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Date:	Tue, 23 Jun 2009 15:44:29 -0700
From:	"Kevin D. Kissell" <kevink@paralogos.com>
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To:	Kaz Kylheku <KKylheku@zeugmasystems.com>
CC:	linux-mips@linux-mips.org
Subject: Re: Silly 100% CPU behavior on a SIG_IGN-ored SIGBUS.
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Kaz Kylheku wrote:
> Hi all,
>
> On kernel 2.6.26, glibc 2.5 (n32), SiByte SB-1 core, the following
> program goes into 100% CPU, chewing up about 80% kernel time and
> 20% user.
>
> #include <stdio.h>
> #include <signal.h>
>
> int main(void)
> {
>   int *deadbeef = (int *) 0xdeadbeef;
>   signal(SIGBUS, SIG_IGN);
>   printf("*deadbeef == %d\n", *deadbeef);
>   return 0;
> }
>
> If any fatal exception is ignored, the program should be killed
> if that exception happens. 100% CPU is not a useful response.
>   
It's not a useful program, so what did you expect?   One might argue 
that it would be more useful or correct to have the kernel advance the 
PC to not endlessly repeat the doomed load, but ignoring SIG_IGN and 
silently killing the thread violates the signal API as I've always 
understood it.

          Regards,

          Kevin K.