lkml.org 
[lkml]   [2015]   [May]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Compilers and RCU readers: Once more unto the breach!
On Wed, May 20, 2015 at 02:44:30PM +0100, Ramana Radhakrishnan wrote:
>
>
> On 20/05/15 14:37, David Howells wrote:
> >Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> >
> >>I was thinking of "y" as a simple variable, but if it is something more
> >>complex, then the compiler could do this, right?
> >>
> >> char *x;
> >>
> >> y;
> >> x = z;
> >
> >Yeah. I presume it has to maintain the ordering, though.
>
> The scheduler for e.g. is free to reorder if it can prove there is
> no dependence (or indeed side-effects for y) between insns produced
> for y and `x = z'.

So for example, if y is independent of z, the compiler can do the
following:

char *x;

x = z;
y;

But the dependency ordering is still maintained from z to x, so this
is not a problem.

Or am I missing something subtle here?

Thanx, Paul



\
 
 \ /
  Last update: 2015-05-20 16:21    [W:0.083 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site