Re: [Xen-devel] [PATCH RFC 04/25] Replace "/" operand with div64

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 7 Dec 2011, Zhang, Xiantao wrote:
> Hi, Stefano 
> Great work from you guys!  One quick comment:  Just found the below logic's 
> change maybe wrong and probably  break current things. 
> Original logic is  A+B -(C%D), but it is changed to  (A+B-C)%D,  so if it is 
> not an intended fix, it should be an issue. 
> Thanks!
> Xiantao  

True! Thanks for spotting this!

> >diff --git a/xen/common/timer.c b/xen/common/timer.c index 0547ea3..043250e 
> >100644
> >--- a/xen/common/timer.c
> >+++ b/xen/common/timer.c
> >@@ -23,6 +23,7 @@
> >#include <xen/symbols.h>
> >#include <asm/system.h>
> >#include <asm/desc.h>
> >+#include <asm/div64.h>
> > #include <asm/atomic.h>
> > 
> > /* We program the time hardware this far behind the closest deadline. */ @@ 
> > -503,16 +504,18 @@ static void timer_softirq_action(void)
> > 
> > s_time_t align_timer(s_time_t firsttick, uint64_t period)  {
> >+    uint64_t n;
>  >    if ( !period )
>  >        return firsttick;
>  
> >-    return firsttick + (period - 1) - ((firsttick - 1) % period);
> >+    n = firsttick + (period - 1) - (firsttick - 1);
> >+    return do_div(n, period);
> > }
>  
> 

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