Remove unnecessary race.Release annotation from Unlock.
For RWMutex we want to establish the following happens-before (HB) edges:
1. Between Unlock and the subsequent Lock.
2. Between Unlock and the subsequent RLock.
3. Between batch of RUnlock's and the subsequent Lock.
1 is provided by Release(&rw.readerSem) in Unlock and Acquire(&rw.readerSem) in Lock.
2 is provided by Release(&rw.readerSem) in Unlock and Acquire(&rw.readerSem) in RLock.
3 is provided by ReleaseMerge(&rw.writerSem) in RUnlock in Acquire(&rw.writerSem) in Lock,
since we want to establish HB between a batch of RUnlock's this uses ReleaseMerge instead of Release.
Release(&rw.writerSem) in Unlock is simply not needed.
FWIW this is also how C++ tsan handles mutexes, not a proof but at least something.
Making 2 implementations consistent also simplifies any kind of reasoning against both of them.
Since this only affects performance, a reasonable test is not possible.
Everything should just continue to work but slightly faster.
Credit for discovering this goes to Jamie Liu.
Change-Id: Ice37d29ecb7a5faed3f7781c38dd32c7469b2735
Reviewed-on: https://go-review.googlesource.com/120495
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
We need to yield to the runtime every now and again to avoid
deadlock. This doesn't show up on most machines because the test
only runs when you have 5 or more CPUs.
Fixes#20072.
Change-Id: Ibf5ed370e919943395f3418487188df0b2be160b
Reviewed-on: https://go-review.googlesource.com/112978
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The implementation of atomics are inherently tricky. It would
be good to have them implemented in a single place, instead of
multiple copies.
Mostly a simple redirect.
On 386, some functions in sync/atomic have better implementations,
which are moved to runtime/internal/atomic.
On ARM, some functions in sync/atomic have better implementations.
They are dropped by this CL, but restored with an improved
version in a follow-up CL. On linux/arm, 64-bit CAS kernel helper
is dropped, as we're trying to move away from kernel helpers.
Fixes#23778.
Change-Id: Icb9e1039acc92adbb2a371c34baaf0b79551c3ea
Reviewed-on: https://go-review.googlesource.com/93637
Reviewed-by: Austin Clements <austin@google.com>
The test wants to check that copies of Cond are detected at runtime.
Make a copy that isn't detected by vet at compile time.
Change-Id: I933ab1003585f75ba96723563107f1ba8126cb72
Reviewed-on: https://go-review.googlesource.com/108557
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Previously these examples declared "var v Value" but any caller would
need to write "var v atomic.Value", so we should use the external
package declaration form to avoid confusion about where Value comes
from.
Change-Id: Ic0b1a05fb6b700da61cfc8efca594c49a9bedb69
Reviewed-on: https://go-review.googlesource.com/107975
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
For each replacement, test case is added to new 386enc.s file
with exception of EMMS, SYSENTER, MFENCE and LFENCE as they
are already covered in amd64enc.s (same on amd64 and 386).
The replacement became less obvious after go vet suggested changes
Before:
BYTE $0x0f; BYTE $0x7f; BYTE $0x44; BYTE $0x24; BYTE $0x08
Changed to MOVQ (this form is being tested):
MOVQ M0, 8(SP)
Refactored to FP-relative access (go vet advice):
MOVQ M0, val+4(FP)
Change-Id: I56b87cf3371b6ad81ad0cd9db2033aee407b5818
Reviewed-on: https://go-review.googlesource.com/101475
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
The struct stores its 64-bit state field in a 12-byte array to
ensure that it can be 64-bit-aligned. This leaves 4 spare bytes,
which we can reuse to store the sema field.
(32-bit alignment is still guaranteed because the array type was
changed to [3]uint32.)
Fixes#19149.
Change-Id: I9bc20e69e45e0e07fbf496080f3650e8be0d6e8d
Reviewed-on: https://go-review.googlesource.com/100515
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Include reader / writer interactions of RWMutex in the mutex profile.
Writer contention is already included in the profile, since a plain Mutex
is used to control exclusion.
Fixes#18496
Change-Id: Ib0dc1ffa0fd5e6d964a6f7764d7f09556eb63f00
Reviewed-on: https://go-review.googlesource.com/87095
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>
This replaces frame size -4 with the NOFRAME flag in arm assembly.
This was automated with:
sed -i -e 's/\(^TEXT.*[A-Z]\),\( *\)\$-4/\1|NOFRAME,\2$0/' $(find -name '*_arm.s')
Plus three manual comment changes found by:
grep '\$-4' $(find -name '*_arm.s')
The go binary is identical before and after this change.
Change-Id: I0310384d1a584118c41d1cd3a042bb8ea7227ef9
Reviewed-on: https://go-review.googlesource.com/92042
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
We used a mix of both before.
I've never heard anybody say "an arr-double you mutex" when speaking.
Fixes#23457
Change-Id: I802b5eb2339f885ca9d24607eeda565763165298
Reviewed-on: https://go-review.googlesource.com/87896
Reviewed-by: Andrew Bonventre <andybons@golang.org>
This was originally done in https://golang.org/cl/31359 but partially
undone (apparently unintentionally) in https://golang.org/cl/34310
Fix it, and update tests to ensure the error is unrecoverable.
Fixes#23039
Change-Id: I923ebd613a05e67d8acce77f4a68c64c8574faa6
Reviewed-on: https://go-review.googlesource.com/82656
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Values must not be copied after the first use.
Using noCopy makes vet complain about copies
even before the first use, which is incorrect
and very frustrating.
Drop it.
Fixes#21504.
Change-Id: Icd3a5ac3fe11e84525b998e848ed18a5d996f45a
Reviewed-on: https://go-review.googlesource.com/80836
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The go repository contains a mix of github.com/golang/go/issues/xxxxx
and golang.org/issues/xxxxx URLs for references to issues in the issue
tracker. We should use one for consistency, and golang.org is preferred
in case the project moves the issue tracker in the future.
This reasoning is taken from a comment Sam Whited left on a CL I
recently opened: https://go-review.googlesource.com/c/go/+/73890.
In that CL I referenced an issue using its github.com URL, because other
tests in the file I was changing contained references to issues using
their github.com URL. Sam Whited left a comment on the CL stating I
should change it to the golang.org URL.
If new code is intended to reference issues via golang.org and not
github.com, existing code should be updated so that precedence exists
for contributors who are looking at the existing code as a guide for the
code they should write.
Change-Id: I3b9053fe38a1c56fc101a8b7fd7b8f310ba29724
Reviewed-on: https://go-review.googlesource.com/75673
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
After switching to an iPhone 5 for the darwin/arm builds,
TestStoreLoadRelAcq32 started to timeout on every builder run.
Adding the same memory barriers as armLoadUint64 and armStoreUint64
makes the test complete successfully.
Fixes sync/atomic tests on the darwin/arm builder.
Change-Id: Id73de31679304e259bdbd7f2f94383ae7fd70ee4
Reviewed-on: https://go-review.googlesource.com/67390
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Found with mvdan.cc/unindent. It skipped the cases where parentheses
would need to be added, where comments would have to be moved elsewhere,
or where actions and simple logic would mix.
One of them was of the form "err != nil && err == io.EOF", so the first
part was removed.
Change-Id: Ie504c2b03a2c87d10ecbca1b9270069be1171b91
Reviewed-on: https://go-review.googlesource.com/57690
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Went mainly for the ones that make no sense, such as the ones
mid-sentence or after commas.
Change-Id: Ie245d2c19cc7428a06295635cf6a9482ade25ff0
Reviewed-on: https://go-review.googlesource.com/57293
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The tests were removed in https://golang.org/cl/2311 but some
references to them were missed.
Change-Id: I163e554a0cc99401a012deead8fda813ad74dbfe
Reviewed-on: https://go-review.googlesource.com/58870
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
From Josh's comments on https://golang.org/cl/50310
Once I removed the "from the Go standard library" bit, the beginning
wasn't worth keeping. It also wasn't clear whether what it meant by
"cache contention". Processor caches, or user-level caches built with
sync.Map? It didn't seem worth clarifying and didn't convey any useful
information, so deleted.
Change-Id: Id1d76105a3081d0855f6a64540700932bb83d98e
Reviewed-on: https://go-review.googlesource.com/50632
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
The mainline sync.Map has allowed mutations within Range callbacks
since https://golang.org/cl/37342. The reference implementations need
to do the same.
This change integrates https://go-review.googlesource.com/c/42956/
from x/sync.
Change-Id: I6b58cf874bb31cd4f6fdb8bfa8278888ed617a5a
Reviewed-on: https://go-review.googlesource.com/42957
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Local variables can also be relied on the be 64-bit aligned, since
they will be escaped to the heap if used with any atomic operations.
Also, allocated arrays are also aligned, just like structs and slices.
Fixes#18955.
Change-Id: I8a1897f6ff78922c8bfcf20d6eb4bcb17a70ba2d
Reviewed-on: https://go-review.googlesource.com/48112
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Prevent possible goroutine rescheduling to another P between
Put and Get calls by locking the goroutine to OS thread.
Inspired by the CL 42770.
Fixes#20198.
Change-Id: I18e24fcad1630658713e6b9d80d90d7941f604be
Reviewed-on: https://go-review.googlesource.com/44310
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This is a runtime version of sync.RWMutex that can be used by code in
the runtime package. The type is not quite the same, in that the zero
value is not valid.
For future use by CL 43713.
Updates #19546
Change-Id: I431eb3688add16ce1274dab97285f555b72735bf
Reviewed-on: https://go-review.googlesource.com/45991
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Remove note that sync.Cond, sync.Mutex, sync.RWMutex and atomic.Value
can be created as part of other data structures. Structs can be embedded
by default, and default should not be repeated.
Fixes#20471.
Change-Id: If3f5703d3f60abd96482b58ca43450d02a9e645a
Reviewed-on: https://go-review.googlesource.com/44071
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
LLV and SCV are 64-bit load-linked and store-conditional. They
were used in runtime as #define WORD. Change them to normal
instruction form.
NOOP is hardware no-op. It was written as WORD $0. Make a name
for it for better disassembly output.
Fixes#12561.
Fixes#18238.
Change-Id: I82c667ce756fa83ef37b034b641e8c4366335e83
Reviewed-on: https://go-review.googlesource.com/40297
Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
since there current version suffers from a copy'n'paste error.
Change-Id: I1ef97a4413198dde10c5c926a2a9806724cd6d44
Reviewed-on: https://go-review.googlesource.com/42095
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This is a direct port of the version from
commit a60ad46e0ed33d02e09bda439efaf9c9727dbc6c
(https://go-review.googlesource.com/c/37342/).
updates #17973
updates #18177
Change-Id: I63fa5ef6951b1edd39f84927d1181a4df9b15385
Reviewed-on: https://go-review.googlesource.com/36617
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Mostly unnecessary *testing.T arguments.
Found with github.com/mvdan/unparam.
Change-Id: Ifb955cb88f2ce8784ee4172f4f94d860fa36ae9a
Reviewed-on: https://go-review.googlesource.com/41691
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Make poolLocal size multiple of 128, so it aligns to CPU cache line
on the most common architectures.
This also has the following benefits:
- It may help compiler substituting integer multiplication
by bit shift inside indexLocal.
- It shrinks poolLocal size from 176 bytes to 128 bytes on amd64,
so now it fits two cache lines (or a single cache line on certain
Intel CPUs - see https://software.intel.com/en-us/articles/optimizing-application-performance-on-intel-coret-microarchitecture-using-hardware-implemented-prefetchers).
No measurable performance changes on linux/amd64 and linux/386.
Change-Id: I11df0f064718a662e77a85d88b8a15a8919f25e9
Reviewed-on: https://go-review.googlesource.com/40918
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Such dead code is legitimate when dealing with arch-specific
types (int, uint, uintptr).
The CL removes the majority of 'too small for shift' false positives
from such a code.
Change-Id: I62c5635a1d3774ab2d71d3d7056f0589f214cbe5
Reviewed-on: https://go-review.googlesource.com/38065
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Also runs 100X faster on average, because it takes so many
fewer attempts to trigger the failure.
Fixes#11443.
Change-Id: I8c39ee48bb3ff6c36fa63083e04076771b65a80d
Reviewed-on: https://go-review.googlesource.com/36841
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
It was a little tricky to figure out how to go from the documentation
to figuring out the best way to implement a Pool, so I thought I'd
try to provide a simple example. The implementation is mostly taken
from the fmt package.
I'm not happy with the verbosity of the calls to WriteString() etc,
but I wanted to provide a non-trivial example.
Change-Id: Id33a8b6cbf8eb278f71e1f78e20205b436578606
Reviewed-on: https://go-review.googlesource.com/24371
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
runtime.SetMutexProfileFraction(n int) will capture 1/n-th of stack
traces of goroutines holding contended mutexes if n > 0. From runtime/pprof,
pprot.Lookup("mutex").WriteTo writes the accumulated
stack traces to w (in essentially the same format that blocking
profiling uses).
Change-Id: Ie0b54fa4226853d99aa42c14cb529ae586a8335a
Reviewed-on: https://go-review.googlesource.com/29650
Reviewed-by: Austin Clements <austin@google.com>
