In ALSA control interface, applications can execute two types of request
for value of members on each element; ELEM_READ and ELEM_WRITE. In ALSA
control core, these two requests are handled within read lock of a
counting semaphore, therefore several processes can run to execute these
two requests at the same time. This has an issue because ELEM_WRITE
requests have an effect to change state of the target element. Concurrent
access should be controlled for each of ELEM_READ/ELEM_WRITE case.
This commit uses the counting semaphore as write lock for ELEM_WRITE
requests, while use it as read lock for ELEM_READ requests. The state of
a target element is maintained exclusively between ELEM_WRITE/ELEM_READ
operations.
There's a concern. If the counting semaphore is acquired for read lock
in implementations of 'struct snd_kcontrol.put()' in each driver, this
commit shall cause dead lock. As of v4.13-rc5, 'snd-mixer-oss.ko',
'snd-emu10k1.ko' and 'snd-soc-sst-atom-hifi2-platform.ko' includes codes
for read locks, but these are not in a call graph from
'struct snd_kcontrol.put(). Therefore, this commit is safe.
In current implementation, the same solution is applied for the other
operations to element; e.g. ELEM_LOCK and ELEM_UNLOCK. There's another
discussion about an overhead to maintain concurrent access to an element
during operating the other elements on the same card instance, because the
lock primitive is originally implemented to maintain a list of elements on
the card instance. There's a substantial difference between
per-element-list lock and per-element lock.
Here, let me investigate another idea to add per-element lock to maintain
the concurrent accesses with inquiry/change requests to an element. It's
not so frequent for applications to operate members on elements, while
adding a new lock primitive to structure increases memory footprint for
all of element sets somehow. Experimentally, inquiry operation is more
frequent than change operation and usage of counting semaphore for the
inquiry operation brings no blocking to the other inquiry operations. Thus
the overhead is not so critical for usual applications. For the above
reasons, in this commit, the per-element lock is not introduced.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Any control event is queued by a call of snd_ctl_notify(). This function
adds the event to each queue of opened file data corresponding to ALSA
control character devices. This function acquired two types of lock; a
counting semaphore for a list of the opened file data and a spinlock for
card data opened by the file. Typically, this function is called after
acquiring a counting semaphore for a list of elements in the card data.
In current implementation of a handler for ELEM_WRITE request, the
function is called after releasing the semaphore for a list of elements
in the card data. This release is not necessarily needed.
This commit removes the release to call the function within the critical
section so that later commits are simple.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make this const as it is only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make this const as it is only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make this const as it is only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make this const as it is only used in a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_card_device_id are not supposed to change at runtime. All functions
working with pnp_card_device_id provided by <linux/pnp.h> work with
const pnp_card_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
*_device_id are not supposed to change at runtime. All functions
working with *_device_id provided by <linux/pnp.h> work with
const *_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
*_device_id are not supposed to change at runtime. All functions
working with *_device_id provided by <linux/pnp.h> work with
const *_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
pnp_device_id are not supposed to change at runtime. All functions
working with pnp_device_id provided by <linux/pnp.h> work with
const pnp_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only passed as the 3rd argument to the
function snd_hda_gen_add_kctl, which is of type const.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used during a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Make these const as they are only used during a copy operation.
Done using Coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
These snd_rawmidi_ops structures are only passed as the third
argument of snd_rawmidi_set_ops. This argument is const, so the
snd_rawmidi_ops structures can be const too.
Done with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
The structure emu8000_ops is only copied into another structure, so
it can be const.
Done with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Add a jump target so that a bit of exception handling can be better reused
in these functions.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
