Commit graph

11 commits

Author SHA1 Message Date
Branden Brown
14be23e5b4 semaphore: cancel acquisition with a done context
When acquiring from a semaphore could proceed without contention, the
previous behavior was to always do so, even when the provided context
was done. This was the documented behavior, but it could lead to
confusion. It isn't much more expensive to check the context error, so
cancel acquisition if it's done.

Fixes golang/go#63615.

goos: linux
goarch: amd64
pkg: golang.org/x/sync/semaphore
cpu: 12th Gen Intel(R) Core(TM) i5-1235U
                                        │  old.bench  │             new.bench              │
                                        │   sec/op    │   sec/op     vs base               │
AcquireSeq/Weighted-acquire-1-1-1-12      26.45n ± 2%   27.25n ± 3%  +3.04% (p=0.001 n=20)
AcquireSeq/Weighted-acquire-2-1-1-12      26.96n ± 1%   27.12n ± 1%       ~ (p=0.104 n=20)
AcquireSeq/Weighted-acquire-16-1-1-12     26.07n ± 3%   27.48n ± 1%  +5.45% (p=0.000 n=20)
AcquireSeq/Weighted-acquire-128-1-1-12    26.19n ± 2%   27.24n ± 1%  +4.01% (p=0.000 n=20)
AcquireSeq/Weighted-acquire-2-2-1-12      25.61n ± 1%   25.99n ± 2%       ~ (p=0.066 n=20)
AcquireSeq/Weighted-acquire-16-2-8-12     209.6n ± 2%   211.0n ± 3%       ~ (p=0.280 n=20)
AcquireSeq/Weighted-acquire-128-2-64-12   1.669µ ± 1%   1.721µ ± 2%  +3.09% (p=0.000 n=20)
AcquireSeq/Weighted-acquire-2-1-2-12      51.08n ± 1%   53.03n ± 2%  +3.82% (p=0.000 n=20)
AcquireSeq/Weighted-acquire-16-8-2-12     52.48n ± 2%   53.66n ± 2%  +2.26% (p=0.028 n=20)
AcquireSeq/Weighted-acquire-128-64-2-12   52.27n ± 1%   53.71n ± 2%  +2.75% (p=0.000 n=20)
geomean                                   60.06n        61.69n       +2.71%

Change-Id: I0ae1a0bb6c027461ac1a9ee71c51efd8427ab308
Reviewed-on: https://go-review.googlesource.com/c/sync/+/536275
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
2024-03-04 17:26:02 +00:00
Dmitri Shuralyov
10739b037d all: update go directive to 1.18
Done with:

go get go@1.18
go mod tidy
go fix ./...

Using go1.21.3.

While here, simplify package syncmap by taking advantage of knowing
that all supported Go versions will have the go1.9 build constraint
satisfied.

For golang/go#60268.

Change-Id: Ic0f24ab13ada6839573e55beee5516c1a6c7f3cc
Reviewed-on: https://go-review.googlesource.com/c/sync/+/534220
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
2023-10-11 14:04:17 +00:00
Russ Cox
036812b2e8 all: go fmt ./...
Make all our package sources use Go 1.17 gofmt format
(adding //go:build lines).

Not strictly necessary but will avoid spurious changes
as files are edited.

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Change-Id: Ie3f0a5f80ab53b95a25db9ccfd9a3cc4ea7ff465
Reviewed-on: https://go-review.googlesource.com/c/sync/+/294370
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
2021-02-20 03:29:51 +00:00
徐志强
43a5402ce7 semaphore: unblock waiters when the front waiter cancels
When `Release`, if the remaining tokens are not enough for the front waiter, no waiters will be notified.

So if the canceled waiter is the front one, it should try to notify following waiters if there are remaining tokens.

I found this bug when implementing a cancelable rwmutex based on semaphore:

https://github.com/zhiqiangxu/util/blob/master/mutex/crwmutex.go

This bug can be verified by this test:

https://github.com/zhiqiangxu/util/blob/master/mutex/crwmutex_test.go#L43

Change-Id: Id8564976bd375a82c4fbc6cb08b0bb83118a346c
GitHub-Last-Rev: 29b6ff26bf779d23239cfe64a395378a9e41d1fc
GitHub-Pull-Request: golang/sync#10
Reviewed-on: https://go-review.googlesource.com/c/sync/+/223418
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
2020-03-17 01:50:54 +00:00
Jean de Klerk
112230192c semaphore: better error message when releasing more than held
Change-Id: Ibe69007b2d7565a33d9e64ae51142478f495509a
Reviewed-on: https://go-review.googlesource.com/c/sync/+/173377
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2019-04-23 02:48:10 +00:00
Jean de Klerk
37e7f081c4 semaphore: add more Acquire documentation
Change-Id: Ie64db438145a307ec8aef8fd412d445a2fe74d40
Reviewed-on: https://go-review.googlesource.com/c/136995
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2018-12-21 19:32:16 +00:00
Jean de Klerk
42b317875d all: remove x/net/context in favour of context
Change-Id: Idbfe40e7cb9f99ca3dc7d4c214de6b9e028eefb7
Reviewed-on: https://go-review.googlesource.com/c/148277
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2018-11-08 01:04:31 +00:00
Bryan C. Mills
fd80eb99c8 semaphore: add worker-pool example
I've commented several times in various forums that basically every
time I've seen the “worker goroutine” pattern in Go, there has turned
out to be a cleaner implementation using semaphores.

This change adds a simple such example. (For more complex usage, I
would generally pair the semaphore with an errgroup.Group.)

Change-Id: Ibf69ee761d14ba59c1acc6a2d595b4fcf0d8f6d6
Reviewed-on: https://go-review.googlesource.com/75170
Reviewed-by: Ross Light <light@google.com>
2017-11-01 21:47:15 +00:00
Jonathan Amsterdam
f52d1811a6 semaphore: make test time independent of GOMAXPROCS
TestWeighted's runtime was roughly proportional to the number of CPUs,
so it ran a long time on PPCs (160 CPUs).

Make the number of loops in the test an inverse function of the number
of CPUs, to keep the test short.

Change-Id: Id853dbb5e5e2f9fb95966d19ef0c511e3f8080e0
Reviewed-on: https://go-review.googlesource.com/43632
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2017-05-17 21:12:32 +00:00
Jonathan Amsterdam
de49d9dcd2 semaphore: avoid loop variable capture by closure
Change-Id: I21c5dc48ffe43aa27c50a42f9c9a01ac1f0c747c
Reviewed-on: https://go-review.googlesource.com/40991
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Glenn Lewis <gmlewis@google.com>
2017-04-18 21:08:38 +00:00
Jonathan Amsterdam
5a06fca2c3 semaphore: add a weighted semaphore implementation
This package provides a weighted semaphore that is context-aware.

The code is derived from a similar package inside Google.

Change-Id: Id1dad96d79e8ccfd289e4299e8265aa5bdad3a5b
Reviewed-on: https://go-review.googlesource.com/38298
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2017-03-17 23:16:01 +00:00