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid);
struct snd_kcontrol *snd_ctl_find_id_locked(struct snd_card *card, const struct snd_ctl_elem_id *id);
struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card, const struct snd_ctl_elem_id *id);
/**
@ -167,27 +165,11 @@ snd_ctl_find_id_mixer(struct snd_card *card, const char *name)
return snd_ctl_find_id(card, &id);
}
/**
* snd_ctl_find_id_mixer_locked - find the control instance with the given name string
* @card: the card instance
* @name: the name string
*
* Finds the control instance with the given name and
* @SNDRV_CTL_ELEM_IFACE_MIXER. Other fields are set to zero.
*
* This is merely a wrapper to snd_ctl_find_id_locked().
* The caller must down card->controls_rwsem before calling this function.
*
* Return: The pointer of the instance if found, or %NULL if not.
*/
/* to be removed */
static inline struct snd_kcontrol *
snd_ctl_find_id_mixer_locked(struct snd_card *card, const char *name)
{
struct snd_ctl_elem_id id = {};
id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
strscpy(id.name, name, sizeof(id.name));
return snd_ctl_find_id_locked(card, &id);
return snd_ctl_find_id_mixer(card, name);
}
int snd_ctl_create(struct snd_card *card);

2
include/sound/core.h
View File

@ -99,7 +99,7 @@ struct snd_card {
struct device *ctl_dev; /* control device */
unsigned int last_numid; /* last used numeric ID */
struct rw_semaphore controls_rwsem; /* controls lock (list and values) */
rwlock_t controls_rwlock; /* lock for ctl_files list */
rwlock_t controls_rwlock; /* lock for lookup and ctl_files list */
int controls_count; /* count of all controls */
size_t user_ctl_alloc_size; // current memory allocation by user controls.
struct list_head controls; /* all controls for this card */

141
sound/core/control.c
View File

@ -470,7 +470,7 @@ static int __snd_ctl_add_replace(struct snd_card *card,
if (id.index > UINT_MAX - kcontrol->count)
return -EINVAL;
old = snd_ctl_find_id_locked(card, &id);
old = snd_ctl_find_id(card, &id);
if (!old) {
if (mode == CTL_REPLACE)
return -EINVAL;
@ -491,10 +491,12 @@ static int __snd_ctl_add_replace(struct snd_card *card,
if (snd_ctl_find_hole(card, kcontrol->count) < 0)
return -ENOMEM;
list_add_tail(&kcontrol->list, &card->controls);
card->controls_count += kcontrol->count;
kcontrol->id.numid = card->last_numid + 1;
card->last_numid += kcontrol->count;
scoped_guard(write_lock_irq, &card->controls_rwlock) {
list_add_tail(&kcontrol->list, &card->controls);
card->controls_count += kcontrol->count;
kcontrol->id.numid = card->last_numid + 1;
card->last_numid += kcontrol->count;
}
add_hash_entries(card, kcontrol);
@ -579,12 +581,15 @@ static int __snd_ctl_remove(struct snd_card *card,
if (snd_BUG_ON(!card || !kcontrol))
return -EINVAL;
list_del(&kcontrol->list);
if (remove_hash)
remove_hash_entries(card, kcontrol);
card->controls_count -= kcontrol->count;
scoped_guard(write_lock_irq, &card->controls_rwlock) {
list_del(&kcontrol->list);
card->controls_count -= kcontrol->count;
}
for (idx = 0; idx < kcontrol->count; idx++)
snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_REMOVE, kcontrol, idx);
snd_ctl_free_one(kcontrol);
@ -634,7 +639,7 @@ int snd_ctl_remove_id(struct snd_card *card, struct snd_ctl_elem_id *id)
struct snd_kcontrol *kctl;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, id);
kctl = snd_ctl_find_id(card, id);
if (kctl == NULL)
return -ENOENT;
return snd_ctl_remove_locked(card, kctl);
@ -659,7 +664,7 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file,
int idx;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, id);
kctl = snd_ctl_find_id(card, id);
if (kctl == NULL)
return -ENOENT;
if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_USER))
@ -691,7 +696,7 @@ int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
int ret;
down_write(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, id);
kctl = snd_ctl_find_id(card, id);
if (kctl == NULL) {
ret = -ENOENT;
goto unlock;
@ -745,7 +750,7 @@ int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id,
int saved_numid;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, src_id);
kctl = snd_ctl_find_id(card, src_id);
if (kctl == NULL)
return -ENOENT;
saved_numid = kctl->id.numid;
@ -787,6 +792,7 @@ snd_ctl_find_numid_slow(struct snd_card *card, unsigned int numid)
{
struct snd_kcontrol *kctl;
guard(read_lock_irqsave)(&card->controls_rwlock);
list_for_each_entry(kctl, &card->controls, list) {
if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
return kctl;
@ -795,32 +801,6 @@ snd_ctl_find_numid_slow(struct snd_card *card, unsigned int numid)
}
#endif /* !CONFIG_SND_CTL_FAST_LOOKUP */
/**
* snd_ctl_find_numid_locked - find the control instance with the given number-id
* @card: the card instance
* @numid: the number-id to search
*
* Finds the control instance with the given number-id from the card.
*
* The caller must down card->controls_rwsem before calling this function
* (if the race condition can happen).
*
* Return: The pointer of the instance if found, or %NULL if not.
*/
struct snd_kcontrol *
snd_ctl_find_numid_locked(struct snd_card *card, unsigned int numid)
{
if (snd_BUG_ON(!card || !numid))
return NULL;
lockdep_assert_held(&card->controls_rwsem);
#ifdef CONFIG_SND_CTL_FAST_LOOKUP
return xa_load(&card->ctl_numids, numid);
#else
return snd_ctl_find_numid_slow(card, numid);
#endif
}
EXPORT_SYMBOL(snd_ctl_find_numid_locked);
/**
* snd_ctl_find_numid - find the control instance with the given number-id
* @card: the card instance
@ -830,54 +810,22 @@ EXPORT_SYMBOL(snd_ctl_find_numid_locked);
*
* Return: The pointer of the instance if found, or %NULL if not.
*
* Note that this function takes card->controls_rwsem lock internally.
* Note that this function takes card->controls_rwlock lock internally.
*/
struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card,
unsigned int numid)
{
guard(rwsem_read)(&card->controls_rwsem);
return snd_ctl_find_numid_locked(card, numid);
if (snd_BUG_ON(!card || !numid))
return NULL;
#ifdef CONFIG_SND_CTL_FAST_LOOKUP
return xa_load(&card->ctl_numids, numid);
#else
return snd_ctl_find_numid_slow(card, numid);
#endif
}
EXPORT_SYMBOL(snd_ctl_find_numid);
/**
* snd_ctl_find_id_locked - find the control instance with the given id
* @card: the card instance
* @id: the id to search
*
* Finds the control instance with the given id from the card.
*
* The caller must down card->controls_rwsem before calling this function
* (if the race condition can happen).
*
* Return: The pointer of the instance if found, or %NULL if not.
*/
struct snd_kcontrol *snd_ctl_find_id_locked(struct snd_card *card,
const struct snd_ctl_elem_id *id)
{
struct snd_kcontrol *kctl;
if (snd_BUG_ON(!card || !id))
return NULL;
lockdep_assert_held(&card->controls_rwsem);
if (id->numid != 0)
return snd_ctl_find_numid_locked(card, id->numid);
#ifdef CONFIG_SND_CTL_FAST_LOOKUP
kctl = xa_load(&card->ctl_hash, get_ctl_id_hash(id));
if (kctl && elem_id_matches(kctl, id))
return kctl;
if (!card->ctl_hash_collision)
return NULL; /* we can rely on only hash table */
#endif
/* no matching in hash table - try all as the last resort */
list_for_each_entry(kctl, &card->controls, list)
if (elem_id_matches(kctl, id))
return kctl;
return NULL;
}
EXPORT_SYMBOL(snd_ctl_find_id_locked);
/**
* snd_ctl_find_id - find the control instance with the given id
* @card: the card instance
@ -887,13 +835,32 @@ EXPORT_SYMBOL(snd_ctl_find_id_locked);
*
* Return: The pointer of the instance if found, or %NULL if not.
*
* Note that this function takes card->controls_rwsem lock internally.
* Note that this function takes card->controls_rwlock lock internally.
*/
struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
const struct snd_ctl_elem_id *id)
{
guard(rwsem_read)(&card->controls_rwsem);
return snd_ctl_find_id_locked(card, id);
struct snd_kcontrol *kctl;
if (snd_BUG_ON(!card || !id))
return NULL;
if (id->numid != 0)
return snd_ctl_find_numid(card, id->numid);
#ifdef CONFIG_SND_CTL_FAST_LOOKUP
kctl = xa_load(&card->ctl_hash, get_ctl_id_hash(id));
if (kctl && elem_id_matches(kctl, id))
return kctl;
if (!card->ctl_hash_collision)
return NULL; /* we can rely on only hash table */
#endif
/* no matching in hash table - try all as the last resort */
guard(read_lock_irqsave)(&card->controls_rwlock);
list_for_each_entry(kctl, &card->controls, list)
if (elem_id_matches(kctl, id))
return kctl;
return NULL;
}
EXPORT_SYMBOL(snd_ctl_find_id);
@ -1199,7 +1166,7 @@ static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
struct snd_kcontrol *kctl;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, &info->id);
kctl = snd_ctl_find_id(card, &info->id);
if (!kctl)
return -ENOENT;
return __snd_ctl_elem_info(card, kctl, info, ctl);
@ -1235,7 +1202,7 @@ static int snd_ctl_elem_read(struct snd_card *card,
int ret;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, &control->id);
kctl = snd_ctl_find_id(card, &control->id);
if (!kctl)
return -ENOENT;
@ -1303,7 +1270,7 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
int result;
down_write(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, &control->id);
kctl = snd_ctl_find_id(card, &control->id);
if (kctl == NULL) {
up_write(&card->controls_rwsem);
return -ENOENT;
@ -1381,7 +1348,7 @@ static int snd_ctl_elem_lock(struct snd_ctl_file *file,
if (copy_from_user(&id, _id, sizeof(id)))
return -EFAULT;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, &id);
kctl = snd_ctl_find_id(card, &id);
if (!kctl)
return -ENOENT;
vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
@ -1402,7 +1369,7 @@ static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
if (copy_from_user(&id, _id, sizeof(id)))
return -EFAULT;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, &id);
kctl = snd_ctl_find_id(card, &id);
if (!kctl)
return -ENOENT;
vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
@ -1903,7 +1870,7 @@ static int snd_ctl_tlv_ioctl(struct snd_ctl_file *file,
container_size = header.length;
container = buf->tlv;
kctl = snd_ctl_find_numid_locked(file->card, header.numid);
kctl = snd_ctl_find_numid(file->card, header.numid);
if (kctl == NULL)
return -ENOENT;

2
sound/core/control_compat.c
View File

@ -168,7 +168,7 @@ static int get_ctl_type(struct snd_card *card, struct snd_ctl_elem_id *id,
int err;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, id);
kctl = snd_ctl_find_id(card, id);
if (!kctl)
return -ENOENT;
info = kzalloc(sizeof(*info), GFP_KERNEL);

2
sound/core/control_led.c
View File

@ -254,7 +254,7 @@ static int snd_ctl_led_set_id(int card_number, struct snd_ctl_elem_id *id,
if (!card)
return -ENXIO;
guard(rwsem_write)(&card->controls_rwsem);
kctl = snd_ctl_find_id_locked(card, id);
kctl = snd_ctl_find_id(card, id);
if (!kctl)
return -ENOENT;
ioff = snd_ctl_get_ioff(kctl, id);

10
sound/core/oss/mixer_oss.c
View File

@ -510,7 +510,7 @@ static struct snd_kcontrol *snd_mixer_oss_test_id(struct snd_mixer_oss *mixer, c
id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
strscpy(id.name, name, sizeof(id.name));
id.index = index;
return snd_ctl_find_id_locked(card, &id);
return snd_ctl_find_id(card, &id);
}
static void snd_mixer_oss_get_volume1_vol(struct snd_mixer_oss_file *fmixer,
@ -526,7 +526,7 @@ static void snd_mixer_oss_get_volume1_vol(struct snd_mixer_oss_file *fmixer,
if (numid == ID_UNKNOWN)
return;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_numid_locked(card, numid);
kctl = snd_ctl_find_numid(card, numid);
if (!kctl)
return;
uinfo = kzalloc(sizeof(*uinfo), GFP_KERNEL);
@ -559,7 +559,7 @@ static void snd_mixer_oss_get_volume1_sw(struct snd_mixer_oss_file *fmixer,
if (numid == ID_UNKNOWN)
return;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_numid_locked(card, numid);
kctl = snd_ctl_find_numid(card, numid);
if (!kctl)
return;
uinfo = kzalloc(sizeof(*uinfo), GFP_KERNEL);
@ -619,7 +619,7 @@ static void snd_mixer_oss_put_volume1_vol(struct snd_mixer_oss_file *fmixer,
if (numid == ID_UNKNOWN)
return;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_numid_locked(card, numid);
kctl = snd_ctl_find_numid(card, numid);
if (!kctl)
return;
uinfo = kzalloc(sizeof(*uinfo), GFP_KERNEL);
@ -656,7 +656,7 @@ static void snd_mixer_oss_put_volume1_sw(struct snd_mixer_oss_file *fmixer,
if (numid == ID_UNKNOWN)
return;
guard(rwsem_read)(&card->controls_rwsem);
kctl = snd_ctl_find_numid_locked(card, numid);
kctl = snd_ctl_find_numid(card, numid);
if (!kctl)
return;
uinfo = kzalloc(sizeof(*uinfo), GFP_KERNEL);