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Daniel S Fava 35455fff0e runtime: swap the order of raceacquire() and racerelease()
In chansend() and chanrecv() of chan.go, the order of calls to
raceacquire() and racerelease() was swapped, which meant that the
code was not following the memory model "by the letter of the law."
Similar for bufrecv and bufsend in select.go

The memory model says:

- A send happens before the corresponding receive completes, and
- the kth receive on a channel with capacity C happens before the
k+C send on that channel completes.

The operative word here is "completes."  For example, a sender obtains
happens-before information on completion of the send-operation, which
means, after the sender has deposited its message onto the channel.
Similarly for receives.

If the order of raceacquire() and racerelease() is incorrect, the race
detector may fail to report some race conditions.

The fix is minimal from the point of view of Go.  The fix does, however,
rely on a new function added to TSan:

https://reviews.llvm.org/D76322

This commit only affects execution when race detection is enabled.

Added two tests into `runtime/race/output_test.go`:

- `chanmm` tests for the issue addressed by this patch
- `mutex` is a test for inverted semaphores, which must not be broken
  by this (or any other) patch

Fixes #37355

Change-Id: I5e886879ead2bd456a4b7dd1d17253641b767f63
Reviewed-on: https://go-review.googlesource.com/c/go/+/220419
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
2020-11-13 15:00:23 +00:00
.github .github: add link to questions in ISSUE_TEMPLATE 2020-01-06 17:05:31 +00:00
api api: update next.txt 2020-10-29 20:51:49 +00:00
doc doc/go1.16: add crypto/x509 CSR release note 2020-11-11 17:12:34 +00:00
lib/time lib/time, time/tzdata: update tz data to 2020d 2020-10-24 21:42:44 +00:00
misc cmd/go, cmd/cgo: don't let bogus symbol set cgo_ldflag 2020-11-12 20:58:06 +00:00
src runtime: swap the order of raceacquire() and racerelease() 2020-11-13 15:00:23 +00:00
test cmd/compile: make sure linkname'd symbol is non-package 2020-11-09 16:09:16 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: add Kush Patel (corporate CLA for Hootsuite Inc) 2020-07-08 00:10:44 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS CONTRIBUTORS: update for the Go 1.15 release 2020-08-10 21:51:48 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE
PATENTS
README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
robots.txt
SECURITY.md SECURITY.md: update go versions 2019-09-26 15:34:57 +00:00

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