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dcrdtest: avoid concurrent exec.Cmd.Wait calls #22

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Apr 4, 2024
Merged

dcrdtest: avoid concurrent exec.Cmd.Wait calls #22

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52 changes: 34 additions & 18 deletions dcrdtest/node.go
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Original file line number Diff line number Diff line change
Expand Up @@ -177,12 +177,15 @@ func (n *nodeConfig) String() string {
type node struct {
config *nodeConfig

cmd *exec.Cmd
pidFile string
stderr io.ReadCloser
stdout io.ReadCloser
wg sync.WaitGroup
pid int
cmd *exec.Cmd
cmdStarted chan struct{} // Closed after cmd is started and assigned
cmdDone chan error // Sent error and closed after cmdErr is assigned
cmdErr error // Must only be read after receiving on cmdDone
pidFile string
stderr io.ReadCloser
stdout io.ReadCloser
wg sync.WaitGroup
pid int

// Locally bound addresses for the subsystems.
p2pAddr string
Expand All @@ -202,8 +205,10 @@ func (n *node) logf(format string, args ...interface{}) {
// as the base for the log and data directories for dcrd.
func newNode(config *nodeConfig, dataDir string) (*node, error) {
return &node{
config: config,
dataDir: dataDir,
config: config,
dataDir: dataDir,
cmdStarted: make(chan struct{}),
cmdDone: make(chan error, 1),
}, nil
}

Expand Down Expand Up @@ -309,6 +314,7 @@ func (n *node) start(ctx context.Context) error {
return fmt.Errorf("%w: %v", errDcrdCmdExec, err)
}
n.cmd = cmd
close(n.cmdStarted)
n.pid = n.cmd.Process.Pid

// Unblock pipes now that pid is available.
Expand All @@ -330,17 +336,21 @@ func (n *node) start(ctx context.Context) error {
return err
}

earlyShutdown := make(chan error, 1)
n.wg.Add(1)
go func() {
earlyShutdown <- cmd.Wait()
defer n.wg.Done()

n.cmdErr = n.cmd.Wait()
n.cmdDone <- n.cmdErr
close(n.cmdDone)
}()

// Read the RPC and P2P addresses.
select {
case <-ctx.Done():
_ = n.stop() // Cleanup what has been done so far.
return ctx.Err()
case err := <-earlyShutdown:
case err := <-n.cmdDone:
_ = n.stop()
return err
case <-gotSubsysAddrs:
Expand All @@ -358,12 +368,20 @@ func (n *node) stop() error {
log.Tracef("stop %p", n.cmd)
defer log.Tracef("stop done")

if n.cmd == nil || n.cmd.Process == nil {
// return if not properly initialized
// or error starting the process
select {
case <-n.cmdStarted:
default:
// has not been started (yet, or ever)
return nil
}

select {
case <-n.cmdDone:
// already stopped
return nil
default:
}

// Attempt a graceful dcrd shutdown by closing the pipeRX files.
err := n.config.pipeRX.close()
if err != nil {
Expand All @@ -389,8 +407,8 @@ func (n *node) stop() error {

// Wait for command to exit.
log.Tracef("stop cmd.Wait")
err = n.cmd.Wait()
if err != nil {
<-n.cmdDone
if err := n.cmdErr; err != nil {
log.Debugf("stop cmd.Wait error: %v", err)
}

Expand All @@ -399,8 +417,6 @@ func (n *node) stop() error {
n.logf("Unable to close pipe TX: %v", err)
}

// Mark command terminated.
n.cmd = nil
return nil
}

Expand Down
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