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Date: Fri, 30 May 2008 21:38:23 -0700 From: Ulrich Drepper <drepper@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> CC: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, mtk.manpages@...il.com Subject: Re: [PATCH 0/3] 64-bit futexes: Intro -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Linus Torvalds wrote: > Is it possible? I dunno. Once again not without limitations which are too low. The main problem is that there is far more information needed on the reader side. There are two counters and a number of bits for state information. Which means the counters can be at most 14 bits in size. A counter this low also means I cannot unconditionally increment them (since there can be more than 2^14 threads sharing one page). This means you get in the cache line race I described in the last mail. You first have to load a word and then perform a the write operation while at the same time other threads competing with you for the same cache line. > I personally suspect it is. I also suspect you > didn't even try. I have to disappoint you. I thought of that and had to reject it. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkhA1j8ACgkQ2ijCOnn/RHTUXQCgnkUy6PNSuUI4O6BD4abxqqKr PzMAn2qcvrXGM4qrhOytk1Yie0BsMeVa =zvxZ -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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