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// Copyright 2018 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.
//go:build !plan9 && !windows && !js
package runtime_test
import (
"io"
"os/exec"
"syscall"
"testing"
"time"
)
// Issue #27250. Spurious wakeups to pthread_cond_timedwait_relative_np
// shouldn't cause semasleep to retry with the same timeout which would
// cause indefinite spinning.
func TestSpuriousWakeupsNeverHangSemasleep(t *testing.T) {
if *flagQuick {
t.Skip("-quick")
}
t.Parallel() // Waits for a program to sleep for 1s.
exe, err := buildTestProg(t, "testprog")
if err != nil {
t.Fatal(err)
}
cmd := exec.Command(exe, "After1")
stdout, err := cmd.StdoutPipe()
if err != nil {
t.Fatalf("StdoutPipe: %v", err)
}
beforeStart := time.Now()
if err := cmd.Start(); err != nil {
t.Fatalf("Failed to start command: %v", err)
}
doneCh := make(chan error, 1)
go func() {
doneCh <- cmd.Wait()
close(doneCh)
}()
t.Cleanup(func() {
cmd.Process.Kill()
<-doneCh
})
// Wait for After1 to close its stdout so that we know the runtime's SIGIO
// handler is registered.
b, err := io.ReadAll(stdout)
if len(b) > 0 {
t.Logf("read from testprog stdout: %s", b)
}
if err != nil {
t.Fatalf("error reading from testprog: %v", err)
}
// Wait for an arbitrary timeout longer than one second. The subprocess itself
// attempts to sleep for one second, but if the machine running the test is
// heavily loaded that subprocess may not schedule very quickly even if the
// bug remains fixed. (This is fine, because if the bug really is unfixed we
// can keep the process hung indefinitely, as long as we signal it often
// enough.)
timeout := 10 * time.Second
// The subprocess begins sleeping for 1s after it writes to stdout, so measure
// the timeout from here (not from when we started creating the process).
// That should reduce noise from process startup overhead.
ready := time.Now()
// With the repro running, we can continuously send to it
// a signal that the runtime considers non-terminal,
// such as SIGIO, to spuriously wake up
// pthread_cond_timedwait_relative_np.
ticker := time.NewTicker(200 * time.Millisecond)
defer ticker.Stop()
for {
select {
case now := <-ticker.C:
if now.Sub(ready) > timeout {
t.Error("Program failed to return on time and has to be killed, issue #27520 still exists")
// Send SIGQUIT to get a goroutine dump.
// Stop sending SIGIO so that the program can clean up and actually terminate.
cmd.Process.Signal(syscall.SIGQUIT)
return
}
// Send the pesky signal that toggles spinning
// indefinitely if #27520 is not fixed.
cmd.Process.Signal(syscall.SIGIO)
case err := <-doneCh:
if err != nil {
t.Fatalf("The program returned but unfortunately with an error: %v", err)
}
if time.Since(beforeStart) < 1*time.Second {
// The program was supposed to sleep for a full (monotonic) second;
// it should not return before that has elapsed.
t.Fatalf("The program stopped too quickly.")
}
return
}
}
}
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