Commit 7f31971f authored by Joe Tsai's avatar Joe Tsai Committed by Joe Tsai

testing: synchronize writes to the root's Writer

Prior to this change it was possible to see interleaved messages:
<<<
=== RUN   Test/LongLongLongLongName48
=== RUN   Test/LongLon=== RUN   Test/LongLongLongLongName50
gLongLongName49
=== RUN   Test/LongLongLongLongName51
>
> This change fixes it such that you see:
> <<<
> === RUN   Test/LongLongLongLongName48
> === RUN   Test/LongLongLongLongName49
> === RUN   Test/LongLongLongLongName50
> === RUN   Test/LongLongLongLongName51

Fixes #18741

Change-Id: I2529d724065dc65b3e9eb3d7cbeeda82a2d0cfd4
Reviewed-on: https://go-review.googlesource.com/35556Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
parent 048b8cec
......@@ -8,7 +8,9 @@ import (
"bytes"
"fmt"
"regexp"
"runtime"
"strings"
"sync"
"sync/atomic"
"time"
)
......@@ -532,3 +534,44 @@ func TestParallelSub(t *T) {
<-c
}
}
type funcWriter func([]byte) (int, error)
func (fw funcWriter) Write(b []byte) (int, error) { return fw(b) }
func TestRacyOutput(t *T) {
var runs int32 // The number of running Writes
var races int32 // Incremented for each race detected
raceDetector := func(b []byte) (int, error) {
// Check if some other goroutine is concurrently calling Write.
if atomic.LoadInt32(&runs) > 0 {
atomic.AddInt32(&races, 1) // Race detected!
}
atomic.AddInt32(&runs, 1)
defer atomic.AddInt32(&runs, -1)
runtime.Gosched() // Increase probability of a race
return len(b), nil
}
var wg sync.WaitGroup
root := &T{
common: common{w: funcWriter(raceDetector), chatty: true},
context: newTestContext(1, newMatcher(regexp.MatchString, "", "")),
}
root.Run("", func(t *T) {
for i := 0; i < 100; i++ {
wg.Add(1)
go func(i int) {
defer wg.Done()
t.Run(fmt.Sprint(i), func(t *T) {
t.Logf("testing run %d", i)
})
}(i)
}
})
wg.Wait()
if races > 0 {
t.Errorf("detected %d racy Writes", races)
}
}
......@@ -259,7 +259,7 @@ var (
// common holds the elements common between T and B and
// captures common methods such as Errorf.
type common struct {
mu sync.RWMutex // guards output, failed, and done.
mu sync.RWMutex // guards output, w, failed, and done.
output []byte // Output generated by test or benchmark.
w io.Writer // For flushToParent.
chatty bool // A copy of the chatty flag.
......@@ -687,7 +687,9 @@ func (t *T) Run(name string, f func(t *T)) bool {
root := t.parent
for ; root.parent != nil; root = root.parent {
}
root.mu.Lock()
fmt.Fprintf(root.w, "=== RUN %s\n", t.name)
root.mu.Unlock()
}
// Instead of reducing the running count of this test before calling the
// tRunner and increasing it afterwards, we rely on tRunner keeping the
......
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