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From: "Richard B. Johnson"   To: Linux kernel   Subject: SMP spin-locks Date: Thu, 14 Jun 2001 13:26:05 -0400 (EDT) [thread overview] Message-ID:   (raw) I __finally__ got back on "the list". They finally fixed the company firewall! During my absence, I had the chance to look at some SMP code because of a performance problem (a few microseconds out of spec on a 130 MHz embedded system) and I have a question about the current spin-locks. Spin-locks now transfer control to the .text.lock segment. This is a separate segment that can be at an offset that is far away from the currently executing code. That may cause the cache to be reloaded. Further, each spin-lock invocation generates separate code within that segment. Question 1: Why? Question 2: What is the purpose of the code sequence, "repz nop" generated by the spin-lock code? Is this a processor BUG work-around? `as` doesn't "like" this sequence and, Intel doesn't seem to document it. Cheers, Dick Johnson Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips). "Memory is like gasoline. You use it up when you are running. Of course you get it all back when you reboot..."; Actual explanation obtained from the Micro$oft help desk.
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