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Groups > comp.programming.threads > #2177
| From | "Chris M. Thomasson" <no@spam.invalid> |
|---|---|
| Newsgroups | comp.programming.threads, comp.programming, comp.arch |
| Subject | Re: About lockfree and waitfree... (2nd try) |
| Date | 2014-04-17 16:35 -0700 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <lipog6$raa$1@speranza.aioe.org> (permalink) |
| References | (3 earlier) <lihioq$ubs$1@speranza.aioe.org> <lihjlm$q0$1@speranza.aioe.org> <lihr02$g62$2@dont-email.me> <lijor8$a3k$1@speranza.aioe.org> <lijqjp$ri0$1@dont-email.me> |
Cross-posted to 3 groups.
> "Ivan Godard" wrote in message news:lijqjp$ri0$1@dont-email.me... > > On 4/15/2014 10:04 AM, Chris M. Thomasson wrote: > >> "Ivan Godard" wrote in message news:lihr02$g62$2@dont-email.me... On > >> 4/14/2014 2:23 PM, Chris M. Thomasson wrote: > >> >> "Chris M. Thomasson" wrote in message > >> >> news:lihioq$ubs$1@speranza.aioe.org... [...] correction: > > [...] > >> > The membar needs to be before the load of the eventcount because the > >> > mutations to the user state that we are signaling about needs to be > >> > visible to the consumers. > >> > > >> > I hate devious membar bugs! > >> > > >> > Grrr..... > > > >> Are the membars necessary at all if the machine is strict sequential > >> concurrency? > > > > If all of the atomics already have implied "memory_order_seq_cst" > > semantics, then you would _not_ need an explicit memory barrier > > because the #StoreLoad ordering is already built in. > > > > FWIW, I need #StoreLoad ordering here. This part of the algorithm > > requires that a store to location A has to be visible _before_ a load > > from location B. Acquire/release semantics is simply not strong > > enough here. This is one place where you need an explicit barrier > > on an x86. This could be MFENCE, or a dummy call to an atomic > > RMW... > I ask because the Mill is strict sequential concurrency, but we have > heard of cases in which that is insufficient for certain lock-free > algorithms, which are only correct with a global strict ordering (i.e. > global timestamps), but potentially fail with an arbitrary interleaving > of local strict ordering (i.e. sequential consistency). If you have a hard core setup where you execute the equivalent of an: MEMBAR #StoreLoad | #StoreStore| #LoadStore | #LoadLoad; SPARC instruction before and after each atomic operation, and the algorithm still fails, then I would look into errors in the actual algorithm logic itself. IMVHO, it is probably not keeping sync with the global timestamp. Or, there may be a problem in the monotonic timestamp generator, wrt overflow or something... This does not sound Kosher! > Frankly, this stuff makes my head hurt. I am can second that! :^)
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About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 19:54 -0700
Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-13 19:38 -0700
Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-13 19:47 -0700
Re: About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 22:56 -0700
Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-14 14:08 -0700
Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-14 14:23 -0700
Re: About lockfree and waitfree... Ivan Godard <ivan@ootbcomp.com> - 2014-04-14 16:27 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-14 16:29 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-15 10:04 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-15 10:34 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-17 16:35 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 17:04 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-18 09:54 +0100
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-18 02:31 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-18 11:56 +0100
Re: About lockfree and waitfree... (2nd try) rpw3@rpw3.org (Rob Warnock) - 2014-04-18 11:26 +0000
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-18 13:30 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:25 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:31 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-21 14:53 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 14:21 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 14:36 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-22 15:30 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-05-01 00:48 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-05-25 13:16 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:34 -0700
Re: About lockfree and waitfree... (2nd try) Robert Wessel <robertwessel2@yahoo.com> - 2014-04-21 16:42 -0500
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-21 15:02 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-22 09:05 +0100
Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-22 09:27 -0700
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-22 09:45 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-22 18:08 +0100
Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-23 12:08 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-23 20:32 +0100
Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-23 13:21 -0700
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-23 21:51 +0100
Re: About lockfree and waitfree... (2nd try) Chris Gray <cg@GraySage.COM> - 2014-04-24 10:53 -0600
Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-24 18:02 +0100
Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-25 13:39 -0700
Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 22:08 -0700
Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-17 21:15 -0400
Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-17 21:25 -0400
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 19:17 -0700
Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-18 00:46 -0400
Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 18:52 -0700
Re: About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 22:54 -0700
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