linux/sound/pci/hda/hda_cs_dsp_ctl.h
Richard Fitzgerald 2176c6b599 ALSA: hda/cs_dsp_ctl: Fix mutex inversion when creating controls
Redesign the creation of ALSA controls so that the cs_dsp
pwr_lock is not held when calling snd_ctl_add(). Instead of
creating the ALSA control from the cs_dsp control_add callback,
do it after cs_dsp_power_up() has completed. The existing
functions are changed to return void instead of passing errors
back - this duplicates the original behaviour, as cs_dsp does
not abort firmware load if creation of a control fails.

It is safe to walk the control list without taking any mutex
provided that the caller is not trying to load a new firmware
or remove the driver in parallel. There is no other situation
that the list can change. So the caller can trigger creation
of ALSA controls after cs_dsp_power_up() has returned. A cs_dsp
control will have a non-NULL priv pointer if we have created
an ALSA control.

With the previous code the ALSA controls were created from
the cs_dsp control_add callback. But this is called with
pwr_lock held (as it is part of the DSP power-up sequence).
The kernel lock checking will show a mutex inversion between
this and the control creation path:

control_add
  pwr_lock held, takes controls_rwsem (in snd_ctl_add)

get/put
  controls_rwsem held, takes pwr_lock to call cs_dsp.

This is not completely theoretical. Although the time window
is very small, it is possible for these to run in parallel
and deadlock the old implementation.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20221011143552.621792-4-sbinding@opensource.cirrus.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2022-10-12 08:02:47 +02:00

40 lines
1.0 KiB
C

/* SPDX-License-Identifier: GPL-2.0
*
* HDA DSP ALSA Control Driver
*
* Copyright 2022 Cirrus Logic, Inc.
*
* Author: Stefan Binding <sbinding@opensource.cirrus.com>
*/
#ifndef __HDA_CS_DSP_CTL_H__
#define __HDA_CS_DSP_CTL_H__
#include <sound/soc.h>
#include <linux/firmware/cirrus/cs_dsp.h>
enum hda_cs_dsp_fw_id {
HDA_CS_DSP_FW_SPK_PROT,
HDA_CS_DSP_FW_SPK_CALI,
HDA_CS_DSP_FW_SPK_DIAG,
HDA_CS_DSP_FW_MISC,
HDA_CS_DSP_NUM_FW
};
struct hda_cs_dsp_ctl_info {
struct snd_card *card;
enum hda_cs_dsp_fw_id fw_type;
const char *device_name;
};
extern const char * const hda_cs_dsp_fw_ids[HDA_CS_DSP_NUM_FW];
void hda_cs_dsp_add_controls(struct cs_dsp *dsp, const struct hda_cs_dsp_ctl_info *info);
void hda_cs_dsp_control_remove(struct cs_dsp_coeff_ctl *cs_ctl);
int hda_cs_dsp_write_ctl(struct cs_dsp *dsp, const char *name, int type,
unsigned int alg, const void *buf, size_t len);
int hda_cs_dsp_read_ctl(struct cs_dsp *dsp, const char *name, int type,
unsigned int alg, void *buf, size_t len);
#endif /*__HDA_CS_DSP_CTL_H__*/