linux-kernel - Re: [PATCH -v1] acpi: Fix possible recursive locking in hwregs.c

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Date:	Thu, 03 Nov 2011 20:02:50 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Brown, Len" <len.brown@...el.com>,
	"Moore, Robert" <robert.moore@...el.com>
Subject: Re: [PATCH -v1] acpi: Fix possible recursive locking in hwregs.c

On Thu, 2011-11-03 at 18:48 +0800, Rakib Mullick wrote:
> Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, 

As I replied at https://lkml.org/lkml/2011/9/22/6, I still don't think
there is a recursive lock.

Or do you have a real test case to trigger the recursive lock you
mentioned?

Lin Ming

> acpi_os_acquire_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 tries to hold 
> acpi_gbl_gpe_lock and thus might causes possible recursive lock.
> 
> Following patch fixes this scenario by just releasing acpi_gbl_hardware_lock before calling acpi_ev_walk_gpe_list.
> 
>  Changes since v0(https://lkml.org/lkml/2011/9/21/355):
> 	- Fix changelog, thanks to Lin Ming.
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
> Cc: Lin Ming <ming.m.lin@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Len Brown <len.brown@...el.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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