![]() | |||||||||||
Messages in this thread |
> In Intel machines ALL memory operations are atomic. What > the means is that if I make code that does: > > addl %eax,(memory) > > ... what's in memory will always be the sum of what it was > before and the value in the EAX register. Except on SMP. > A long time ago, somebody invented the 'lock' instruction > for Intel machines. It turns out that the first ones locked > the whole bus during an operation. Eventually somebody looked > at that, and by the time the '486 came out, they no longer > locked the whole bus. Then somebody else said; "WTF... > Why do we even need this stuff". It was a throw-back to > early primitive machines where there were only load and > store operations in memory. All arithmetic had to be done > in registers. Now, there are only a couple instructions you > can use the lock prefix with, or you get an invalid opcode > trap, and they are really no-ops because the instruction > itself is atomic. Not on SMP. On SMP, lock prefix *is needed*. If you think I'm wrong, point me to the relevant docs. -- vda - 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: 2005-03-22 14:03 [from the cache] ©2003-2008 | |||||||||||