linux-kernel - Re: Improve hackbench

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Message-ID: <20080104125420.GA20981@elte.hu>
Date:	Fri, 4 Jan 2008 13:54:20 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Török Edwin <edwintorok@...il.com>
Cc:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: Improve hackbench


* Török Edwin <edwintorok@...il.com> wrote:

> On x86-64 there's a bug [*], that causes hackbench to segfault when
> compiled with optimizations:
> in reap_worker():
>     int status;
> ...
>     pthread_join(id, (void **)(void *)&status);
> 
> That is not correct, sizeof(void*) > sizeof(int) on x86-64.
> Something gets overwritten on the stack, I tried with gcc
> -fstack-protector, but it doesn't detect it !?
> After applying the patch, it no longer segfaults.
> 
> This patch fixes it:
> --- hackbench.c 2008-01-04 10:08:26.000000000 +0200
> +++ ../hackbench.c      2008-01-04 13:45:22.000000000 +0200
> @@ -241,8 +241,10 @@
>                 wait(&status);
>                 if (!WIFEXITED(status))
>                         exit(1);
> -       } else
> -               pthread_join(id, (void **)(void *)&status);
> +       } else {
> +               void* status;
> +               pthread_join(id, (void **)&status);
> +       }
>  }

thanks, applied & updated the file.

	Ingo
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