lkml.org 
[lkml]   [2006]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
Date
From
SubjectRe: [PATCH] simplify update_times (avoid jiffies/jiffies_64 aliasing problem)
> b) On 64-bit machines jiffies and jiffies_64 always have the same
> address (don't they?) Is the compiler really going to move a read of an
> absolute address ahead of a modification of the same address?
>
> <looks>
>
> The address of jiffies isn't known until link time, so yup, the risk
> is there.

Yes maybe it would be better to just use #define there.
jiffies_64 always was a bit too clever.

>
> c) jiffies is declared volatile. In practice, if I know my gcc, it's
> just not going to play these reordering games with a volatile.
>
> If that's true, and if some standard (presumably c99) says that it
> must be true then I don't think we need the patch.

The standards definition of volatile is unfortunately quite vague,
so at least from this side you cannot rely on much.

Also I assume Atsushi-san did the patch because he saw a real problem?

-Andi

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-03-04 12:22    [W:0.104 / U:0.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site