This adds the three functions from #56102 to the sync package. These
provide a convenient API for the most common uses of sync.Once.
The performance of these is comparable to direct use of sync.Once:
$ go test -run ^$ -bench OnceFunc\|OnceVal -count 20 | benchstat -row .name -col /v
goos: linux
goarch: amd64
pkg: sync
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
│ Once │ Global │ Local │
│ sec/op │ sec/op vs base │ sec/op vs base │
OnceFunc 1.3500n ± 6% 2.7030n ± 1% +100.22% (p=0.000 n=20) 0.3935n ± 0% -70.86% (p=0.000 n=20)
OnceValue 1.3155n ± 0% 2.7460n ± 1% +108.74% (p=0.000 n=20) 0.5478n ± 1% -58.35% (p=0.000 n=20)
The "Once" column represents the baseline of how code would typically
express these patterns using sync.Once. "Global" binds the closure
returned by OnceFunc/OnceValue to global, which is how I expect these
to be used most of the time. Currently, this defeats some inlining
opportunities, which roughly doubles the cost over sync.Once; however,
it's still *extremely* fast. Finally, "Local" binds the returned
closure to a local variable. This unlocks several levels of inlining
and represents pretty much the best possible case for these APIs, but
is also unlikely to happen in practice. In principle the compiler
could recognize that the global in the "Global" case is initialized in
place and never mutated and do the same optimizations it does in the
"Local" case, but it currently does not.
Fixes#56102
Change-Id: If7355eccd7c8de7288d89a4282ff15ab1469e420
Reviewed-on: https://go-review.googlesource.com/c/go/+/451356
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Reviewed-by: Caleb Spare <cespare@gmail.com>
Auto-Submit: Austin Clements <austin@google.com>
I noticed the one in path/filepath while reading the docs,
and the other ones were found via some quick grepping.
Change-Id: I386f2f74ef816a6d18aa2f58ee6b64dbd0147c9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/478795
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
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These functions are linked using go:linkname, but do not match the
original declarations. This change brings these in sync.
Change-Id: I16651304c3dba2f9897c2c42e30555d2f7805c2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/466615
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
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Auto-Submit: Michael Pratt <mpratt@google.com>
CL 381316 documented the memory model of Map's APIs. However, the newly
introduced Swap, CompareAndSwap, and CompareAndDelete are missing from
this documentation as CL 399094 did not add this info.
This CL specifies the defined read/write operations of the new Map APIs.
For #51972
Change-Id: I519a04040a0b429a3f978823a183cd62e42c90ae
Reviewed-on: https://go-review.googlesource.com/c/go/+/459715
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Reviewed-by: Bryan Mills <bcmills@google.com>
For #56603, CL 448275 added a _ [0]T field to atomic.Pointer,
so that different kinds of atomic.Pointer are not convertible.
Unfortunately, that breaks code like:
type List struct {
Next atomic.Pointer[List]
}
which should be valid, just as using Next *List is valid.
Instead, we get:
./atomic_test.go:2533:6: invalid recursive type List
./atomic_test.go:2533:6: List refers to
./atomic_test.go:2534:13: "sync/atomic".Pointer refers to
./atomic_test.go:2533:6: List
Fix by using _[0]*T instead.
Change-Id: Icc4c83c691d35961d20cb14b824223d6c779ac5e
Reviewed-on: https://go-review.googlesource.com/c/go/+/450655
Run-TryBot: Russ Cox <rsc@golang.org>
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Rename "ifaceWords" to "efaceWords", since we are defining
an empty interface.
Change-Id: I7151fb730a081a800e6dd28bcba831787ee9d6a2
Reviewed-on: https://go-review.googlesource.com/c/go/+/432815
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: hopehook <hopehook@golangcn.org>
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Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
The previous wording was unclear and seemingly contradictory.
Change-Id: I0781dc4525948f4e8e5698271362a82387688f81
GitHub-Last-Rev: c1e032fa94
GitHub-Pull-Request: golang/go#53516
Reviewed-on: https://go-review.googlesource.com/c/go/+/413774
Reviewed-by: Ian Lance Taylor <iant@google.com>
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This change adds 3 new waitReasons that correspond to sync.Mutex.Lock,
sync.RWMutex.RLock, and sync.RWMutex.Lock that are plumbed down into
semacquire1 by exporting new functions to the sync package from the
runtime.
Currently these three functions show up as "semacquire" in backtraces
which isn't very clear, though the stack trace itself should reveal
what's really going on. This represents a minor improvement to backtrace
readability, though blocking on an RWMutex.w.Lock will still show up as
blocking on a regular mutex (I suppose technically it is).
This is a step toward helping the runtime identify when a goroutine is
blocked on a mutex of some kind.
For #49881.
Change-Id: Ia409b4d27e117fe4bfdc25fa541e9c58d6d587b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/427616
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The "&x.v" cost us 2 inline cost budget, causing extra inline cost for
the caller. By taking the fact that "v" is laid out in memory as the
first field of all atomic types, we can accessing it without addressing.
Discovering why attempting to convert sync.RWMutex.readerCount to atomic
type. RWMutex.RUnlock have the inline cost 75, with extra 7 inline cost
from Int32.Add causing it not inlinable anymore.
With this change, Int32.Add only has 5 inline cost budget, RWMutex can
use it while still be inlinable.
Change-Id: Iabe1d1bf53389b0b8b5f56b4611231b732fd9df5
Reviewed-on: https://go-review.googlesource.com/c/go/+/429766
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Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This reverts commit CL 427140.
Reason for revert: Comments say that done should be the first field.
Change-Id: Id131da064146b44e1182289546aeb877867e63cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/428638
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Change-Id: I49f8c764d49cabaad4d6859c219ba7220a389c1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/427140
Run-TryBot: xie cui <523516579@qq.com>
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Reviewed-by: Michael Knyszek <mknyszek@google.com>
Cond is difficult to use correctly (I was just bitten by it in
a production app that I inherited). While several proposals have come
up to improve or remove sync.Cond, no action has so far been taken.
Update the documentation to discourage use of sync.Cond, and point
people in the direction of preferred alternatives. I believe this will
help encourage behavior we want (less use of sync.Cond and more use of
channels), while also paving the way for, potentially, removing Cond
in a future version of the language.
Thanks very much to Bryan Mills and Sean Liao for discussion and
recommendations.
Updates #20491.
Updates #21165.
Change-Id: Ib4d0631c79d4c4d0a30027255cd43bc47cddebd3
Reviewed-on: https://go-review.googlesource.com/c/go/+/412237
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This test originally existed as two tests in test/locklinear.go, but
this checked against actual locks and was flaky. The test was checking
a property of a deep part of the runtime but from a much higher level,
and it's easy for nondeterminism due to scheduling to completely mess
that up, especially on an oversubscribed system.
That test was then moved to the sync package with a more rigorous
testing methodology, but it could still flake pretty easily.
Finally, this CL makes semtable more testable, exports it in
export_test.go, then writes a very direct scalability test for exactly
the situation the original test described. As far as I can tell, this is
much, much more stable, because it's single-threaded and is just
checking exactly the algorithm we need to check.
Don't bother trying to bring in a test that checks for O(log n) behavior
on the other kind of iteration. It'll be perpetually flaky because the
underlying data structure is a treap, so it's only _expected_ to be
O(log n), but it's very easy for it to get unlucky without a large
number of iterations that's too much for a simple test.
Fixes#53381.
Change-Id: Ia1cd2d2b0e36d552d5a8ae137077260a16016602
Reviewed-on: https://go-review.googlesource.com/c/go/+/412875
Reviewed-by: Michael Pratt <mpratt@google.com>
This change improves the robustness of the locklinear test in the
following ways:
* It removes allocations from the timing, which may be very variable if
we're unlucky.
* It ensures that goroutines are properly cleaned up before the test
function returns, reducing the chance that they bleed into repeat
attempts. It also stops timing before this cleanup.
Fixes#32986.
Change-Id: I3a8096e6922f23d899ad602e2845bdfc639ed742
Reviewed-on: https://go-review.googlesource.com/c/go/+/409894
Reviewed-by: Michael Pratt <mpratt@google.com>
This change moves test/locklinear.go into the sync package tests, and
adds a bit of infrastructure since there are other linearity-checking
tests that could benefit from it too. This infrastructure is also
different than what test/locklinear.go does: instead of trying really
hard to get at least one success, we instead treat this like a
performance test and look for a significant difference via a t-test.
This makes the methodology behind the tests more rigorous, and should
reduce flakiness as transient noise should produce an insignificant
result. A follow-up CL does more to make these tests even more robust.
For #32986.
Change-Id: I408c5f643962b70ea708930edb4ac9df1c6123ce
Reviewed-on: https://go-review.googlesource.com/c/go/+/411396
Reviewed-by: Michael Pratt <mpratt@google.com>
A few of these are copied from the memory model doc.
Many are entirely new, following discussion on #47141.
See https://research.swtch.com/gomm for background.
The rule we are establishing is that each type that is meant
to help synchronize a Go program should document its
happens-before guarantees.
For #50859.
Change-Id: I947c40639b263abe67499fa74f68711a97873a39
Reviewed-on: https://go-review.googlesource.com/c/go/+/381316
Auto-Submit: Russ Cox <rsc@golang.org>
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Reviewed-by: Roland Shoemaker <roland@golang.org>
Excluding vendor and testdata.
CL 384268 already reformatted most, but these slipped past.
The struct in the doc comment in debug/dwarf/type.go
was fixed up by hand to indent the first and last lines as well.
For #51082.
Change-Id: Iad020f83aafd671ff58238fe491907e85923d0c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/407137
Run-TryBot: Russ Cox <rsc@golang.org>
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When the procUnpin is placed after shared.pushHead, there is
no need for x as a flag to indicate the previous process.
This CL can make the logic clear, and at the same time reduce
a redundant judgment.
Change-Id: I34ec9ba4cb5b5dbdf13a8f158b90481fed248cf5
Reviewed-on: https://go-review.googlesource.com/c/go/+/360059
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Auto-Submit: Ian Lance Taylor <iant@google.com>
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The tests don't work on big-endian systems. This change handles more
of the tests added in CL 381317 like the other existing tests.
Fixes#52723
Change-Id: Ie9e048e75dbe0b5aca61b51cd0c50d7d878ff6d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/404495
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These implementations will inline to the lower-level primitives,
but they hide the underlying values so that all accesses are
forced to use the atomic APIs. They also allow the use of shorter
names (methods instead of functions) at call sites, making code
more readable.
Pointer[T] also avoids conversions using unsafe.Pointer at call sites.
Discussed on #47141.
See also https://research.swtch.com/gomm for background.
Fixes#50860.
Change-Id: I0b178ee0c7747fa8985f8e48cd7b01063feb7dcc
Reviewed-on: https://go-review.googlesource.com/c/go/+/381317
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
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We need to use the same marker everywhere. My CL to rename the
marker (CL 241661) and the CL to add more uses of the marker
under the old name (CL 241678) weren't coordinated with each other.
Fixes#52612
Change-Id: I97023c0769e518491924ef457fe03bf64a2cefa6
Reviewed-on: https://go-review.googlesource.com/c/go/+/403094
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"User" throws are throws due to some invariant broken by the application.
"System" throws are due to some invariant broken by the runtime,
environment, etc (i.e., not the fault of the application).
This CL sends "user" throws through the new fatal. Currently this
function is identical to throw, but with a different name to clearly
differentiate the throw type in the stack trace, and hopefully be a bit
more clear to users what it means.
This CL changes a few categories of throw to fatal:
1. Concurrent map read/write.
2. Deadlock detection.
3. Unlock of unlocked sync.Mutex.
4. Inconsistent results from syscall.AllThreadsSyscall.
"Thread exhaustion" and "out of memory" (usually address space full)
throws are additional throws that are arguably the fault of user code,
but I've left off for now because there is no specific invariant that
they have broken to get into these states.
For #51485
Change-Id: I713276a6c290fd34a6563e6e9ef378669d74ae32
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[This CL is part of a sequence implementing the proposal #51082.
The design doc is at https://go.dev/s/godocfmt-design.]
Run the updated gofmt, which reformats doc comments,
on the main repository. Vendored files are excluded.
For #51082.
Change-Id: I7332f099b60f716295fb34719c98c04eb1a85407
Reviewed-on: https://go-review.googlesource.com/c/go/+/384268
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
A future change to gofmt will rewrite
// Doc comment.
//go:foo
to
// Doc comment.
//
//go:foo
Apply that change preemptively to all comments (not necessarily just doc comments).
For #51082.
Change-Id: Iffe0285418d1e79d34526af3520b415a12203ca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/384260
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A future change to gofmt will rewrite
// Doc comment.
//
func f()
to
// Doc comment.
func f()
Apply that change preemptively to all doc comments.
For #51082.
Change-Id: I4023e16cfb0729b64a8590f071cd92f17343081d
Reviewed-on: https://go-review.googlesource.com/c/go/+/384259
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And then revert the bootstrap cmd directories and certain testdata.
And adjust tests as needed.
Not reverting the changes in std that are bootstrapped,
because some of those changes would appear in API docs,
and we want to use any consistently.
Instead, rewrite 'any' to 'interface{}' in cmd/dist for those directories
when preparing the bootstrap copy.
A few files changed as a result of running gofmt -w
not because of interface{} -> any but because they
hadn't been updated for the new //go:build lines.
Fixes#49884.
Change-Id: Ie8045cba995f65bd79c694ec77a1b3d1fe01bb09
Reviewed-on: https://go-review.googlesource.com/c/go/+/368254
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For #45435
Change-Id: I728accd9a53c1826243f52aa04dc2a0a1dfdaadf
Reviewed-on: https://go-review.googlesource.com/c/go/+/363672
Trust: Ian Lance Taylor <iant@golang.org>
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Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
This change clarifies that calling all Map methods inside the callback
of Range is allowed. For further assurance, a nested range call test
is also added.
Fixes#46399
Change-Id: I0a766a5c1470e6b573ec35df1ccd62b2e46f1561
Reviewed-on: https://go-review.googlesource.com/c/go/+/337389
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CL 344955 and CL 359476 removed almost all // +build lines, but leaving
some assembly files and generating scripts. Also, some files were added
with // +build lines after CL 359476 was merged. Remove these or rename
files where more appropriate.
For #41184
Change-Id: I7eb85a498ed9788b42a636e775f261d755504ffa
Reviewed-on: https://go-review.googlesource.com/c/go/+/361480
Trust: Tobias Klauser <tobias.klauser@gmail.com>
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TestHammerStoreLoad involves a stress test of StorePointer, which has a
write barrier. The "pointer" that is being written is not a real value,
which is generally fine (though not *really* safe) on 64-bit systems
because they never point to an actual object.
On 32-bit systems, however, this is much more likely. Because I can't
figure out how to rewrite the test such that it still is testing the
same conditions but is also using real pointers, just disable the GC
during the test, and make sure there isn't one currently in progress.
Fixes#49362.
Change-Id: If81883fedf06568132e6484f40c820aa69027a9c
Reviewed-on: https://go-review.googlesource.com/c/go/+/361455
Trust: Michael Knyszek <mknyszek@google.com>
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This benchmark simulates object starvation in order to force Ps to steal
objects from other Ps. Extracted from CL 314229.
Change-Id: Iee31df355ba04d80fbd91c4414e397a375e6d6d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/360256
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Use of these functions is almost (but not) always a bad idea.
Very rarely they are necessary, and third-party implementations
(using a mutex and an atomic word, say) cannot integrate as well
with the race detector as implmentations in package sync itself.
Fixes#45435.
Change-Id: I0128ca48ef5e0a3b09c913f0f3a7ee5c56388000
Reviewed-on: https://go-review.googlesource.com/c/go/+/319769
Trust: Russ Cox <rsc@golang.org>
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When these packages are released as part of Go 1.18,
Go 1.16 will no longer be supported, so we can remove
the +build tags in these files.
Ran go fix -fix=buildtag std cmd and then reverted the bootstrapDirs
as defined in src/cmd/dist/buildtool.go, which need to continue
to build with Go 1.4 for now.
Also reverted src/vendor and src/cmd/vendor, which will need
to be updated in their own repos first.
Manual changes in runtime/pprof/mprof_test.go to adjust line numbers.
For #41184.
Change-Id: Ic0f93f7091295b6abc76ed5cd6e6746e1280861e
Reviewed-on: https://go-review.googlesource.com/c/go/+/344955
Trust: Russ Cox <rsc@golang.org>
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Unlike what the comment says, the GC can see this pointer.
Might as well make it a real pointer, even though ^uintptr(0)
isn't currently causing problems.
Removed the comment about GC not seeing the pointer.
Change-Id: I04bc1fd4848698bec6afb79bd5fda671dfc9a073
Reviewed-on: https://go-review.googlesource.com/c/go/+/241661
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Colin Arnott <colin@urandom.co.uk>
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uint64 is guaranteed by the compiler to be aligned on 64-bit archs.
By using uint64+uint32 instead of [3]uint32 we can make use of the
guaranteed alignment to avoid the run-time alignment check.
On linux/amd64:
name old time/op new time/op delta
WaitGroupUncontended-4 8.84ns ± 3% 7.62ns ± 4% -13.72% (p=0.000 n=17+18)
WaitGroupAddDone-4 66.8ns ± 3% 45.9ns ± 2% -31.31% (p=0.000 n=20+18)
WaitGroupAddDoneWork-4 79.2ns ± 1% 56.6ns ± 1% -28.54% (p=0.000 n=17+20)
WaitGroupWait-4 2.83ns ± 2% 2.58ns ± 2% -9.05% (p=0.000 n=18+20)
WaitGroupWaitWork-4 16.8ns ± 6% 16.5ns ± 6% ~ (p=0.072 n=20+18)
WaitGroupActuallyWait-4 263ns ± 2% 261ns ± 5% ~ (p=0.063 n=18+20)
Change-Id: I314340f2ed8a47d8b9c15f8a3b07e41f252f4831
Reviewed-on: https://go-review.googlesource.com/c/go/+/189837
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
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