From: Takashi Iwai tiwai@suse.de
[ Upstream commit fcc62b19104a67b9a2941513771e09389b75bd95 ]
The code path for kcontrol accesses have often nested locks of both card's controls_rwsem and power_ref, and applies in that order. However, what could take much longer is the latter, power_ref; it waits for the power state of the device, and it pretty much depends on the user's action.
This patch swaps the locking order of those locks to a more natural way, namely, power_ref -> controls_rwsem, in order to shorten the time of possible nested locks. For consistency, power_ref is taken always in the top-level caller side (that is, *_user() functions and the ioctl handler itself).
Link: https://patch.msgid.link/20240729160659.4516-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- sound/core/control.c | 54 ++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 20 deletions(-)
diff --git a/sound/core/control.c b/sound/core/control.c index f64a555f404f0..96a2c088a460e 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -1167,9 +1167,7 @@ static int __snd_ctl_elem_info(struct snd_card *card, #ifdef CONFIG_SND_DEBUG info->access = 0; #endif - result = snd_power_ref_and_wait(card); - if (!result) - result = kctl->info(kctl, info); + result = kctl->info(kctl, info); snd_power_unref(card); if (result >= 0) { snd_BUG_ON(info->access); @@ -1208,12 +1206,17 @@ static int snd_ctl_elem_info(struct snd_ctl_file *ctl, static int snd_ctl_elem_info_user(struct snd_ctl_file *ctl, struct snd_ctl_elem_info __user *_info) { + struct snd_card *card = ctl->card; struct snd_ctl_elem_info info; int result;
if (copy_from_user(&info, _info, sizeof(info))) return -EFAULT; + result = snd_power_ref_and_wait(card); + if (result) + return result; result = snd_ctl_elem_info(ctl, &info); + snd_power_unref(card); if (result < 0) return result; /* drop internal access flags */ @@ -1257,10 +1260,7 @@ static int snd_ctl_elem_read(struct snd_card *card,
if (!snd_ctl_skip_validation(&info)) fill_remaining_elem_value(control, &info, pattern); - ret = snd_power_ref_and_wait(card); - if (!ret) - ret = kctl->get(kctl, control); - snd_power_unref(card); + ret = kctl->get(kctl, control); if (ret < 0) return ret; if (!snd_ctl_skip_validation(&info) && @@ -1285,7 +1285,11 @@ static int snd_ctl_elem_read_user(struct snd_card *card, if (IS_ERR(control)) return PTR_ERR(no_free_ptr(control));
+ result = snd_power_ref_and_wait(card); + if (result) + return result; result = snd_ctl_elem_read(card, control); + snd_power_unref(card); if (result < 0) return result;
@@ -1300,7 +1304,7 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file, struct snd_kcontrol *kctl; struct snd_kcontrol_volatile *vd; unsigned int index_offset; - int result; + int result = 0;
down_write(&card->controls_rwsem); kctl = snd_ctl_find_id_locked(card, &control->id); @@ -1318,9 +1322,8 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file, }
snd_ctl_build_ioff(&control->id, kctl, index_offset); - result = snd_power_ref_and_wait(card); /* validate input values */ - if (IS_ENABLED(CONFIG_SND_CTL_INPUT_VALIDATION) && !result) { + if (IS_ENABLED(CONFIG_SND_CTL_INPUT_VALIDATION)) { struct snd_ctl_elem_info info;
memset(&info, 0, sizeof(info)); @@ -1332,7 +1335,6 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file, } if (!result) result = kctl->put(kctl, control); - snd_power_unref(card); if (result < 0) { up_write(&card->controls_rwsem); return result; @@ -1361,7 +1363,11 @@ static int snd_ctl_elem_write_user(struct snd_ctl_file *file, return PTR_ERR(no_free_ptr(control));
card = file->card; + result = snd_power_ref_and_wait(card); + if (result < 0) + return result; result = snd_ctl_elem_write(card, file, control); + snd_power_unref(card); if (result < 0) return result;
@@ -1830,7 +1836,7 @@ static int call_tlv_handler(struct snd_ctl_file *file, int op_flag, {SNDRV_CTL_TLV_OP_CMD, SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND}, }; struct snd_kcontrol_volatile *vd = &kctl->vd[snd_ctl_get_ioff(kctl, id)]; - int i, ret; + int i;
/* Check support of the request for this element. */ for (i = 0; i < ARRAY_SIZE(pairs); ++i) { @@ -1848,11 +1854,7 @@ static int call_tlv_handler(struct snd_ctl_file *file, int op_flag, vd->owner != NULL && vd->owner != file) return -EPERM;
- ret = snd_power_ref_and_wait(file->card); - if (!ret) - ret = kctl->tlv.c(kctl, op_flag, size, buf); - snd_power_unref(file->card); - return ret; + return kctl->tlv.c(kctl, op_flag, size, buf); }
static int read_tlv_buf(struct snd_kcontrol *kctl, struct snd_ctl_elem_id *id, @@ -1965,16 +1967,28 @@ static long snd_ctl_ioctl(struct file *file, unsigned int cmd, unsigned long arg case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS: return snd_ctl_subscribe_events(ctl, ip); case SNDRV_CTL_IOCTL_TLV_READ: - scoped_guard(rwsem_read, &ctl->card->controls_rwsem) + err = snd_power_ref_and_wait(card); + if (err < 0) + return err; + scoped_guard(rwsem_read, &card->controls_rwsem) err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ); + snd_power_unref(card); return err; case SNDRV_CTL_IOCTL_TLV_WRITE: - scoped_guard(rwsem_write, &ctl->card->controls_rwsem) + err = snd_power_ref_and_wait(card); + if (err < 0) + return err; + scoped_guard(rwsem_write, &card->controls_rwsem) err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE); + snd_power_unref(card); return err; case SNDRV_CTL_IOCTL_TLV_COMMAND: - scoped_guard(rwsem_write, &ctl->card->controls_rwsem) + err = snd_power_ref_and_wait(card); + if (err < 0) + return err; + scoped_guard(rwsem_write, &card->controls_rwsem) err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD); + snd_power_unref(card); return err; case SNDRV_CTL_IOCTL_POWER: return -ENOPROTOOPT;