Messages in this thread | | | Date | Sat, 24 May 2003 07:43:12 -0700 (PDT) | From | Davide Libenzi <> | Subject | RE: [Linux-ia64] Re: web page on O(1) scheduler |
| |
On Fri, 23 May 2003, Davide Libenzi wrote:
> You need a write memory barrier even on the unlock. Consider this : > > spinlock = 1; > ... > protected_resource = NEWVAL; > spinlock = 0; > > ( where spinlock = 0/1 strip down, but do not lose the concept, the lock > operation ). If a CPU reorder those writes, another CPU might see the lock > drop before the protected resource assignment. And this is usually bad > for obvious reasons.
David made me notice about a brain misfire here. You need protection even for loads crossing the unlock. For the same obvious reasons :) Yes, a realease barrier will be sufficent for ia64, while you'll need an mfence on P4.
- Davide
- 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/
| |