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On Sat, Jan 12, 2002 at 02:48:53AM -0800, Adam J. Richter wrote: > H. Peter Anvin wrote, in response to Andi Kleen: > >You don't need CMPXCHG8B to do efficient inline mutexes. In fact, the > >pthreads code for i386 uses the same mutexes the kernel does (LOCK INC > >based, I believe), complete with section hacking to make them > >efficiently inlinable -- and then they're put inside a function call. > [...] > > Your comment prompted me to look at > linux-2.5.2-pre11/include/asm-i386/spinlock.h, and I now believe that > the "lock; decb" that it uses for grabbing spinlocks will return an > incorrect success if 255 or more processors are waiting on the same > spinlock. I don't know if anybody has ever built a shared memory x86 > multiprocessor with 257 (not a typo) or more CPU's, but it's possible > to imagine. It's also possible to imagine this scenario happening > with even just one processor and a preemtable kernel. I believe that > the current preemtable kernel patch limits the number of preempted > processes to something like four or six, but that's just a temporary > limitation of the current version. AFAIK, there's more code than this that won't work with >255 processors... It's not like each and every person on this list has such a beast to test with (and probably most never will even if they do exist, or come to existance...) Regards: David Weinehall _ _ // David Weinehall <tao@acc.umu.se> /> Northern lights wander \\ // Maintainer of the v2.0 kernel // Dance across the winter sky // \> http://www.acc.umu.se/~tao/ </ Full colour fire </ - 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/ | |||||||||
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