Re: arm ldxr/stxr vs cas

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Sujet : Re: arm ldxr/stxr vs cas
De : already5chosen (at) *nospam* yahoo.com (Michael S)
Groupes : comp.arch
Date : 08. Sep 2024, 18:46:21
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <20240908204621.000062d1@yahoo.com>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14
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On Sun, 08 Sep 2024 16:10:41 GMT
scott@slp53.sl.home (Scott Lurndal) wrote:

"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:
On 9/7/2024 5:59 PM, MitchAlsup1 wrote: 
On Sat, 7 Sep 2024 23:16:35 +0000, Chris M. Thomasson wrote: 
 
Thus, it seems reasonable to fail a CAS when one cannot determine
if the memory location has been changed and changed back in the
mean time. 
>
I think Scott Lurndal mentioned something about CAS or something on
windows that will assert the bus lock after a lot of failures... 
 
On AMD processors (and likely intel), if a core cannot acquire
a cache line in a a finite time, the core will assert the bus lock
to ensure forward progress.
 
Nothing to do with the operating software;  purely a hardware thing.


I think, on AMD processors made in this century the only cases that
resort to physical bus lock are
A) atomic accesses that cross cache boundary
B) atomic accesses that address non-cached memory regions

Both are in realm of "Dear software, please, never do it. If you think
that you need it, you are wrong."
And in both cases it's not related to any sort timeout.

In case of Intel, I think that since Nehalem they don't have physical
Bus Lock signal in their processors.


Date Sujet#  Auteur
2 Sep 24 * arm ldxr/stxr vs cas58jseigh
2 Sep 24 +* Re: arm ldxr/stxr vs cas4Chris M. Thomasson
2 Sep 24 i`* Re: arm ldxr/stxr vs cas3Chris M. Thomasson
2 Sep 24 i `* Re: arm ldxr/stxr vs cas2jseigh
2 Sep 24 i  `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
4 Sep 24 +* Re: arm ldxr/stxr vs cas50MitchAlsup1
5 Sep 24 i+* Re: arm ldxr/stxr vs cas3Chris M. Thomasson
5 Sep 24 ii`* Re: arm ldxr/stxr vs cas2MitchAlsup1
5 Sep 24 ii `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
5 Sep 24 i`* Re: arm ldxr/stxr vs cas46jseigh
5 Sep 24 i +- Re: arm ldxr/stxr vs cas1Anton Ertl
5 Sep 24 i `* Re: arm ldxr/stxr vs cas44MitchAlsup1
5 Sep 24 i  `* Re: arm ldxr/stxr vs cas43Chris M. Thomasson
5 Sep 24 i   `* Re: arm ldxr/stxr vs cas42jseigh
6 Sep 24 i    +- Re: arm ldxr/stxr vs cas1MitchAlsup1
6 Sep 24 i    +* Re: arm ldxr/stxr vs cas20Chris M. Thomasson
6 Sep 24 i    i`* Re: arm ldxr/stxr vs cas19MitchAlsup1
7 Sep 24 i    i `* Re: arm ldxr/stxr vs cas18jseigh
8 Sep 24 i    i  `* Re: arm ldxr/stxr vs cas17Chris M. Thomasson
8 Sep 24 i    i   `* Re: arm ldxr/stxr vs cas16Chris M. Thomasson
8 Sep 24 i    i    `* Re: arm ldxr/stxr vs cas15Chris M. Thomasson
8 Sep 24 i    i     `* Re: arm ldxr/stxr vs cas14MitchAlsup1
8 Sep 24 i    i      +* Re: arm ldxr/stxr vs cas4Chris M. Thomasson
8 Sep 24 i    i      i+- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
8 Sep 24 i    i      i`* Re: arm ldxr/stxr vs cas2jseigh
8 Sep 24 i    i      i `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
8 Sep 24 i    i      `* Re: arm ldxr/stxr vs cas9Chris M. Thomasson
8 Sep 24 i    i       +* Re: arm ldxr/stxr vs cas6Michael S
8 Sep 24 i    i       i+- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
8 Sep 24 i    i       i+- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
9 Sep 24 i    i       i`* Re: arm ldxr/stxr vs cas3Michael S
9 Sep 24 i    i       i `* Re: arm ldxr/stxr vs cas2Michael S
9 Sep 24 i    i       i  `- Re: arm ldxr/stxr vs cas1Michael S
8 Sep 24 i    i       +- Re: arm ldxr/stxr vs cas1MitchAlsup1
8 Sep 24 i    i       `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
9 Sep 24 i    `* Re: arm ldxr/stxr vs cas20Terje Mathisen
9 Sep 24 i     +* Re: arm ldxr/stxr vs cas11jseigh
9 Sep 24 i     i+* Re: arm ldxr/stxr vs cas6Chris M. Thomasson
10 Sep 24 i     ii`* Re: arm ldxr/stxr vs cas5jseigh
10 Sep 24 i     ii `* Re: arm ldxr/stxr vs cas4Chris M. Thomasson
10 Sep 24 i     ii  `* Re: arm ldxr/stxr vs cas3jseigh
11 Sep 24 i     ii   `* Re: arm ldxr/stxr vs cas2Chris M. Thomasson
11 Sep 24 i     ii    `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
10 Sep 24 i     i`* Re: arm ldxr/stxr vs cas4Terje Mathisen
10 Sep 24 i     i `* Re: arm ldxr/stxr vs cas3jseigh
10 Sep 24 i     i  +- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
10 Sep 24 i     i  `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
9 Sep 24 i     +- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
11 Sep 24 i     `* Re: arm ldxr/stxr vs cas7Paul A. Clayton
11 Sep 24 i      +* Re: arm ldxr/stxr vs cas2Chris M. Thomasson
11 Sep 24 i      i`- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
11 Sep 24 i      +* Re: arm ldxr/stxr vs cas2jseigh
11 Sep 24 i      i`- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
11 Sep 24 i      `* Re: arm ldxr/stxr vs cas2Stefan Monnier
12 Sep 24 i       `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson
9 Sep 24 `* Re: arm ldxr/stxr vs cas3jseigh
11 Sep 24  `* Re: arm ldxr/stxr vs cas2jseigh
11 Sep 24   `- Re: arm ldxr/stxr vs cas1Chris M. Thomasson

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