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    SubjectRe: [PATCH v5] staging: bcm2835-audio: Release resources on module_exit()
    On Fri, Mar 23, 2018 at 9:32 PM, Kirill Marinushkin
    <k.marinushkin@gmail.com> wrote:
    > 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
    > ~~~~
    >

    FWIW,
    Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

    > 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
    >



    --
    With Best Regards,
    Andy Shevchenko

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