Messages in this thread | | | Date | Mon, 11 Jan 1999 11:23:32 +0000 | From | Jamie Lokier <> | Subject | Re: tutorial question: where mb() is needed? |
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On Sat, Jan 09, 1999 at 06:25:32AM +0000, Linus Torvalds wrote: > No. The spinlocks themselves contain the required SMP memory > synchronization points internally: otherwise they wouldn't be very > useful as locking primitives. For example, on intel any locked memory > reference (and the spinlocks do them) will act as a memory barrier, and > that's why you don't see any extra code in asm-i386/spinlocks.h - on > other architectures the spinlocks do other things to get the same goal.
Linus,
While the asm does force a processor-level barrier, the asm constraints don't force GCC to keep memory references in the right order around the barrier. I'm not sure if such a constraint is generally required. Can you comment on this?
-- Jamie
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