Messages in this thread | | | Date | Tue, 10 Apr 2001 22:05:51 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] i386 rw_semaphores fix |
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On Tue, Apr 10, 2001 at 12:42:07PM -0700, Linus Torvalds wrote: > > > On Tue, 10 Apr 2001, David Howells wrote: > > > > Here's a patch that fixes RW semaphores on the i386 architecture. It is very > > simple in the way it works. > > XADD only works on Pentium+.
My Intel manual says it 486+:
`` XADD-Exchange and Add [...] Intel Architecture Compatibility Intel Architecture processors earlier than the Intel486TM processor do not recognize this instruc- tion. If this instruction is used, you should provide an equivalent code sequence that runs on earlier processors. ''
I guess 386 could live with an exception handler that emulates it.
(BTW an generic exception handler for CMPXCHG would also be very useful for glibc -- currently it has special checking code for 386 in its mutexes) The 386 are so slow that nobody would probably notice a bit more slowness by a few exceptions.
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