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Subject[PATCH v5] staging: bcm2835-audio: Release resources on module_exit()
Date
In the current implementation, `rmmod snd_bcm2835` does not release
resources properly. It causes an oops when trying to list sound devices.

This commit fixes it.

The details WRT allocation / free are described below.

Device structure WRT allocation:

pdev
\childdev[]
\card
\chip
\pcm
\ctl

Allocation / register sequence:

* childdev: devm_kzalloc - freed during driver detach
* childdev: device_initialize - freed during device_unregister
* pdev: devres_alloc - freed during driver detach
* childdev: device_add - removed during device_unregister
* pdev, childdev: devres_add - freed during driver detach
* card: snd_card_new - freed during snd_card_free
* chip: kzalloc - freed during kfree
* card, chip: snd_device_new - freed during snd_device_free
* chip: new_pcm - TODO: free pcm
* chip: new_ctl - TODO: free ctl
* card: snd_card_register - unregistered during snd_card_free

Free / unregister sequence:

* card: snd_card_free
* card, chip: snd_device_free
* childdev: device_unregister
* chip: kfree

Steps to reproduce the issue before this commit:

~~~~
$ rmmod snd_bcm2835
$ aplay -L
[ 138.648130] Unable to handle kernel paging request at virtual address 7f1343c0
[ 138.660415] pgd = ad8f0000
[ 138.665567] [7f1343c0] *pgd=3864c811, *pte=00000000, *ppte=00000000
[ 138.674887] Internal error: Oops: 7 [#1] SMP ARM
[ 138.683571] Modules linked in: sha256_generic cfg80211 rfkill snd_pcm snd_timer
snd fixed uio_pdrv_genirq uio ip_tables x_tables ipv6 [last unloaded: snd_bcm2835
]
[ 138.706594] CPU: 3 PID: 463 Comm: aplay Tainted: G WC 4.15.0-rc1-v
7+ #6
[ 138.719833] Hardware name: BCM2835
[ 138.726016] task: b877ac00 task.stack: aebec000
[ 138.733408] PC is at try_module_get+0x38/0x24c
[ 138.740813] LR is at snd_ctl_open+0x58/0x194 [snd]
[ 138.748485] pc : [<801c4d5c>] lr : [<7f0e6b2c>] psr: 20000013
[ 138.757709] sp : aebedd60 ip : aebedd88 fp : aebedd84
[ 138.765884] r10: 00000000 r9 : 00000004 r8 : 7f0ed440
[ 138.774040] r7 : b7e469b0 r6 : 7f0e6b2c r5 : afd91900 r4 : 7f1343c0
[ 138.783571] r3 : aebec000 r2 : 00000001 r1 : b877ac00 r0 : 7f1343c0
[ 138.793084] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 138.803300] Control: 10c5387d Table: 2d8f006a DAC: 00000055
[ 138.812064] Process aplay (pid: 463, stack limit = 0xaebec210)
[ 138.820868] Stack: (0xaebedd60 to 0xaebee000)
[ 138.828207] dd60: 00000000 b848d000 afd91900 00000000 b7e469b0 7f0ed440 aebedda4 aebedd88
[ 138.842371] dd80: 7f0e6b2c 801c4d30 afd91900 7f0ea4dc 00000000 b7e469b0 aebeddcc aebedda8
[ 138.856611] dda0: 7f0e250c 7f0e6ae0 7f0e2464 b8478ec0 b7e469b0 afd91900 7f0ea388 00000000
[ 138.870864] ddc0: aebeddf4 aebeddd0 802ce590 7f0e2470 8090ab64 afd91900 afd91900 b7e469b0
[ 138.885301] dde0: afd91908 802ce4e4 aebede1c aebeddf8 802c57b4 802ce4f0 afd91900 aebedea8
[ 138.900110] de00: b7fa4c00 00000000 00000000 00000004 aebede3c aebede20 802c6ba8 802c56b4
[ 138.915260] de20: aebedea8 00000000 aebedf5c 00000000 aebedea4 aebede40 802d9a68 802c6b58
[ 138.930661] de40: b874ddd0 00000000 00000000 00000001 00000041 00000000 afd91900 aebede70
[ 138.946402] de60: 00000000 00000000 00000002 b7e469b0 b8a87610 b8d6ab80 801852f8 00080000
[ 138.962314] de80: aebedf5c aebedea8 00000001 80108464 aebec000 00000000 aebedf4c aebedea8
[ 138.978414] dea0: 802dacd4 802d970c b8a87610 b8d6ab80 a7982bc6 00000009 af363019 b9231480
[ 138.994617] dec0: 00000000 b8c038a0 b7e469b0 00000101 00000002 00000238 00000000 00000000
[ 139.010823] dee0: 00000000 aebedee8 00080000 0000000f aebedf3c aebedf00 802ed7e4 80843f94
[ 139.027025] df00: 00000003 00080000 b9231490 b9231480 00000000 00080000 af363000 00000000
[ 139.043229] df20: 00000005 00000002 ffffff9c 00000000 00080000 ffffff9c af363000 00000003
[ 139.059430] df40: aebedf94 aebedf50 802c6f70 802dac70 aebec000 00000000 00000001 00000000
[ 139.075629] df60: 00020000 00000004 00000100 00000001 7ebe577c 0002e038 00000000 00000005
[ 139.091828] df80: 80108464 aebec000 aebedfa4 aebedf98 802c7060 802c6e6c 00000000 aebedfa8
[ 139.108025] dfa0: 801082c0 802c7040 7ebe577c 0002e038 7ebe577c 00080000 00000b98 e81c8400
[ 139.124222] dfc0: 7ebe577c 0002e038 00000000 00000005 7ebe57e4 00a20af8 7ebe57f0 76f87394
[ 139.140419] dfe0: 00000000 7ebe55c4 76ec88e8 76df1d9c 60000010 7ebe577c 00000000 00000000
[ 139.156715] [<801c4d5c>] (try_module_get) from [<7f0e6b2c>] (snd_ctl_open+0x58/0x194 [snd])
[ 139.173222] [<7f0e6b2c>] (snd_ctl_open [snd]) from [<7f0e250c>] (snd_open+0xa8/0x14c [snd])
[ 139.189683] [<7f0e250c>] (snd_open [snd]) from [<802ce590>] (chrdev_open+0xac/0x188)
[ 139.205465] [<802ce590>] (chrdev_open) from [<802c57b4>] (do_dentry_open+0x10c/0x314)
[ 139.221347] [<802c57b4>] (do_dentry_open) from [<802c6ba8>] (vfs_open+0x5c/0x88)
[ 139.236788] [<802c6ba8>] (vfs_open) from [<802d9a68>] (path_openat+0x368/0x944)
[ 139.248270] [<802d9a68>] (path_openat) from [<802dacd4>] (do_filp_open+0x70/0xc4)
[ 139.263731] [<802dacd4>] (do_filp_open) from [<802c6f70>] (do_sys_open+0x110/0x1d4)
[ 139.279378] [<802c6f70>] (do_sys_open) from [<802c7060>] (SyS_open+0x2c/0x30)
[ 139.290647] [<802c7060>] (SyS_open) from [<801082c0>] (ret_fast_syscall+0x0/0x28)
[ 139.306021] Code: e3c3303f e5932004 e2822001 e5832004 (e5943000)
[ 139.316265] ---[ end trace 7f3f7f6193b663ed ]---
[ 139.324956] note: aplay[463] exited with preempt_count 1
~~~~

Signed-off-by: Kirill Marinushkin <k.marinushkin@gmail.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: Michael Zoran <mzoran@crowfest.net>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: linux-rpi-kernel@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: devel@driverdev.osuosl.org
Cc: linux-kernel@vger.kernel.org
---
.../staging/vc04_services/bcm2835-audio/bcm2835.c | 54 ++++++++++------------
1 file changed, 25 insertions(+), 29 deletions(-)

diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c
index 8f2d508183b2..9030d71a3d0b 100644
--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c
+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c
@@ -36,6 +36,10 @@ MODULE_PARM_DESC(enable_compat_alsa,
static void snd_devm_unregister_child(struct device *dev, void *res)
{
struct device *childdev = *(struct device **)res;
+ struct bcm2835_chip *chip = dev_get_drvdata(childdev);
+ struct snd_card *card = chip->card;
+
+ snd_card_free(card);

device_unregister(childdev);
}
@@ -61,6 +65,13 @@ static int snd_devm_add_child(struct device *dev, struct device *child)
return 0;
}

+static void snd_bcm2835_release(struct device *dev)
+{
+ struct bcm2835_chip *chip = dev_get_drvdata(dev);
+
+ kfree(chip);
+}
+
static struct device *
snd_create_device(struct device *parent,
struct device_driver *driver,
@@ -76,6 +87,7 @@ snd_create_device(struct device *parent,
device_initialize(device);
device->parent = parent;
device->driver = driver;
+ device->release = snd_bcm2835_release;

dev_set_name(device, "%s", name);

@@ -86,18 +98,19 @@ snd_create_device(struct device *parent,
return device;
}

-static int snd_bcm2835_free(struct bcm2835_chip *chip)
-{
- kfree(chip);
- return 0;
-}
-
/* component-destructor
* (see "Management of Cards and Components")
*/
static int snd_bcm2835_dev_free(struct snd_device *device)
{
- return snd_bcm2835_free(device->device_data);
+ struct bcm2835_chip *chip = device->device_data;
+ struct snd_card *card = chip->card;
+
+ /* TODO: free pcm, ctl */
+
+ snd_device_free(card, chip);
+
+ return 0;
}

/* chip-specific constructor
@@ -122,7 +135,7 @@ static int snd_bcm2835_create(struct snd_card *card,

err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
if (err) {
- snd_bcm2835_free(chip);
+ kfree(chip);
return err;
}

@@ -130,31 +143,14 @@ static int snd_bcm2835_create(struct snd_card *card,
return 0;
}

-static void snd_devm_card_free(struct device *dev, void *res)
+static struct snd_card *snd_bcm2835_card_new(struct device *dev)
{
- struct snd_card *snd_card = *(struct snd_card **)res;
-
- snd_card_free(snd_card);
-}
-
-static struct snd_card *snd_devm_card_new(struct device *dev)
-{
- struct snd_card **dr;
struct snd_card *card;
int ret;

- dr = devres_alloc(snd_devm_card_free, sizeof(*dr), GFP_KERNEL);
- if (!dr)
- return ERR_PTR(-ENOMEM);
-
ret = snd_card_new(dev, -1, NULL, THIS_MODULE, 0, &card);
- if (ret) {
- devres_free(dr);
+ if (ret)
return ERR_PTR(ret);
- }
-
- *dr = card;
- devres_add(dev, dr);

return card;
}
@@ -271,7 +267,7 @@ static int snd_add_child_device(struct device *device,
return PTR_ERR(child);
}

- card = snd_devm_card_new(child);
+ card = snd_bcm2835_card_new(child);
if (IS_ERR(card)) {
dev_err(child, "Failed to create card");
return PTR_ERR(card);
@@ -313,7 +309,7 @@ static int snd_add_child_device(struct device *device,
return err;
}

- dev_set_drvdata(child, card);
+ dev_set_drvdata(child, chip);
dev_info(child, "card created with %d channels\n", numchans);

return 0;
--
2.13.6
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