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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 21 Mar 2018 21:24:50 +0200
Message-ID: <CAHp75VcwFRVX7RTSWv2R_7Hr=gzrwK1aJA8Unypx6zQ49neGjA@mail.gmail.com>
Subject: Re: [PATCH v3] staging: bcm2835-audio: Release resources on module_exit()
To:     Kirill Marinushkin <k.marinushkin@gmail.com>
Cc:     Eric Anholt <eric@anholt.net>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
        Michael Zoran <mzoran@crowfest.net>,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        devel@driverdev.osuosl.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Mar 21, 2018 at 8:48 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
> ~~~~
>

Sorry, just noticed that devm part doesn't make sense after your patch
and misleading.
So, after addressing it, FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

P.S. I didn't get why do you need an empty ->remove() stub. Doesn't
work without it?

> 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: 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  | 57 ++++++++++++----------
>  1 file changed, 30 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.c
> index 8f2d508183b2..125efc55ecb9 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_devm_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_devm_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)
> -{
> -       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;
>  }
> @@ -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;
> @@ -414,6 +410,12 @@ static int snd_bcm2835_alsa_probe_dt(struct platform_device *pdev)
>         return 0;
>  }
>
> +static int snd_bcm2835_alsa_remove(struct platform_device *pdev)
> +{
> +       /* trigger snd_devm_unregister_child() */
> +       return 0;
> +}
> +
>  #ifdef CONFIG_PM
>
>  static int snd_bcm2835_alsa_suspend(struct platform_device *pdev,
> @@ -437,6 +439,7 @@ MODULE_DEVICE_TABLE(of, snd_bcm2835_of_match_table);
>
>  static struct platform_driver bcm2835_alsa0_driver = {
>         .probe = snd_bcm2835_alsa_probe_dt,
> +       .remove = snd_bcm2835_alsa_remove,
>  #ifdef CONFIG_PM
>         .suspend = snd_bcm2835_alsa_suspend,
>         .resume = snd_bcm2835_alsa_resume,
> --
> 2.13.6
>


-- 
With Best Regards,
Andy Shevchenko