#
1.9 |
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09-Apr-2022 |
riastradh |
Introduce membar_acquire/release. Deprecate membar_enter/exit.
The names membar_enter/exit were unclear, and the documentation of membar_enter has disagreed with the implementations on sparc, powerpc, and even x86(!) for the entire time it has been in NetBSD.
The terms `acquire' and `release' are ubiquitous in the literature today, and have been adopted in the C and C++ standards to mean load-before-load/store and load/store-before-store, respectively, which are exactly the orderings required by acquiring and releasing a mutex, as well as other useful applications like decrementing a reference count and then freeing the underlying object if it went to zero.
Originally I proposed changing one word in the documentation for membar_enter to make it load-before-load/store instead of store-before-load/store, i.e., to make it an acquire barrier. I proposed this on the grounds that
(a) all implementations guarantee load-before-load/store, (b) some implementations fail to guarantee store-before-load/store, and (c) all uses in-tree assume load-before-load/store.
I verified parts (a) and (b) (except, for (a), powerpc didn't even guarantee load-before-load/store -- isync isn't necessarily enough; need lwsync in general -- but it _almost_ did, and it certainly didn't guarantee store-before-load/store).
Part (c) might not be correct, however: under the mistaken assumption that atomic-r/m/w then membar-w/rw is equivalent to atomic-r/m/w then membar-r/rw, I only audited the cases of membar_enter that _aren't_ immediately after an atomic-r/m/w. All of those cases assume load-before-load/store. But my assumption was wrong -- there are cases of atomic-r/m/w then membar-w/rw that would be broken by changing to atomic-r/m/w then membar-r/rw:
https://mail-index.netbsd.org/tech-kern/2022/03/29/msg028044.html
Furthermore, the name membar_enter has been adopted in other places like OpenBSD where it actually does follow the documentation and guarantee store-before-load/store, even if that order is not useful. So the name membar_enter currently lives in a bad place where it means either of two things -- r/rw or w/rw.
With this change, we deprecate membar_enter/exit, introduce membar_acquire/release as better names for the useful pair (r/rw and rw/w), and make sure the implementation of membar_enter guarantees both what was documented _and_ what was implemented, making it an alias for membar_sync.
While here, rework all of the membar_* definitions and aliases. The new logic follows a rule to make it easier to audit:
membar_X is defined as an alias for membar_Y iff membar_X is guaranteed by membar_Y.
The `no stronger than' relation is (the transitive closure of):
- membar_consumer (r/r) is guaranteed by membar_acquire (r/rw) - membar_producer (w/w) is guaranteed by membar_release (rw/w) - membar_acquire (r/rw) is guaranteed by membar_sync (rw/rw) - membar_release (rw/w) is guaranteed by membar_sync (rw/rw)
And, for the deprecated membars:
- membar_enter (whether r/rw, w/rw, or rw/rw) is guaranteed by membar_sync (rw/rw) - membar_exit (rw/w) is guaranteed by membar_release (rw/w)
(membar_exit is identical to membar_release, but the name is deprecated.)
Finally, while here, annotate some of the instructions with their semantics. For powerpc, leave an essay with citations on the unfortunate but -- as far as I can tell -- necessary decision to use lwsync, not isync, for membar_acquire and membar_consumer.
Also add membar(3) and atomic(3) man page links.
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#
1.8 |
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06-Apr-2022 |
riastradh |
Nix trailing whitespace in files of membars, atomics, and lock stubs.
Will be touching many of these files soon for functional changes.
No functional change intended.
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Revision tags: cjep_sun2x-base1 cjep_sun2x-base cjep_staticlib_x-base1 netbsd-9-2-RELEASE cjep_staticlib_x-base netbsd-9-1-RELEASE bouyer-xenpvh-base2 phil-wifi-20200421 bouyer-xenpvh-base1 bouyer-xenpvh-base phil-wifi-20200411 is-mlppp-base phil-wifi-20200406 netbsd-8-2-RELEASE ad-namecache-base3 netbsd-9-0-RELEASE netbsd-9-0-RC2 ad-namecache-base netbsd-9-0-RC1 phil-wifi-20191119 netbsd-9-base phil-wifi-20190609 netbsd-8-1-RELEASE netbsd-8-1-RC1 pgoyette-compat-merge-20190127 pgoyette-compat-20190127 pgoyette-compat-20190118 pgoyette-compat-1226 pgoyette-compat-1126 pgoyette-compat-1020 pgoyette-compat-0930 pgoyette-compat-0906 pgoyette-compat-0728 netbsd-8-0-RELEASE phil-wifi-base pgoyette-compat-0625 netbsd-8-0-RC2 pgoyette-compat-0521 pgoyette-compat-0502 pgoyette-compat-0422 netbsd-8-0-RC1 pgoyette-compat-0415 pgoyette-compat-0407 pgoyette-compat-0330 pgoyette-compat-0322 pgoyette-compat-0315 pgoyette-compat-base tls-maxphys-20171202 matt-nb8-mediatek-base perseant-stdc-iso10646-base netbsd-8-base prg-localcount2-base3 prg-localcount2-base2 prg-localcount2-base1 prg-localcount2-base pgoyette-localcount-20170426 bouyer-socketcan-base1 pgoyette-localcount-20170320 bouyer-socketcan-base pgoyette-localcount-20170107 pgoyette-localcount-20161104 localcount-20160914 pgoyette-localcount-20160806 pgoyette-localcount-20160726 pgoyette-localcount-base
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#
1.7 |
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08-Jan-2015 |
riastradh |
branches: 1.7.16; Introduce membar_datadep_consumer.
Discussed briefly on tech-kern without objection:
https://mail-index.netbsd.org/tech-kern/2014/11/20/msg018054.html https://mail-index.netbsd.org/tech-kern/2015/01/07/msg018326.html
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Revision tags: netbsd-5-2-3-RELEASE netbsd-5-1-5-RELEASE netbsd-6-0-6-RELEASE netbsd-6-1-5-RELEASE netbsd-7-base yamt-pagecache-base9 yamt-pagecache-tag8 netbsd-6-1-4-RELEASE netbsd-6-0-5-RELEASE tls-earlyentropy-base riastradh-xf86-video-intel-2-7-1-pre-2-21-15 riastradh-drm2-base3 netbsd-6-1-3-RELEASE netbsd-6-0-4-RELEASE netbsd-5-2-2-RELEASE netbsd-5-1-4-RELEASE netbsd-6-1-2-RELEASE netbsd-6-0-3-RELEASE netbsd-5-2-1-RELEASE netbsd-5-1-3-RELEASE rmind-smpnet-nbase netbsd-6-1-1-RELEASE riastradh-drm2-base2 riastradh-drm2-base1 riastradh-drm2-base rmind-smpnet-base netbsd-6-0-2-RELEASE netbsd-6-1-RELEASE netbsd-6-1-RC4 netbsd-6-1-RC3 agc-symver-base netbsd-6-1-RC2 netbsd-6-1-RC1 yamt-pagecache-base8 netbsd-6-0-1-RELEASE yamt-pagecache-base7 netbsd-5-2-RELEASE netbsd-5-2-RC1 matt-nb6-plus-nbase yamt-pagecache-base6 netbsd-6-0-RELEASE netbsd-6-0-RC2 tls-maxphys-base matt-nb6-plus-base netbsd-6-0-RC1 yamt-pagecache-base5 yamt-pagecache-base4 netbsd-6-base netbsd-5-1-2-RELEASE netbsd-5-1-1-RELEASE yamt-pagecache-base3 yamt-pagecache-base2 yamt-pagecache-base cherry-xenmp-base bouyer-quota2-nbase bouyer-quota2-base matt-mips64-premerge-20101231 matt-nb5-mips64-premerge-20101231 matt-nb5-pq3-base netbsd-5-1-RELEASE yamt-nfs-mp-base11 netbsd-5-1-RC4 matt-nb5-mips64-k15 yamt-nfs-mp-base10 netbsd-5-1-RC3 netbsd-5-1-RC2 netbsd-5-1-RC1 rmind-uvmplock-base yamt-nfs-mp-base9 netbsd-5-0-2-RELEASE matt-nb5-mips64-premerge-20091211 matt-premerge-20091211 yamt-nfs-mp-base8 matt-nb5-mips64-u2-k2-k4-k7-k8-k9 matt-nb4-mips64-k7-u2a-k9b matt-nb5-mips64-u1-k1-k5 yamt-nfs-mp-base7 netbsd-5-0-1-RELEASE jymxensuspend-base yamt-nfs-mp-base6 yamt-nfs-mp-base5 yamt-nfs-mp-base4 jym-xensuspend-nbase yamt-nfs-mp-base3 netbsd-5-0-RELEASE netbsd-5-0-RC4 netbsd-5-0-RC3 netbsd-5-0-RC2 jym-xensuspend-base netbsd-5-0-RC1 netbsd-5-base matt-mips64-base2 wrstuden-revivesa-base-3 wrstuden-revivesa-base-2 wrstuden-revivesa-base-1 yamt-pf42-base4 yamt-pf42-base3 wrstuden-revivesa-base
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#
1.6 |
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25-May-2008 |
chs |
branches: 1.6.40; enable profiling of assembly functions.
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Revision tags: hpcarm-cleanup-nbase yamt-pf42-base2 yamt-nfs-mp-base2
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#
1.5 |
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28-Apr-2008 |
martin |
branches: 1.5.2; Remove clause 3 and 4 from TNF licenses
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Revision tags: yamt-pf42-baseX yamt-nfs-mp-base yamt-pf42-base yamt-lazymbuf-base15 yamt-lazymbuf-base14 keiichi-mipv6-base matt-armv6-nbase hpcarm-cleanup-base
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#
1.4 |
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12-Feb-2008 |
ad |
branches: 1.4.4; Always enable memory barriers in userspace, otherwise libpthread won't work correctly on MP systems.
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#
1.3 |
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12-Feb-2008 |
matt |
Fix pthread problem. (export membar* to userland)
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Revision tags: matt-armv6-base yamt-kmem-base3 cube-autoconf-base yamt-kmem-base2 yamt-kmem-base reinoud-bufcleanup-nbase reinoud-bufcleanup-base
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#
1.2 |
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28-Nov-2007 |
ad |
branches: 1.2.4; Pull in alpha atomic ops from the thorpej-atomic branch.
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Revision tags: yamt-x86pmap-base4 yamt-x86pmap-base3 yamt-x86pmap-base2 yamt-x86pmap-base yamt-idlelwp-base8
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#
1.1 |
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18-Apr-2007 |
thorpej |
branches: 1.1.2; file membar_ops.S was initially added on branch thorpej-atomic.
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#
1.8 |
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06-Apr-2022 |
riastradh |
Nix trailing whitespace in files of membars, atomics, and lock stubs.
Will be touching many of these files soon for functional changes.
No functional change intended.
|
Revision tags: cjep_sun2x-base1 cjep_sun2x-base cjep_staticlib_x-base1 netbsd-9-2-RELEASE cjep_staticlib_x-base netbsd-9-1-RELEASE bouyer-xenpvh-base2 phil-wifi-20200421 bouyer-xenpvh-base1 bouyer-xenpvh-base phil-wifi-20200411 is-mlppp-base phil-wifi-20200406 netbsd-8-2-RELEASE ad-namecache-base3 netbsd-9-0-RELEASE netbsd-9-0-RC2 ad-namecache-base netbsd-9-0-RC1 phil-wifi-20191119 netbsd-9-base phil-wifi-20190609 netbsd-8-1-RELEASE netbsd-8-1-RC1 pgoyette-compat-merge-20190127 pgoyette-compat-20190127 pgoyette-compat-20190118 pgoyette-compat-1226 pgoyette-compat-1126 pgoyette-compat-1020 pgoyette-compat-0930 pgoyette-compat-0906 pgoyette-compat-0728 netbsd-8-0-RELEASE phil-wifi-base pgoyette-compat-0625 netbsd-8-0-RC2 pgoyette-compat-0521 pgoyette-compat-0502 pgoyette-compat-0422 netbsd-8-0-RC1 pgoyette-compat-0415 pgoyette-compat-0407 pgoyette-compat-0330 pgoyette-compat-0322 pgoyette-compat-0315 pgoyette-compat-base tls-maxphys-20171202 matt-nb8-mediatek-base perseant-stdc-iso10646-base netbsd-8-base prg-localcount2-base3 prg-localcount2-base2 prg-localcount2-base1 prg-localcount2-base pgoyette-localcount-20170426 bouyer-socketcan-base1 pgoyette-localcount-20170320 bouyer-socketcan-base pgoyette-localcount-20170107 pgoyette-localcount-20161104 localcount-20160914 pgoyette-localcount-20160806 pgoyette-localcount-20160726 pgoyette-localcount-base
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#
1.7 |
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08-Jan-2015 |
riastradh |
branches: 1.7.16; Introduce membar_datadep_consumer.
Discussed briefly on tech-kern without objection:
https://mail-index.netbsd.org/tech-kern/2014/11/20/msg018054.html https://mail-index.netbsd.org/tech-kern/2015/01/07/msg018326.html
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Revision tags: netbsd-5-2-3-RELEASE netbsd-5-1-5-RELEASE netbsd-6-0-6-RELEASE netbsd-6-1-5-RELEASE netbsd-7-base yamt-pagecache-base9 yamt-pagecache-tag8 netbsd-6-1-4-RELEASE netbsd-6-0-5-RELEASE tls-earlyentropy-base riastradh-xf86-video-intel-2-7-1-pre-2-21-15 riastradh-drm2-base3 netbsd-6-1-3-RELEASE netbsd-6-0-4-RELEASE netbsd-5-2-2-RELEASE netbsd-5-1-4-RELEASE netbsd-6-1-2-RELEASE netbsd-6-0-3-RELEASE netbsd-5-2-1-RELEASE netbsd-5-1-3-RELEASE rmind-smpnet-nbase netbsd-6-1-1-RELEASE riastradh-drm2-base2 riastradh-drm2-base1 riastradh-drm2-base rmind-smpnet-base netbsd-6-0-2-RELEASE netbsd-6-1-RELEASE netbsd-6-1-RC4 netbsd-6-1-RC3 agc-symver-base netbsd-6-1-RC2 netbsd-6-1-RC1 yamt-pagecache-base8 netbsd-6-0-1-RELEASE yamt-pagecache-base7 netbsd-5-2-RELEASE netbsd-5-2-RC1 matt-nb6-plus-nbase yamt-pagecache-base6 netbsd-6-0-RELEASE netbsd-6-0-RC2 tls-maxphys-base matt-nb6-plus-base netbsd-6-0-RC1 yamt-pagecache-base5 yamt-pagecache-base4 netbsd-6-base netbsd-5-1-2-RELEASE netbsd-5-1-1-RELEASE yamt-pagecache-base3 yamt-pagecache-base2 yamt-pagecache-base cherry-xenmp-base bouyer-quota2-nbase bouyer-quota2-base matt-mips64-premerge-20101231 matt-nb5-mips64-premerge-20101231 matt-nb5-pq3-base netbsd-5-1-RELEASE yamt-nfs-mp-base11 netbsd-5-1-RC4 matt-nb5-mips64-k15 yamt-nfs-mp-base10 netbsd-5-1-RC3 netbsd-5-1-RC2 netbsd-5-1-RC1 rmind-uvmplock-base yamt-nfs-mp-base9 netbsd-5-0-2-RELEASE matt-nb5-mips64-premerge-20091211 matt-premerge-20091211 yamt-nfs-mp-base8 matt-nb5-mips64-u2-k2-k4-k7-k8-k9 matt-nb4-mips64-k7-u2a-k9b matt-nb5-mips64-u1-k1-k5 yamt-nfs-mp-base7 netbsd-5-0-1-RELEASE jymxensuspend-base yamt-nfs-mp-base6 yamt-nfs-mp-base5 yamt-nfs-mp-base4 jym-xensuspend-nbase yamt-nfs-mp-base3 netbsd-5-0-RELEASE netbsd-5-0-RC4 netbsd-5-0-RC3 netbsd-5-0-RC2 jym-xensuspend-base netbsd-5-0-RC1 netbsd-5-base matt-mips64-base2 wrstuden-revivesa-base-3 wrstuden-revivesa-base-2 wrstuden-revivesa-base-1 yamt-pf42-base4 yamt-pf42-base3 wrstuden-revivesa-base
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#
1.6 |
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25-May-2008 |
chs |
branches: 1.6.40; enable profiling of assembly functions.
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Revision tags: hpcarm-cleanup-nbase yamt-pf42-base2 yamt-nfs-mp-base2
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#
1.5 |
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28-Apr-2008 |
martin |
branches: 1.5.2; Remove clause 3 and 4 from TNF licenses
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Revision tags: yamt-pf42-baseX yamt-nfs-mp-base yamt-pf42-base yamt-lazymbuf-base15 yamt-lazymbuf-base14 keiichi-mipv6-base matt-armv6-nbase hpcarm-cleanup-base
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#
1.4 |
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12-Feb-2008 |
ad |
branches: 1.4.4; Always enable memory barriers in userspace, otherwise libpthread won't work correctly on MP systems.
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#
1.3 |
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12-Feb-2008 |
matt |
Fix pthread problem. (export membar* to userland)
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Revision tags: matt-armv6-base yamt-kmem-base3 cube-autoconf-base yamt-kmem-base2 yamt-kmem-base reinoud-bufcleanup-nbase reinoud-bufcleanup-base
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#
1.2 |
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28-Nov-2007 |
ad |
branches: 1.2.4; Pull in alpha atomic ops from the thorpej-atomic branch.
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Revision tags: yamt-x86pmap-base4 yamt-x86pmap-base3 yamt-x86pmap-base2 yamt-x86pmap-base yamt-idlelwp-base8
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#
1.1 |
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18-Apr-2007 |
thorpej |
branches: 1.1.2; file membar_ops.S was initially added on branch thorpej-atomic.
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#
1.7 |
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08-Jan-2015 |
riastradh |
Introduce membar_datadep_consumer.
Discussed briefly on tech-kern without objection:
https://mail-index.netbsd.org/tech-kern/2014/11/20/msg018054.html https://mail-index.netbsd.org/tech-kern/2015/01/07/msg018326.html
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#
1.6 |
|
25-May-2008 |
chs |
branches: 1.6.40; enable profiling of assembly functions.
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#
1.5 |
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28-Apr-2008 |
martin |
branches: 1.5.2; Remove clause 3 and 4 from TNF licenses
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#
1.4 |
|
12-Feb-2008 |
ad |
branches: 1.4.4; Always enable memory barriers in userspace, otherwise libpthread won't work correctly on MP systems.
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#
1.3 |
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12-Feb-2008 |
matt |
Fix pthread problem. (export membar* to userland)
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#
1.2 |
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27-Nov-2007 |
ad |
branches: 1.2.4; Pull in alpha atomic ops from the thorpej-atomic branch.
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#
1.1 |
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17-Apr-2007 |
thorpej |
branches: 1.1.2; file membar_ops.S was initially added on branch thorpej-atomic.
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#
1.1.2.2 |
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21-Apr-2007 |
thorpej |
Make sure namespace-cleansed aliases are avaialble for all atomic ops.
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#
1.1.2.1 |
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17-Apr-2007 |
thorpej |
Atomic op implementation for Alpha.
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#
1.2.4.3 |
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22-Mar-2008 |
matt |
sync with HEAD
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#
1.2.4.2 |
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08-Jan-2008 |
matt |
sync with HEAD
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#
1.2.4.1 |
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27-Nov-2007 |
matt |
file membar_ops.S was added on branch matt-armv6 on 2008-01-09 01:20:51 +0000
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#
1.4.4.2 |
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03-Jun-2008 |
yamt |
sync with head
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#
1.4.4.1 |
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18-May-2008 |
yamt |
sync with head.
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#
1.5.2.1 |
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22-Jun-2008 |
wrstuden |
Sync w/ -current. 34 merge conflicts to follow.
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#
1.6.40.1 |
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18-Mar-2015 |
snj |
Pull up following revision(s) (requested by riastradh in ticket #600): common/lib/libc/arch/alpha/atomic/membar_ops.S: revision 1.7 lib/libc/atomic/membar_ops.3: revision 1.4 sys/arch/alpha/include/types.h: revision 1.50 sys/sys/atomic.h: revision 1.13 Introduce membar_datadep_consumer. Discussed briefly on tech-kern without objection: https://mail-index.netbsd.org/tech-kern/2014/11/20/msg018054.html https://mail-index.netbsd.org/tech-kern/2015/01/07/msg018326.html
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