linux-kernel - Re: [PATCH v2] scsi: ufs: core: Ensure clk_gating.lock is used only after initialization

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Message-ID: <CAMuHMdVHMH8=i3v=qYGhR5t+mbz07TyS7b=6OnnxmHox58c7Eg@mail.gmail.com>
Date: Fri, 24 Jan 2025 13:03:04 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Avri Altman <avri.altman@....com>
Cc: "Martin K . Petersen" <martin.petersen@...cle.com>, linux-scsi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Manivannan Sadhasivam <manisadhasivam.linux@...il.com>, Bart Van Assche <bvanassche@....org>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH v2] scsi: ufs: core: Ensure clk_gating.lock is used only
 after initialization

Hi Avri,

On Fri, Jan 24, 2025 at 8:36 AM Avri Altman <avri.altman@....com> wrote:
> This commit addresses a lockdep warning triggered by the use of the
> clk_gating.lock before it is properly initialized. The warning is as
> follows:
>
> [    4.388838] INFO: trying to register non-static key.
> [    4.395673] The code is fine but needs lockdep annotation, or maybe
> [    4.402118] you didn't initialize this object before use?
> [    4.407673] turning off the locking correctness validator.
> [    4.413334] CPU: 5 UID: 0 PID: 58 Comm: kworker/u32:1 Not tainted 6.12-rc1 #185
> [    4.413343] Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
> [    4.413362] Call trace:
> [    4.413364]  show_stack+0x18/0x24 (C)
> [    4.413374]  dump_stack_lvl+0x90/0xd0
> [    4.413384]  dump_stack+0x18/0x24
> [    4.413392]  register_lock_class+0x498/0x4a8
> [    4.413400]  __lock_acquire+0xb4/0x1b90
> [    4.413406]  lock_acquire+0x114/0x310
> [    4.413413]  _raw_spin_lock_irqsave+0x60/0x88
> [    4.413423]  ufshcd_setup_clocks+0x2c0/0x490
> [    4.413433]  ufshcd_init+0x198/0x10ec
> [    4.413437]  ufshcd_pltfrm_init+0x600/0x7c0
> [    4.413444]  ufs_qcom_probe+0x20/0x58
> [    4.413449]  platform_probe+0x68/0xd8
> [    4.413459]  really_probe+0xbc/0x268
> [    4.413466]  __driver_probe_device+0x78/0x12c
> [    4.413473]  driver_probe_device+0x40/0x11c
> [    4.413481]  __device_attach_driver+0xb8/0xf8
> [    4.413489]  bus_for_each_drv+0x84/0xe4
> [    4.413495]  __device_attach+0xfc/0x18c
> [    4.413502]  device_initial_probe+0x14/0x20
> [    4.413510]  bus_probe_device+0xb0/0xb4
> [    4.413517]  deferred_probe_work_func+0x8c/0xc8
> [    4.413524]  process_scheduled_works+0x250/0x658
> [    4.413534]  worker_thread+0x15c/0x2c8
> [    4.413542]  kthread+0x134/0x200
> [    4.413550]  ret_from_fork+0x10/0x20
>
> To fix this issue, ensure that the spinlock is only used after it
> has been properly initialized before using it in `ufshcd_setup_clocks`.
>
> Fixes: 209f4e43b806 ("scsi: ufs: core: Introduce a new clock_gating lock")
> Reported-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Avri Altman <avri.altman@....com>

> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c

> @@ -10412,6 +10410,13 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>         hba->irq = irq;
>         hba->vps = &ufs_hba_vps;
>
> +       /*
> +        * Initialize clk_gating.lock early since it is being used in
> +        * ufshcd_setup_clocks()
> +        */
> +       if (ufshcd_is_clkgating_allowed(hba))

This checks if the UFSHCD_CAP_CLK_GATING flag is set, which is only
done in a subset of the host drivers:

drivers/ufs/host/ufs-exynos.c:  hba->caps |= UFSHCD_CAP_CLK_GATING |
UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
drivers/ufs/host/ufs-mediatek.c:        hba->caps |= UFSHCD_CAP_CLK_GATING;
drivers/ufs/host/ufs-qcom.c:    hba->caps |= UFSHCD_CAP_CLK_GATING |
UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
drivers/ufs/host/ufs-sprd.c:    hba->caps |= UFSHCD_CAP_CLK_GATING |

> +               spin_lock_init(&hba->clk_gating.lock);

Hence the spinlock is not uninitialized on all other host drivers.

> +
>         err = ufshcd_hba_init(hba);
>         if (err)
>                 goto out_error;

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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