[PATCH] Clean up sys_shutdown

[PATCH] Clean up sys_shutdown

[Andi Kleen]

Clean up sys_shutdown exit path

Impact: cleanup, fix

Clean up sys_shutdown exit path. Factor out common code. Return
correct error code instead of always 0 on failure.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 kernel/sys.c |   24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

Index: linux/kernel/sys.c
===================================================================
--- linux.orig/kernel/sys.c	2009-04-07 16:09:58.000000000 +0200
+++ linux/kernel/sys.c	2009-04-07 16:43:17.000000000 +0200
@@ -360,6 +360,7 @@
 		void __user *, arg)
 {
 	char buffer[256];
+	int ret = 0;
 
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT))
@@ -397,7 +398,7 @@
 		kernel_halt();
 		unlock_kernel();
 		do_exit(0);
-		break;
+		panic("cannot halt");
 
 	case LINUX_REBOOT_CMD_POWER_OFF:
 		kernel_power_off();
@@ -417,29 +418,22 @@
 
 #ifdef CONFIG_KEXEC
 	case LINUX_REBOOT_CMD_KEXEC:
-		{
-			int ret;
-			ret = kernel_kexec();
-			unlock_kernel();
-			return ret;
-		}
+		ret = kernel_kexec();
+		break;
 #endif
 
 #ifdef CONFIG_HIBERNATION
 	case LINUX_REBOOT_CMD_SW_SUSPEND:
-		{
-			int ret = hibernate();
-			unlock_kernel();
-			return ret;
-		}
+		ret = hibernate();
+		break;
 #endif
 
 	default:
-		unlock_kernel();
-		return -EINVAL;
+		ret = -EINVAL;
+		break;
 	}
 	unlock_kernel();
-	return 0;
+	return ret;
 }
 
 static void deferred_cad(struct work_struct *dummy)

Re: [PATCH] Clean up sys_shutdown

[Andrew Morton]

On Wed, 8 Apr 2009 00:36:26 +0200 Andi Kleen <andi@firstfloor.org> wrote:

> Clean up sys_shutdown exit path
> 
> Impact: cleanup, fix
> 
> Clean up sys_shutdown exit path. Factor out common code.

OK.

> Return
> correct error code instead of always 0 on failure.

oh goody, that makes the patch a bugfix.

> --- linux.orig/kernel/sys.c	2009-04-07 16:09:58.000000000 +0200
> +++ linux/kernel/sys.c	2009-04-07 16:43:17.000000000 +0200
> @@ -360,6 +360,7 @@
>  		void __user *, arg)
>  {
>  	char buffer[256];
> +	int ret = 0;
>  
>  	/* We only trust the superuser with rebooting the system. */
>  	if (!capable(CAP_SYS_BOOT))
> @@ -397,7 +398,7 @@
>  		kernel_halt();
>  		unlock_kernel();
>  		do_exit(0);
> -		break;
> +		panic("cannot halt");
>  
>  	case LINUX_REBOOT_CMD_POWER_OFF:
>  		kernel_power_off();
> @@ -417,29 +418,22 @@
>  
>  #ifdef CONFIG_KEXEC
>  	case LINUX_REBOOT_CMD_KEXEC:
> -		{
> -			int ret;
> -			ret = kernel_kexec();
> -			unlock_kernel();
> -			return ret;
> -		}
> +		ret = kernel_kexec();
> +		break;
>  #endif
>  
>  #ifdef CONFIG_HIBERNATION
>  	case LINUX_REBOOT_CMD_SW_SUSPEND:
> -		{
> -			int ret = hibernate();
> -			unlock_kernel();
> -			return ret;
> -		}
> +		ret = hibernate();
> +		break;
>  #endif
>  
>  	default:
> -		unlock_kernel();
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		break;
>  	}
>  	unlock_kernel();
> -	return 0;
> +	return ret;
>  }

I wonder why this code uses lock_kernel().

Re: [PATCH] Clean up sys_shutdown

[Andi Kleen]

On Thu, Apr 09, 2009 at 10:14:16PM -0700, Andrew Morton wrote:
> I wonder why this code uses lock_kernel().

I suspect because there's no other lock and parallel shutdowns
would be bad, but I wouldn't be surprised if there
aren't some caller without.

We could just convert it to a new global mutex or something.
I think it would be safe on x86, but I'm not sure about
all the other architectures.

Actually a simple flag would be enough that returns when
one is already in progress (that wouldn't work if parallel ones
fail, but that's presumably unlikely)

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.