ALSA: echoaudio: Race conditions around "opencount"
Use of atomics does not make these statements robust:
atomic_inc(&chip->opencount);
if (atomic_read(&chip->opencount) > 1 && chip->rate_set)
chip->can_set_rate=0;
and
if (atomic_read(&chip->opencount)) {
if (chip->opencount) {
changed = -EAGAIN;
} else {
changed = set_digital_mode(chip, dmode);
It would be necessary to atomically increment or decrement the value
and use the returned result. And yet we still need to prevent other
threads making use of "can_set_rate" while we set it.
However in all but one case the atomic is misleading as they are already
running with "mode_mutex" held.
Decisions are made on mode setting are often intrinsically connected
to "opencount" because some operations are not permitted unless
there is sole ownership.
So instead simplify this, and use "mode_mutex" as a lock for all reference
counting and mode setting.
Signed-off-by: Mark Hills <mark@xwax.org>
Link: https://lore.kernel.org/r/20200708101848.3457-2-mark@xwax.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Mark Hills
Takashi Iwai
Родитель
db091b0e14
Коммит
027c70021b
|
|
@ -245,13 +245,20 @@ static int hw_rule_sample_rate(struct snd_pcm_hw_params *params,
|
|||
SNDRV_PCM_HW_PARAM_RATE);
|
||||
struct echoaudio *chip = rule->private;
|
||||
struct snd_interval fixed;
|
||||
int err;
|
||||
|
||||
if (!chip->can_set_rate) {
|
||||
mutex_lock(&chip->mode_mutex);
|
||||
|
||||
if (chip->can_set_rate) {
|
||||
err = 0;
|
||||
} else {
|
||||
snd_interval_any(&fixed);
|
||||
fixed.min = fixed.max = chip->sample_rate;
|
||||
return snd_interval_refine(rate, &fixed);
|
||||
err = snd_interval_refine(rate, &fixed);
|
||||
}
|
||||
return 0;
|
||||
|
||||
mutex_unlock(&chip->mode_mutex);
|
||||
return err;
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -322,7 +329,7 @@ static int pcm_open(struct snd_pcm_substream *substream,
|
|||
SNDRV_PCM_HW_PARAM_RATE, -1)) < 0)
|
||||
return err;
|
||||
|
||||
/* Finally allocate a page for the scatter-gather list */
|
||||
/* Allocate a page for the scatter-gather list */
|
||||
if ((err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV,
|
||||
&chip->pci->dev,
|
||||
PAGE_SIZE, &pipe->sgpage)) < 0) {
|
||||
|
|
@ -330,6 +337,17 @@ static int pcm_open(struct snd_pcm_substream *substream,
|
|||
return err;
|
||||
}
|
||||
|
||||
/*
|
||||
* Sole ownership required to set the rate
|
||||
*/
|
||||
|
||||
dev_dbg(chip->card->dev, "pcm_open opencount=%d can_set_rate=%d, rate_set=%d",
|
||||
chip->opencount, chip->can_set_rate, chip->rate_set);
|
||||
|
||||
chip->opencount++;
|
||||
if (chip->opencount > 1 && chip->rate_set)
|
||||
chip->can_set_rate = 0;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -353,12 +371,7 @@ static int pcm_analog_in_open(struct snd_pcm_substream *substream)
|
|||
hw_rule_capture_format_by_channels, NULL,
|
||||
SNDRV_PCM_HW_PARAM_CHANNELS, -1)) < 0)
|
||||
return err;
|
||||
atomic_inc(&chip->opencount);
|
||||
if (atomic_read(&chip->opencount) > 1 && chip->rate_set)
|
||||
chip->can_set_rate=0;
|
||||
dev_dbg(chip->card->dev, "pcm_analog_in_open cs=%d oc=%d r=%d\n",
|
||||
chip->can_set_rate, atomic_read(&chip->opencount),
|
||||
chip->sample_rate);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -388,12 +401,7 @@ static int pcm_analog_out_open(struct snd_pcm_substream *substream)
|
|||
NULL,
|
||||
SNDRV_PCM_HW_PARAM_CHANNELS, -1)) < 0)
|
||||
return err;
|
||||
atomic_inc(&chip->opencount);
|
||||
if (atomic_read(&chip->opencount) > 1 && chip->rate_set)
|
||||
chip->can_set_rate=0;
|
||||
dev_dbg(chip->card->dev, "pcm_analog_out_open cs=%d oc=%d r=%d\n",
|
||||
chip->can_set_rate, atomic_read(&chip->opencount),
|
||||
chip->sample_rate);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -429,10 +437,6 @@ static int pcm_digital_in_open(struct snd_pcm_substream *substream)
|
|||
SNDRV_PCM_HW_PARAM_CHANNELS, -1)) < 0)
|
||||
goto din_exit;
|
||||
|
||||
atomic_inc(&chip->opencount);
|
||||
if (atomic_read(&chip->opencount) > 1 && chip->rate_set)
|
||||
chip->can_set_rate=0;
|
||||
|
||||
din_exit:
|
||||
mutex_unlock(&chip->mode_mutex);
|
||||
return err;
|
||||
|
|
@ -471,9 +475,7 @@ static int pcm_digital_out_open(struct snd_pcm_substream *substream)
|
|||
NULL, SNDRV_PCM_HW_PARAM_CHANNELS,
|
||||
-1)) < 0)
|
||||
goto dout_exit;
|
||||
atomic_inc(&chip->opencount);
|
||||
if (atomic_read(&chip->opencount) > 1 && chip->rate_set)
|
||||
chip->can_set_rate=0;
|
||||
|
||||
dout_exit:
|
||||
mutex_unlock(&chip->mode_mutex);
|
||||
return err;
|
||||
|
|
@ -488,23 +490,29 @@ dout_exit:
|
|||
static int pcm_close(struct snd_pcm_substream *substream)
|
||||
{
|
||||
struct echoaudio *chip = snd_pcm_substream_chip(substream);
|
||||
int oc;
|
||||
|
||||
/* Nothing to do here. Audio is already off and pipe will be
|
||||
* freed by its callback
|
||||
*/
|
||||
|
||||
atomic_dec(&chip->opencount);
|
||||
oc = atomic_read(&chip->opencount);
|
||||
dev_dbg(chip->card->dev, "pcm_close oc=%d cs=%d rs=%d\n", oc,
|
||||
chip->can_set_rate, chip->rate_set);
|
||||
if (oc < 2)
|
||||
chip->can_set_rate = 1;
|
||||
if (oc == 0)
|
||||
chip->rate_set = 0;
|
||||
dev_dbg(chip->card->dev, "pcm_close2 oc=%d cs=%d rs=%d\n", oc,
|
||||
chip->can_set_rate, chip->rate_set);
|
||||
mutex_lock(&chip->mode_mutex);
|
||||
|
||||
dev_dbg(chip->card->dev, "pcm_open opencount=%d can_set_rate=%d, rate_set=%d",
|
||||
chip->opencount, chip->can_set_rate, chip->rate_set);
|
||||
|
||||
chip->opencount--;
|
||||
|
||||
switch (chip->opencount) {
|
||||
case 1:
|
||||
chip->can_set_rate = 1;
|
||||
break;
|
||||
|
||||
case 0:
|
||||
chip->rate_set = 0;
|
||||
break;
|
||||
}
|
||||
|
||||
mutex_unlock(&chip->mode_mutex);
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -1409,7 +1417,7 @@ static int snd_echo_digital_mode_put(struct snd_kcontrol *kcontrol,
|
|||
/* Do not allow the user to change the digital mode when a pcm
|
||||
device is open because it also changes the number of channels
|
||||
and the allowed sample rates */
|
||||
if (atomic_read(&chip->opencount)) {
|
||||
if (chip->opencount) {
|
||||
changed = -EAGAIN;
|
||||
} else {
|
||||
changed = set_digital_mode(chip, dmode);
|
||||
|
|
@ -1874,7 +1882,7 @@ static int snd_echo_create(struct snd_card *card,
|
|||
chip->card = card;
|
||||
chip->pci = pci;
|
||||
chip->irq = -1;
|
||||
atomic_set(&chip->opencount, 0);
|
||||
chip->opencount = 0;
|
||||
mutex_init(&chip->mode_mutex);
|
||||
chip->can_set_rate = 1;
|
||||
} else {
|
||||
|
|
|
|||
|
|
@ -336,7 +336,7 @@ struct echoaudio {
|
|||
struct mutex mode_mutex;
|
||||
u16 num_digital_modes, digital_mode_list[6];
|
||||
u16 num_clock_sources, clock_source_list[10];
|
||||
atomic_t opencount;
|
||||
unsigned int opencount; /* protected by mode_mutex */
|
||||
struct snd_kcontrol *clock_src_ctl;
|
||||
struct snd_pcm *analog_pcm, *digital_pcm;
|
||||
struct snd_card *card;
|
||||
|
|
@ -353,8 +353,8 @@ struct echoaudio {
|
|||
struct timer_list timer;
|
||||
char tinuse; /* Timer in use */
|
||||
char midi_full; /* MIDI output buffer is full */
|
||||
char can_set_rate;
|
||||
char rate_set;
|
||||
char can_set_rate; /* protected by mode_mutex */
|
||||
char rate_set; /* protected by mode_mutex */
|
||||
|
||||
/* This stuff is used mainly by the lowlevel code */
|
||||
struct comm_page *comm_page; /* Virtual address of the memory
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче