[PATCH] powerpc: _exception: kill the obsolete code under is_global_init()

[PATCH] powerpc: _exception: kill the obsolete code under is_global_init()

[Oleg Nesterov]

The code under "if (is_global_init())" is bogus, and is_global_init()
itself is not right in mt case.

Contrary to what the comment says, nowadays force_sig_info() does kill
init even if the handler is SIG_DFL. Note that force_sig_info() clears
SIGNAL_UNKILLABLE exactly for this case.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 arch/powerpc/kernel/traps.c |   22 ----------------------
 1 file changed, 22 deletions(-)

--- TH/arch/powerpc/kernel/traps.c~PPC_EXCEPTION_DONT_CK_INIT	2009-11-10 01:03:23.000000000 +0100
+++ TH/arch/powerpc/kernel/traps.c	2009-11-10 01:06:41.000000000 +0100
@@ -198,28 +198,6 @@ void _exception(int signr, struct pt_reg
 	info.si_code = code;
 	info.si_addr = (void __user *) addr;
 	force_sig_info(signr, &info, current);
-
-	/*
-	 * Init gets no signals that it doesn't have a handler for.
-	 * That's all very well, but if it has caused a synchronous
-	 * exception and we ignore the resulting signal, it will just
-	 * generate the same exception over and over again and we get
-	 * nowhere.  Better to kill it and let the kernel panic.
-	 */
-	if (is_global_init(current)) {
-		__sighandler_t handler;
-
-		spin_lock_irq(&current->sighand->siglock);
-		handler = current->sighand->action[signr-1].sa.sa_handler;
-		spin_unlock_irq(&current->sighand->siglock);
-		if (handler == SIG_DFL) {
-			/* init has generated a synchronous exception
-			   and it doesn't have a handler for the signal */
-			printk(KERN_CRIT "init has generated signal %d "
-			       "but has no handler for it\n", signr);
-			do_exit(signr);
-		}
-	}
 }
 
 #ifdef CONFIG_PPC64

Re: [PATCH] powerpc: _exception: kill the obsolete code under is_global_init()

[Benjamin Herrenschmidt]

On Tue, 2009-11-10 at 01:25 +0100, Oleg Nesterov wrote:
> The code under "if (is_global_init())" is bogus, and is_global_init()
> itself is not right in mt case.
> 
> Contrary to what the comment says, nowadays force_sig_info() does kill
> init even if the handler is SIG_DFL. Note that force_sig_info() clears
> SIGNAL_UNKILLABLE exactly for this case.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---

Thanks. I'll take that one.

Cheers,
Ben.

>  arch/powerpc/kernel/traps.c |   22 ----------------------
>  1 file changed, 22 deletions(-)
> 
> --- TH/arch/powerpc/kernel/traps.c~PPC_EXCEPTION_DONT_CK_INIT	2009-11-10 01:03:23.000000000 +0100
> +++ TH/arch/powerpc/kernel/traps.c	2009-11-10 01:06:41.000000000 +0100
> @@ -198,28 +198,6 @@ void _exception(int signr, struct pt_reg
>  	info.si_code = code;
>  	info.si_addr = (void __user *) addr;
>  	force_sig_info(signr, &info, current);
> -
> -	/*
> -	 * Init gets no signals that it doesn't have a handler for.
> -	 * That's all very well, but if it has caused a synchronous
> -	 * exception and we ignore the resulting signal, it will just
> -	 * generate the same exception over and over again and we get
> -	 * nowhere.  Better to kill it and let the kernel panic.
> -	 */
> -	if (is_global_init(current)) {
> -		__sighandler_t handler;
> -
> -		spin_lock_irq(&current->sighand->siglock);
> -		handler = current->sighand->action[signr-1].sa.sa_handler;
> -		spin_unlock_irq(&current->sighand->siglock);
> -		if (handler == SIG_DFL) {
> -			/* init has generated a synchronous exception
> -			   and it doesn't have a handler for the signal */
> -			printk(KERN_CRIT "init has generated signal %d "
> -			       "but has no handler for it\n", signr);
> -			do_exit(signr);
> -		}
> -	}
>  }
>  
>  #ifdef CONFIG_PPC64