linux-kernel - Re: [PATCH] acpi: Fix possible recursive locking in hwregs.c

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Message-ID: <CAF1ivSbZf5zgJphyaLeUZfSgz-oPvAY0bG6V2OMeWPS60nsxxQ@mail.gmail.com>
Date:	Thu, 22 Sep 2011 08:59:57 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-acpi@...r.kernel.org, Bob Moore <robert.moore@...el.com>
Subject: Re: [PATCH] acpi: Fix possible recursive locking in hwregs.c

On Thu, Sep 22, 2011 at 2:09 AM, Rakib Mullick <rakib.mullick@...il.com> wrote:
> Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status,
> acpi_os_release_lock holds the lock acpi_gbl_hardware_lock before calling acpi_hw_register_write(), then
> without releasing acpi_gbl_hardware_lock, this function calls acpi_ev_walk_gpe_list, which also tries to
> hold acpi_gbl_hardware_lock and thus causes possible recursive lock.

No, acpi_ev_walk_gpe_list holds acpi_gbl_gpe_lock.

Lin Ming

>
> Following patch fixes this scenario by just releasing acpi_gbl_hardware_lock before calling acpi_ev_walk_gpe_list.
>
> [This patch was created against 3.0-rc3. Since kernel.org is down, I don't have the updated tree. So, before applying
> it might require some adjustment.]
>
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
> ---
>
> diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
> index 55accb7..e3110ac 100644
> --- a/drivers/acpi/acpica/hwregs.c
> +++ b/drivers/acpi/acpica/hwregs.c
> @@ -269,6 +269,9 @@ acpi_status acpi_hw_clear_acpi_status(void)
>
>        status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
>                                        ACPI_BITMASK_ALL_FIXED_STATUS);
> +
> +       acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
> +
>        if (ACPI_FAILURE(status)) {
>                goto unlock_and_exit;
>        }
> @@ -278,7 +281,6 @@ acpi_status acpi_hw_clear_acpi_status(void)
>        status = acpi_ev_walk_gpe_list(acpi_hw_clear_gpe_block, NULL);
>
>       unlock_and_exit:
> -       acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
>        return_ACPI_STATUS(status);
>  }
>
>
>
> --
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