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Austin Clements 18a13d373a [release-branch.go1.8] runtime: doubly fix "double wakeup" panic
Cherry-pick of CL 43311.

runtime.gchelper depends on the non-atomic load of work.ndone
happening strictly before the atomic add of work.nwait. Until very
recently (commit 978af9c2db, fixing #20334), the compiler reordered
these operations. This created a race since work.ndone can change as
soon as work.nwait is equal to work.ndone. If that happened, more than
one gchelper could attempt to wake up the work.alldone note, causing a
"double wakeup" panic.

This was fixed in the compiler, but to make this code less subtle,
make the load of work.ndone atomic. This clearly forces the order of
these operations, ensuring the race doesn't happen.

Fixes #19305 (though really 978af9c2db fixed it).

Change-Id: Ieb1a84e1e5044c33ac612c8a5ab6297e7db4c57d
Reviewed-on: https://go-review.googlesource.com/43412
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2017-05-23 19:42:13 +00:00
.github doc: improve issue template 2016-08-29 03:33:28 +00:00
api Revert "cmd/go: note when some Go files were ignored on no-Go-files errors" 2016-12-21 05:25:57 +00:00
doc [release-branch.go1.8] doc: remove mentions of yacc tool 2017-05-23 19:41:10 +00:00
lib/time lib/time: update tzdata to 2016j 2017-01-05 01:00:53 +00:00
misc [release-branch.go1.8] cmd/link: make mach-o dwarf segment properly aligned 2017-04-05 16:58:33 +00:00
src [release-branch.go1.8] runtime: doubly fix "double wakeup" panic 2017-05-23 19:42:13 +00:00
test [release-branch.go1.8] cmd/compile: added special case for reflect header fields to esc 2017-04-05 19:28:05 +00:00
.gitattributes
.gitignore .gitignore: fix attempt at rooted paths 2017-01-05 01:29:25 +00:00
AUTHORS A+C: automated update 2016-12-21 03:22:22 +00:00
CONTRIBUTING.md doc: update CONTRIBUTING.md a bit, mention proposal process 2017-01-06 23:19:01 +00:00
CONTRIBUTORS A+C: automated update 2016-12-21 03:22:22 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md README.md: update and simplify 2017-01-17 21:26:43 +00:00
VERSION [release-branch.go1.8] go1.8.2 2017-05-23 18:32:59 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
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README.md

The Go Programming Language

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