Re: panic with tg_shares_up again?

[Yinghai Lu <yinghai@kernel.org>]

Ken Chen wrote:
> On Tue, Dec 23, 2008 at 3:46 PM, Ken Chen <kenchen@google.com> wrote:
>> And from my local build of linux-tip with the patch, I have the
>> following assembly:
>>     1  ffffffff8023b74f:  48 8b 88 a8 00 00 00    mov    0xa8(%rax),%rcx
>>     2  ffffffff8023b756:  48 c7 45 d0 00 00 00    movq   $0x0,-0x30(%rbp)
>>     3  ffffffff8023b75d:  00
>>     4  ffffffff8023b75e:  48 85 c9                test   %rcx,%rcx
>>     5  ffffffff8023b761:  0f 95 c0                setne  %al
>>     6  ffffffff8023b764:  84 45 af                test   %al,-0x51(%rbp)
>>     7  ffffffff8023b767:  74 15                   je     ffffffff8023b77e
>>     8  ffffffff8023b769:  48 8b 45 b8             mov    -0x48(%rbp),%rax
>>     9  ffffffff8023b76d:  31 d2                   xor    %edx,%edx
>>    10  ffffffff8023b76f:  48 0f af c1             imul   %rcx,%rax
>>    11  ffffffff8023b773:  48 f7 75 b0             divq   -0x50(%rbp)
>>
>> line 6 is the compare against sd_rq_weight, but it was only to one
>> byte instead of the entire unsigned long.
>>
>> /me scratching my head ....
> 
> After a couple of hours joggling with type cast and different order in
> which these two variables are checked, the compiler I'm using seems to
> insist only check one byte out of sd_rq_weight.  I give up for the day
> and removed the 'static' function declaration of
> update_group_shares_cpu().  Without the 'static', the assembly looks
> alright to me.
> 
> I will ask compiler expert to see what's wrong with this code.  For
> now, the following add on patch seems generate correct x86 assembly
> code.

maybe my compiler has some problem too?  just upgrade to opensuse 11.1 last week.

yhlu@linux-mstp:~/xx/xx/kernel/tip/linux-2.6> gcc --version
gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.