Messages in this thread | | | Date | 4 Mar 2006 12:20:10 +0100 | Date | Sat, 4 Mar 2006 12:20:10 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH] simplify update_times (avoid jiffies/jiffies_64 aliasing problem) |
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> 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
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