Fix run command race (#1470)

* Use exec.CommandContext to simplfy timeout handling

And fixing the data races which can be identified by the added tests when -race enabled.

* Use sleep commmand instead of reading from stdin

* Make the error handling go-esque

modules/process/manager.go

@@ -6,13 +6,12 @@ package process
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"os/exec"
 	"sync"
 	"time"
-
-	"code.gitea.io/gitea/modules/log"
 )
 
 // TODO: This packages still uses a singleton for the Manager.
@@ -101,7 +100,10 @@ func (pm *Manager) ExecDirEnv(timeout time.Duration, dir, desc string, env []str
 	stdOut := new(bytes.Buffer)
 	stdErr := new(bytes.Buffer)
 
-	cmd := exec.Command(cmdName, args...)
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, cmdName, args...)
 	cmd.Dir = dir
 	cmd.Env = env
 	cmd.Stdout = stdOut
@@ -111,30 +113,14 @@ func (pm *Manager) ExecDirEnv(timeout time.Duration, dir, desc string, env []str
 	}
 
 	pid := pm.Add(desc, cmd)
-	done := make(chan error)
+	err := cmd.Wait()
-	go func() {
-		done <- cmd.Wait()
-	}()
-
-	var err error
-	select {
-	case <-time.After(timeout):
-		if errKill := pm.Kill(pid); errKill != nil {
-			log.Error(4, "exec(%d:%s) failed to kill: %v", pid, desc, errKill)
-		}
-		<-done
-		return "", "", ErrExecTimeout
-	case err = <-done:
-	}
-
 	pm.Remove(pid)
 
 	if err != nil {
-		out := fmt.Errorf("exec(%d:%s) failed: %v stdout: %v stderr: %v", pid, desc, err, stdOut, stdErr)
+		err = fmt.Errorf("exec(%d:%s) failed: %v(%v) stdout: %v stderr: %v", pid, desc, err, ctx.Err(), stdOut, stdErr)
-		return stdOut.String(), stdErr.String(), out
 	}
 
-	return stdOut.String(), stdErr.String(), nil
+	return stdOut.String(), stdErr.String(), err
 }
 
 // Kill and remove a process from list.

modules/process/manager_test.go

@@ -3,6 +3,7 @@ package process
 import (
 	"os/exec"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -31,3 +32,27 @@ func TestManager_Remove(t *testing.T) {
 	_, exists := pm.Processes[pid2]
 	assert.False(t, exists, "PID %d is in the list but shouldn't", pid2)
 }
+
+func TestExecTimeoutNever(t *testing.T) {
+
+	// TODO Investigate how to improve the time elapsed per round.
+	maxLoops := 10
+	for i := 1; i < maxLoops; i++ {
+		_, stderr, err := GetManager().ExecTimeout(5*time.Second, "ExecTimeout", "git", "--version")
+		if err != nil {
+			t.Fatalf("git --version: %v(%s)", err, stderr)
+		}
+	}
+}
+
+func TestExecTimeoutAlways(t *testing.T) {
+
+	maxLoops := 100
+	for i := 1; i < maxLoops; i++ {
+		_, stderr, err := GetManager().ExecTimeout(100*time.Microsecond, "ExecTimeout", "sleep", "5")
+		// TODO Simplify logging and errors to get precise error type. E.g. checking "if err != context.DeadlineExceeded".
+		if err == nil {
+			t.Fatalf("sleep 5 secs: %v(%s)", err, stderr)
+		}
+	}
+}