linux-kernel - RE: sched: about vruntime overflow

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Date:	Tue, 7 Jul 2015 09:18:36 +0000
From:	"Gaohaifeng (A)" <gaohaifeng.gao@...wei.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stephan.baerwolf@...ilmenau.de" <stephan.baerwolf@...ilmenau.de>,
	"Huangjian (J)" <huangjian.huangjian@...wei.com>
Subject: RE: sched:  about vruntime overflow

Much Thanks!


On Tue, Jul 07, 2015 at 08:05:50AM +0000, Gaohaifeng (A) wrote:
> int main()
> {
>         unsigned char a,b;
>         a=251;
>         b=254;
>         b +=5;  // b will overflow
>         printf("a=%u \n",a);
>         printf("b=%u \n",b);
>         printf("(a-b<0)=%d\n",(a-b)<0);

If you look at entity_before() you'll notice that the correct statement would be:

	printf("(a-b<0)=%d\n",(signed char)(a-b)<0);

>         printf("(a-b<0)=%d\n",((unsigned char)(a-250)-(unsigned char)(b-250)<0));
>         return 0;
> }

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