Re: [PATCH] PM / clock_ops: Fix crash in clocks management code if !CONFIG_PM_RUNTIME

[Geert Uytterhoeven]

Upstream commit a968bed78b549b4c61d4a46e59161fc1f60f96a6
Author: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Date:   Wed Oct 1 20:38:17 2014 +0200

    PM / clk: Fix crash in clocks management code if !CONFIG_PM_RUNTIME


Simon tried it on mackerel. It did not crash, but caused a warning and
backtrace:

    WARNING: CPU: 0 PID: 1420 at drivers/sh/clk/core.c:240
__clk_disable+0x80/0x90()
    Trying to disable clock c04bd4d8 with 0 usecount

which got fixed by the patch. So I think it should be applied to
-stable (v3.14 and up).

Thanks!

On Wed, Oct 1, 2014 at 8:38 PM, Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
> Unlike the clocks management code for runtime PM, the code used for
> system suspend does not check the pm_clock_entry.status field.
> If pm_clk_acquire() failed, ce->status will be PCE_STATUS_ERROR, and
> ce->clk will be a negative error code (e.g. 0xfffffffe = -2 = -ENOENT).
>
> Depending on the clock implementation, suspend or resume may crash with:
>
>     Unable to handle kernel NULL pointer dereference at virtual address 00000026
>
> (CCF clk_disable() has an IS_ERR_OR_NULL() check, while CCF clk_enable()
>  only has a NULL check; pre-CCF implementations may behave differently)
>
> While just checking for PCE_STATUS_ERROR would be sufficient, it doesn't
> hurt to use the same state machine as is done for runtime PM, as this
> makes the two versions more similar, and eligible for a future
> consolidation.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> This crash started to happen on armadillo-legacy during s2ram if
> CONFIG_PM_RUNTIME is not set after applying "[PATCH v2 07/11] ARM:
> shmobile: r8a7740/armadillo legacy: Add A4MP pm domain support"
> (http://www.spinics.net/linux/lists/arm-kernel/msg365438.html), as
> there's no NULL clock for the HDMI device.
>
> Most existing code calling pm_clk_suspend()/pm_clk_resume() is protected
> by a check for CONFIG_PM_RUNTIME (davinci, keystone, omap1,
> drivers/sh/pm_runtime.c), so it was not affected by this bug.
>
> Exceptions are:
>   - arch/arm/mach-shmobile/pm-r8a7779.c (marzen),
>   - arch/arm/mach-shmobile/pm-rmobile.c (r8a7740/armadillo and
>     sh7372/mackerel),
> but it's difficult to assess from the code whether the bug is really
> triggered on these platforms.
>
> Grygorii Strashko's "[PATCH v1 2/4] ARM: keystone: pm: switch to use
> generic pm domains" is not affected, as pm_clk_add_clk() is only called
> for existing clocks.
>
> If it crashes on marzen or mackerel, I think this fix needs to be
> applied to stable, too. I don't have access to marzen or mackerel boards,
> though.
>
> How to test:
>   - Build a kernel with CONFIG_PM_SLEEP/CONFIG_SUSPEND enabled, but
>     CONFIG_PM_RUNTIME disabled,
>   - echo 0 > /sys/module/printk/parameters/console_suspend,
>   - echo mem > /sys/power/state,
>   - wake up using e.g. gpio-keys or serial console activity.
> ---
>  drivers/base/power/clock_ops.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
> index b99e6c06ee678ecb..78369305e0698109 100644
> --- a/drivers/base/power/clock_ops.c
> +++ b/drivers/base/power/clock_ops.c
> @@ -368,8 +368,13 @@ int pm_clk_suspend(struct device *dev)
>
>         spin_lock_irqsave(&psd->lock, flags);
>
> -       list_for_each_entry_reverse(ce, &psd->clock_list, node)
> -               clk_disable(ce->clk);
> +       list_for_each_entry_reverse(ce, &psd->clock_list, node) {
> +               if (ce->status < PCE_STATUS_ERROR) {
> +                       if (ce->status == PCE_STATUS_ENABLED)
> +                               clk_disable(ce->clk);
> +                       ce->status = PCE_STATUS_ACQUIRED;
> +               }
> +       }
>
>         spin_unlock_irqrestore(&psd->lock, flags);
>
> @@ -385,6 +390,7 @@ int pm_clk_resume(struct device *dev)
>         struct pm_subsys_data *psd = dev_to_psd(dev);
>         struct pm_clock_entry *ce;
>         unsigned long flags;
> +       int ret;
>
>         dev_dbg(dev, "%s()\n", __func__);
>
> @@ -394,8 +400,13 @@ int pm_clk_resume(struct device *dev)
>
>         spin_lock_irqsave(&psd->lock, flags);
>
> -       list_for_each_entry(ce, &psd->clock_list, node)
> -               __pm_clk_enable(dev, ce->clk);
> +       list_for_each_entry(ce, &psd->clock_list, node) {
> +               if (ce->status < PCE_STATUS_ERROR) {
> +                       ret = __pm_clk_enable(dev, ce->clk);
> +                       if (!ret)
> +                               ce->status = PCE_STATUS_ENABLED;
> +               }
> +       }
>
>         spin_unlock_irqrestore(&psd->lock, flags);
>
> --
> 1.9.1

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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