[PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[Rakib Mullick]

Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, 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. Both acpi_gbl_hardware_lock and acpi_gbl_gpe_lock are at same lock-class and which might cause lock recursion deadlock. 

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.

 Changes since v1 (https://lkml.org/lkml/2011/11/3/89):
	- Update changelog and rename goto label, courtesy Srivatsa S. Bhat.

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
index 55accb7..cc70f3f 100644
--- a/drivers/acpi/acpica/hwregs.c
+++ b/drivers/acpi/acpica/hwregs.c
@@ -269,16 +269,17 @@ acpi_status acpi_hw_clear_acpi_status(void)
 
 	status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
 					ACPI_BITMASK_ALL_FIXED_STATUS);
-	if (ACPI_FAILURE(status)) {
-		goto unlock_and_exit;
-	}
+
+	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
+
+	if (ACPI_FAILURE(status))
+		goto exit;
 
 	/* Clear the GPE Bits in all GPE registers in all GPE blocks */
 
 	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);
+exit:
 	return_ACPI_STATUS(status);
 }
 

Re: [PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[Srivatsa S. Bhat]

On 11/06/2011 08:48 PM, Rakib Mullick wrote:
> Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, 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. Both acpi_gbl_hardware_lock and acpi_gbl_gpe_lock are at same lock-class and which might cause lock recursion deadlock. 
> 
> 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.
> 
>  Changes since v1 (https://lkml.org/lkml/2011/11/3/89):
> 	- Update changelog and rename goto label, courtesy Srivatsa S. Bhat.
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
> Cc: Lin Ming <ming.m.lin@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
> 

It would be a good idea to also give the lockdep warning in the changelog
(though you triggered it in a modified kernel), since that would make
it very clear as to what problem your patch is trying to solve.
[And please line-wrap your changelog to 80 characters at most, per line].

Code-wise, the patch looks good to me. So,
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Thanks,
Srivatsa S. Bhat

> diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
> index 55accb7..cc70f3f 100644
> --- a/drivers/acpi/acpica/hwregs.c
> +++ b/drivers/acpi/acpica/hwregs.c
> @@ -269,16 +269,17 @@ acpi_status acpi_hw_clear_acpi_status(void)
> 
>  	status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
>  					ACPI_BITMASK_ALL_FIXED_STATUS);
> -	if (ACPI_FAILURE(status)) {
> -		goto unlock_and_exit;
> -	}
> +
> +	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
> +
> +	if (ACPI_FAILURE(status))
> +		goto exit;
> 
>  	/* Clear the GPE Bits in all GPE registers in all GPE blocks */
> 
>  	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);
> +exit:
>  	return_ACPI_STATUS(status);
>  }
> 
> 
> 

Re: [PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[Rafael J. Wysocki]

On Sunday, November 06, 2011, Rakib Mullick wrote:
> Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, 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. Both acpi_gbl_hardware_lock and acpi_gbl_gpe_lock are at same lock-class and which might cause lock recursion deadlock. 
> 
> 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.
> 
>  Changes since v1 (https://lkml.org/lkml/2011/11/3/89):
> 	- Update changelog and rename goto label, courtesy Srivatsa S. Bhat.
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
> Cc: Lin Ming <ming.m.lin@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Acked-by: Rafael J. Wysocki <rjw@sisk.pl>

> ---
> 
> diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
> index 55accb7..cc70f3f 100644
> --- a/drivers/acpi/acpica/hwregs.c
> +++ b/drivers/acpi/acpica/hwregs.c
> @@ -269,16 +269,17 @@ acpi_status acpi_hw_clear_acpi_status(void)
>  
>  	status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
>  					ACPI_BITMASK_ALL_FIXED_STATUS);
> -	if (ACPI_FAILURE(status)) {
> -		goto unlock_and_exit;
> -	}
> +
> +	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
> +
> +	if (ACPI_FAILURE(status))
> +		goto exit;
>  
>  	/* Clear the GPE Bits in all GPE registers in all GPE blocks */
>  
>  	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);
> +exit:
>  	return_ACPI_STATUS(status);
>  }
>  
> 
> 
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Re: [PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[Len Brown]

applied.

thanks,
Len Brown, Intel Open Source Technology Center

Re: [PATCH -v2] acpi: Fix possible recursive locking in hwregs.c

[Rakib Mullick]

On Mon, Nov 7, 2011 at 1:46 AM, Srivatsa S. Bhat
<srivatsa.bhat@linux.vnet.ibm.com> wrote:
> On 11/06/2011 08:48 PM, Rakib Mullick wrote:
>
> It would be a good idea to also give the lockdep warning in the changelog
> (though you triggered it in a modified kernel), since that would make
> it very clear as to what problem your patch is trying to solve.

At the time of this reply, it's been taken. So, I'll keep it on mind
for next time.

> [And please line-wrap your changelog to 80 characters at most, per line].
>
Gmail's email editor automatically puts break on a line, that's why I
didn't put any line break on changelog. While I was reading my patch
on lkml.org, I've noticed that it creates a big one line changelog,
which is a bit weird. So, will keep it under 80 line from next time.

> Code-wise, the patch looks good to me. So,
> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>

Thanks,
Rakib