go/src/runtime/os_darwin.go, branch fix-runtime-test-GOMAXPROCS

runtime: gofmt after CL 643897 and CL 662455

2025-07-11T21:27:24Z

Change-Id: I3103325ebe29509c00b129a317b5708aece575a0 Reviewed-on: https://go-review.googlesource.com/c/go/+/687715 Reviewed-by: Michael Pratt Reviewed-by: Carlos Amedee LUCI-TryBot-Result: Go LUCI Auto-Submit: Tobias Klauser

runtime: rename ncpu to numCPUStartup

2025-05-19T19:47:30Z

ncpu is the total logical CPU count at startup. It is never updated. For #73193, we will start using updated CPU counts for updated GOMAXPROCS, making the ncpu name a bit ambiguous. Change to a less ambiguous name. While we're at it, give the OS specific lookup functions a common name, so it can be used outside of osinit later. For #73193. Change-Id: I6a6a636cf21cc60de36b211f3c374080849fc667 Reviewed-on: https://go-review.googlesource.com/c/go/+/672277 LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Knyszek Auto-Submit: Michael Pratt

runtime: cleanup M vgetrandom state before dropping P

2025-04-03T08:25:08Z

When an M is destroyed, we put its vgetrandom state back on the shared list for another M to reuse. This list is simply a slice, so appending to the slice may allocate. Currently this operation is performed in mdestroy, after the P is released, meaning allocation is not allowed. More the cleanup earlier in mdestroy when allocation is still OK. Also add //go:nowritebarrierrec to mdestroy since it runs without a P, which would have caught this bug. Fixes #73141. Change-Id: I6a6a636c3fbf5c6eec09d07a260e39dbb4d2db12 Reviewed-on: https://go-review.googlesource.com/c/go/+/662455 Reviewed-by: Jason Donenfeld LUCI-TryBot-Result: Go LUCI Reviewed-by: Keith Randall Reviewed-by: Keith Randall

runtime: use arc4random_buf() for readRandom

2024-10-07T15:34:53Z

readRandom doesn't matter on Linux because of startupRand, but it does on Windows and macOS. Windows already uses the same API as crypto/rand. Switch macOS away from the /dev/urandom read. Updates #68278 Cq-Include-Trybots: luci.golang.try:gotip-darwin-amd64_14 Change-Id: Ie8f105e35658a6f10ff68798d14883e3b212eb3e Reviewed-on: https://go-review.googlesource.com/c/go/+/608436 Reviewed-by: Roland Shoemaker Reviewed-by: Michael Knyszek LUCI-TryBot-Result: Go LUCI

cmd,log,net,runtime: simplify string prefix and suffix processing

2024-07-29T21:29:17Z

Use the TrimPrefix, TrimSuffix and CutPrefix to simplify the code. Change-Id: I3e2b271ec0d3f9ce664b830e2b0c21ab47337ed0 GitHub-Last-Rev: 4bd1577d2496173800d609da75b08f6de177aba9 GitHub-Pull-Request: golang/go#68629 Reviewed-on: https://go-review.googlesource.com/c/go/+/601675 LUCI-TryBot-Result: Go LUCI Auto-Submit: Ian Lance Taylor Reviewed-by: Michael Knyszek Reviewed-by: Ian Lance Taylor

math/rand, math/rand/v2: use ChaCha8 for global rand

2023-12-05T20:34:30Z

Move ChaCha8 code into internal/chacha8rand and use it to implement runtime.rand, which is used for the unseeded global source for both math/rand and math/rand/v2. This also affects the calculation of the start point for iteration over very very large maps (when the 32-bit fastrand is not big enough). The benefit is that misuse of the global random number generators in math/rand and math/rand/v2 in contexts where non-predictable randomness is important for security reasons is no longer a security problem, removing a common mistake among programmers who are unaware of the different kinds of randomness. The cost is an extra 304 bytes per thread stored in the m struct plus 2-3ns more per random uint64 due to the more sophisticated algorithm. Using PCG looks like it would cost about the same, although I haven't benchmarked that. Before this, the math/rand and math/rand/v2 global generator was wyrand (https://github.com/wangyi-fudan/wyhash). For math/rand, using wyrand instead of the Mitchell/Reeds/Thompson ALFG was justifiable, since the latter was not any better. But for math/rand/v2, the global generator really should be at least as good as one of the well-studied, specific algorithms provided directly by the package, and it's not. (Wyrand is still reasonable for scheduling and cache decisions.) Good randomness does have a cost: about twice wyrand. Also rationalize the various runtime rand references. goos: linux goarch: amd64 pkg: math/rand/v2 cpu: AMD Ryzen 9 7950X 16-Core Processor │ bbb48afeb7.amd64 │ 5cf807d1ea.amd64 │ │ sec/op │ sec/op vs base │ ChaCha8-32 1.862n ± 2% 1.861n ± 2% ~ (p=0.825 n=20) PCG_DXSM-32 1.471n ± 1% 1.460n ± 2% ~ (p=0.153 n=20) SourceUint64-32 1.636n ± 2% 1.582n ± 1% -3.30% (p=0.000 n=20) GlobalInt64-32 2.087n ± 1% 3.663n ± 1% +75.54% (p=0.000 n=20) GlobalInt64Parallel-32 0.1042n ± 1% 0.2026n ± 1% +94.48% (p=0.000 n=20) GlobalUint64-32 2.263n ± 2% 3.724n ± 1% +64.57% (p=0.000 n=20) GlobalUint64Parallel-32 0.1019n ± 1% 0.1973n ± 1% +93.67% (p=0.000 n=20) Int64-32 1.771n ± 1% 1.774n ± 1% ~ (p=0.449 n=20) Uint64-32 1.863n ± 2% 1.866n ± 1% ~ (p=0.364 n=20) GlobalIntN1000-32 3.134n ± 3% 4.730n ± 2% +50.95% (p=0.000 n=20) IntN1000-32 2.489n ± 1% 2.489n ± 1% ~ (p=0.683 n=20) Int64N1000-32 2.521n ± 1% 2.516n ± 1% ~ (p=0.394 n=20) Int64N1e8-32 2.479n ± 1% 2.478n ± 2% ~ (p=0.743 n=20) Int64N1e9-32 2.530n ± 2% 2.514n ± 2% ~ (p=0.193 n=20) Int64N2e9-32 2.501n ± 1% 2.494n ± 1% ~ (p=0.616 n=20) Int64N1e18-32 3.227n ± 1% 3.205n ± 1% ~ (p=0.101 n=20) Int64N2e18-32 3.647n ± 1% 3.599n ± 1% ~ (p=0.019 n=20) Int64N4e18-32 5.135n ± 1% 5.069n ± 2% ~ (p=0.034 n=20) Int32N1000-32 2.657n ± 1% 2.637n ± 1% ~ (p=0.180 n=20) Int32N1e8-32 2.636n ± 1% 2.636n ± 1% ~ (p=0.763 n=20) Int32N1e9-32 2.660n ± 2% 2.638n ± 1% ~ (p=0.358 n=20) Int32N2e9-32 2.662n ± 2% 2.618n ± 2% ~ (p=0.064 n=20) Float32-32 2.272n ± 2% 2.239n ± 2% ~ (p=0.194 n=20) Float64-32 2.272n ± 1% 2.286n ± 2% ~ (p=0.763 n=20) ExpFloat64-32 3.762n ± 1% 3.744n ± 1% ~ (p=0.171 n=20) NormFloat64-32 3.706n ± 1% 3.655n ± 2% ~ (p=0.066 n=20) Perm3-32 32.93n ± 3% 34.62n ± 1% +5.13% (p=0.000 n=20) Perm30-32 202.9n ± 1% 204.0n ± 1% ~ (p=0.482 n=20) Perm30ViaShuffle-32 115.0n ± 1% 114.9n ± 1% ~ (p=0.358 n=20) ShuffleOverhead-32 112.8n ± 1% 112.7n ± 1% ~ (p=0.692 n=20) Concurrent-32 2.107n ± 0% 3.725n ± 1% +76.75% (p=0.000 n=20) goos: darwin goarch: arm64 pkg: math/rand/v2 │ bbb48afeb7.arm64 │ 5cf807d1ea.arm64 │ │ sec/op │ sec/op vs base │ ChaCha8-8 2.480n ± 0% 2.429n ± 0% -2.04% (p=0.000 n=20) PCG_DXSM-8 2.531n ± 0% 2.530n ± 0% ~ (p=0.877 n=20) SourceUint64-8 2.534n ± 0% 2.533n ± 0% ~ (p=0.732 n=20) GlobalInt64-8 2.172n ± 1% 4.794n ± 0% +120.67% (p=0.000 n=20) GlobalInt64Parallel-8 0.4320n ± 0% 0.9605n ± 0% +122.32% (p=0.000 n=20) GlobalUint64-8 2.182n ± 0% 4.770n ± 0% +118.58% (p=0.000 n=20) GlobalUint64Parallel-8 0.4307n ± 0% 0.9583n ± 0% +122.51% (p=0.000 n=20) Int64-8 4.107n ± 0% 4.104n ± 0% ~ (p=0.416 n=20) Uint64-8 4.080n ± 0% 4.080n ± 0% ~ (p=0.052 n=20) GlobalIntN1000-8 2.814n ± 2% 5.643n ± 0% +100.50% (p=0.000 n=20) IntN1000-8 4.141n ± 0% 4.139n ± 0% ~ (p=0.140 n=20) Int64N1000-8 4.140n ± 0% 4.140n ± 0% ~ (p=0.313 n=20) Int64N1e8-8 4.140n ± 0% 4.139n ± 0% ~ (p=0.103 n=20) Int64N1e9-8 4.139n ± 0% 4.140n ± 0% ~ (p=0.761 n=20) Int64N2e9-8 4.140n ± 0% 4.140n ± 0% ~ (p=0.636 n=20) Int64N1e18-8 5.266n ± 0% 5.326n ± 1% +1.14% (p=0.001 n=20) Int64N2e18-8 6.052n ± 0% 6.167n ± 0% +1.90% (p=0.000 n=20) Int64N4e18-8 8.826n ± 0% 9.051n ± 0% +2.55% (p=0.000 n=20) Int32N1000-8 4.127n ± 0% 4.132n ± 0% +0.12% (p=0.000 n=20) Int32N1e8-8 4.126n ± 0% 4.131n ± 0% +0.12% (p=0.000 n=20) Int32N1e9-8 4.127n ± 0% 4.132n ± 0% +0.12% (p=0.000 n=20) Int32N2e9-8 4.132n ± 0% 4.131n ± 0% ~ (p=0.017 n=20) Float32-8 4.109n ± 0% 4.105n ± 0% ~ (p=0.379 n=20) Float64-8 4.107n ± 0% 4.106n ± 0% ~ (p=0.867 n=20) ExpFloat64-8 5.339n ± 0% 5.383n ± 0% +0.82% (p=0.000 n=20) NormFloat64-8 5.735n ± 0% 5.737n ± 1% ~ (p=0.856 n=20) Perm3-8 26.65n ± 0% 26.80n ± 1% +0.58% (p=0.000 n=20) Perm30-8 194.8n ± 1% 197.0n ± 0% +1.18% (p=0.000 n=20) Perm30ViaShuffle-8 156.6n ± 0% 157.6n ± 1% +0.61% (p=0.000 n=20) ShuffleOverhead-8 124.9n ± 0% 125.5n ± 0% +0.52% (p=0.000 n=20) Concurrent-8 2.434n ± 3% 5.066n ± 0% +108.09% (p=0.000 n=20) goos: linux goarch: 386 pkg: math/rand/v2 cpu: AMD Ryzen 9 7950X 16-Core Processor │ bbb48afeb7.386 │ 5cf807d1ea.386 │ │ sec/op │ sec/op vs base │ ChaCha8-32 11.295n ± 1% 4.748n ± 2% -57.96% (p=0.000 n=20) PCG_DXSM-32 7.693n ± 1% 7.738n ± 2% ~ (p=0.542 n=20) SourceUint64-32 7.658n ± 2% 7.622n ± 2% ~ (p=0.344 n=20) GlobalInt64-32 3.473n ± 2% 7.526n ± 2% +116.73% (p=0.000 n=20) GlobalInt64Parallel-32 0.3198n ± 0% 0.5444n ± 0% +70.22% (p=0.000 n=20) GlobalUint64-32 3.612n ± 0% 7.575n ± 1% +109.69% (p=0.000 n=20) GlobalUint64Parallel-32 0.3168n ± 0% 0.5403n ± 0% +70.51% (p=0.000 n=20) Int64-32 7.673n ± 2% 7.789n ± 1% ~ (p=0.122 n=20) Uint64-32 7.773n ± 1% 7.827n ± 2% ~ (p=0.920 n=20) GlobalIntN1000-32 6.268n ± 1% 9.581n ± 1% +52.87% (p=0.000 n=20) IntN1000-32 10.33n ± 2% 10.45n ± 1% ~ (p=0.233 n=20) Int64N1000-32 10.98n ± 2% 11.01n ± 1% ~ (p=0.401 n=20) Int64N1e8-32 11.19n ± 2% 10.97n ± 1% ~ (p=0.033 n=20) Int64N1e9-32 11.06n ± 1% 11.08n ± 1% ~ (p=0.498 n=20) Int64N2e9-32 11.10n ± 1% 11.01n ± 2% ~ (p=0.995 n=20) Int64N1e18-32 15.23n ± 2% 15.04n ± 1% ~ (p=0.973 n=20) Int64N2e18-32 15.89n ± 1% 15.85n ± 1% ~ (p=0.409 n=20) Int64N4e18-32 18.96n ± 2% 19.34n ± 2% ~ (p=0.048 n=20) Int32N1000-32 10.46n ± 2% 10.44n ± 2% ~ (p=0.480 n=20) Int32N1e8-32 10.46n ± 2% 10.49n ± 2% ~ (p=0.951 n=20) Int32N1e9-32 10.28n ± 2% 10.26n ± 1% ~ (p=0.431 n=20) Int32N2e9-32 10.50n ± 2% 10.44n ± 2% ~ (p=0.249 n=20) Float32-32 13.80n ± 2% 13.80n ± 2% ~ (p=0.751 n=20) Float64-32 23.55n ± 2% 23.87n ± 0% ~ (p=0.408 n=20) ExpFloat64-32 15.36n ± 1% 15.29n ± 2% ~ (p=0.316 n=20) NormFloat64-32 13.57n ± 1% 13.79n ± 1% +1.66% (p=0.005 n=20) Perm3-32 45.70n ± 2% 46.99n ± 2% +2.81% (p=0.001 n=20) Perm30-32 399.0n ± 1% 403.8n ± 1% +1.19% (p=0.006 n=20) Perm30ViaShuffle-32 349.0n ± 1% 350.4n ± 1% ~ (p=0.909 n=20) ShuffleOverhead-32 322.3n ± 1% 323.8n ± 1% ~ (p=0.410 n=20) Concurrent-32 3.331n ± 1% 7.312n ± 1% +119.50% (p=0.000 n=20) For #61716. Change-Id: Ibdddeed85c34d9ae397289dc899e04d4845f9ed2 Reviewed-on: https://go-review.googlesource.com/c/go/+/516860 Reviewed-by: Michael Pratt Reviewed-by: Filippo Valsorda LUCI-TryBot-Result: Go LUCI

runtime: clear procid in unminit

2023-09-06T18:36:02Z

Extra Ms can move between system threads. needm will reinitialize procid (via minit) on the new thread, but leaving a stale procid behind after dropm can be misleading if printing the M early in needm for debugging. Change-Id: I668891971a0baeab31170d1e40a97126416e7379 Reviewed-on: https://go-review.googlesource.com/c/go/+/526118 Reviewed-by: Cherry Mui Auto-Submit: Michael Pratt Reviewed-by: Michael Knyszek LUCI-TryBot-Result: Go LUCI

runtime: guard against runtime/sema* ops on Darwin signal stack.

2023-08-16T17:51:47Z

These operations misbehave and cause hangs and flakes. Fail hard if they are attempted. Tested by backing out the Darwin-profiling-hang fix CL 518836 and running run.bash, the guard panicked in runtime/pprof tests, as expected/hoped. Updates #61768 Change-Id: I89b6f85745fbaa2245141ea98f584afc5d6b133e Reviewed-on: https://go-review.googlesource.com/c/go/+/519275 Reviewed-by: Austin Clements Run-TryBot: David Chase TryBot-Result: Gopher Robot

runtime: profiling on Darwin cannot use blocking reads

2023-08-14T15:41:38Z

On Darwin (and assume also on iOS but not sure), notetsleepg cannot be called in a signal-handling context. Avoid this by disabling block reads on Darwin. An alternate approach was to add "sigNote" with a pipe-based implementation on Darwin, but that ultimately would have required at least one more linkname between runtime and syscall to avoid racing with fork and opening the pipe, so, not. Fixes #61768. Change-Id: I0e8dd4abf9a606a3ff73fc37c3bd75f55924e07e Reviewed-on: https://go-review.googlesource.com/c/go/+/518836 Run-TryBot: David Chase TryBot-Result: Gopher Robot Reviewed-by: Michael Knyszek

cmd/link, runtime: Apple libc atfork workaround take 3

2023-01-10T20:34:22Z

CL 451735 worked around bugs in Apple's atfork handlers by calling notify_is_valid_token and xpc_atfork_child at startup, so that init code that wouldn't be safe in the child process would be warmed up in the parent process instead, but xpc_atfork_child broke use of the xpc library in Go programs, and xpc is internally used by various macOS frameworks (#57263). CL 459175 reverted that change, and then CL 459176 tried a new approach: use __fork, which doesn't call any of the atfork handlers at all. That worked, but an Apple engineer reviewing the change in private email suggests that since __fork is not public API, it should be avoided. The same engineer (with access to the source code for the xpc library) suggests that the breakage in #57263 is caused by xpc_atfork_child marking the library as unusable, expecting an imminent call to exec, and that calling xpc_date_create_from_current instead would do the necessary initialization without marking xpc as unusable. CL 460475 reverted that change, to prepare for this one. This CL goes back to the original “call functions to warm things up” approach, replacing xpc_atfork_child with xpc_date_create_from_current. The CL also updates cmd/link to use OS and SDK version 10.13.0 for x86 macOS binaries, up from 10.9.0, also suggested by the Apple engineer. Combined with the two warmup calls, this makes the fork hangs go away. The minimum macOS version has been 10.13 High Sierra since Go 1.17, so there should be no problem with writing that in the binaries too. Fixes #33565. Fixes #56784. Fixes #57263. Fixes #57577. Change-Id: I20769d9daa1fe9ea930f8009481335f8a14dc21b Reviewed-on: https://go-review.googlesource.com/c/go/+/460476 Auto-Submit: Russ Cox Run-TryBot: Russ Cox TryBot-Result: Gopher Robot Reviewed-by: Bryan Mills Reviewed-by: Cherry Mui