| // Copyright 2023 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Tests to make sure the runtime doesn't generate futile wakeups. For example, |
| // it makes sure that a block on a channel send that unblocks briefly only to |
| // immediately go back to sleep (in such a way that doesn't reveal any useful |
| // information, and is purely an artifact of the runtime implementation) doesn't |
| // make it into the trace. |
| |
| //go:build ignore |
| |
| package main |
| |
| import ( |
| "context" |
| "log" |
| "os" |
| "runtime" |
| "runtime/trace" |
| "sync" |
| ) |
| |
| func main() { |
| if err := trace.Start(os.Stdout); err != nil { |
| log.Fatalf("failed to start tracing: %v", err) |
| } |
| |
| defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(8)) |
| c0 := make(chan int, 1) |
| c1 := make(chan int, 1) |
| c2 := make(chan int, 1) |
| const procs = 2 |
| var done sync.WaitGroup |
| done.Add(4 * procs) |
| for p := 0; p < procs; p++ { |
| const iters = 1e3 |
| go func() { |
| trace.WithRegion(context.Background(), "special", func() { |
| for i := 0; i < iters; i++ { |
| runtime.Gosched() |
| c0 <- 0 |
| } |
| done.Done() |
| }) |
| }() |
| go func() { |
| trace.WithRegion(context.Background(), "special", func() { |
| for i := 0; i < iters; i++ { |
| runtime.Gosched() |
| <-c0 |
| } |
| done.Done() |
| }) |
| }() |
| go func() { |
| trace.WithRegion(context.Background(), "special", func() { |
| for i := 0; i < iters; i++ { |
| runtime.Gosched() |
| select { |
| case c1 <- 0: |
| case c2 <- 0: |
| } |
| } |
| done.Done() |
| }) |
| }() |
| go func() { |
| trace.WithRegion(context.Background(), "special", func() { |
| for i := 0; i < iters; i++ { |
| runtime.Gosched() |
| select { |
| case <-c1: |
| case <-c2: |
| } |
| } |
| done.Done() |
| }) |
| }() |
| } |
| done.Wait() |
| |
| trace.Stop() |
| } |