Re: [PATCH] fix do_xor_speed 64-bit devision issue on 32-bits arch

[Boaz Harrosh <bharrosh@panasas.com>]

On 12/25/2011 07:31 AM, Benny Halevy wrote:
> On 2011-12-23 15:25, Jim Rees wrote:
>> fanchaoting wrote:
>>
>>   Benny Halevy 写道:
>>   > I am trying to build a pnfs client on a 32 bit system  and the
>>   > pnfs-latest  kernel fails to compile. I get the following error
>>   > 
>>   >  >  Building modules, stage 2.
>>   >  >  TEST    posttest
>>   >  > MODPOST 2046 modules
>>   >  >ERROR: "__udivdi3" [crypto/xor.ko] undefined!
>>   >  >make[1]: *** [__modpost] Error 1
>>   >  >make: *** [modules] Error 2
>>   >  >make: *** Waiting for unfinished jobs....
>>   >  >Succeed: decoded and checked 1244492 instructions
>>   > 
>>   > Reported-by: Rita Sequeira <rita.prajval@gmail.com>
>>   > Signed-off-by: Benny Halevy <bhalevy@tonian.com>
>>   > ---
>>   > 
>>   > untested patch yet...
>>   > 
>>   >  crypto/xor.c |    3 ++-
>>   >  1 files changed, 2 insertions(+), 1 deletions(-)
>>   > 
>>   > diff --git a/crypto/xor.c b/crypto/xor.c
>>   > index 65433f5..2151ded 100644
>>   > --- a/crypto/xor.c
>>   > +++ b/crypto/xor.c
>>   > @@ -95,7 +95,8 @@
>>   >  
>>   >  	ns_end -= ns_begin;
>>   >  	if (ns_end > 0)
>>   > -		speed = BENCH_SIZE / 1024 * count * NSEC_PER_SEC / ns_end;
>>   > +		speed = BENCH_SIZE / 1024 * count *
>>   > +				(unsigned)(NSEC_PER_SEC / ns_end);
>>   >  	else
>>   >  		speed = 17;
>>   >  	tmpl->speed = speed;
>>   
>>   Hi,I also meet this problem ,but when  i use you patch ,i can't solve this
>>   problem.
>>
>> Maybe something like this?
>>
>> speed = do_div(BENCH_SIZE, 1024) * count * do_div(NSEC_PER_SEC, ns_end);
>>
>> This might not be exactly right because it changes the operator precedence,
>> but it should eliminate the calls to __udivdi3.
> 
> Hmm, you mean execution order? (which you do not)
> C (and fortunately gcc too :) treats multiplication and division with the
> same priority and executes them from left to right...
> 
> Boaz, please ack...
> 

Hi

Please trash this patch for now. I will carry it out of tree for my use.
(Looks I'm the only one who's using UML and the XOR engine)

By next Connectathon I'll have a better patch sent to the right
people.

Thanks for your efforts, and sorry for the grief it caused.
Boaz

> Benny
> 
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