libcamera: process: Use pid_ member to decide if running

Instead of using a separate member variable, use `pid_ > 0` to determine
if the process is still running. Previously the value of `pid_` was not
reset to -1 when the process terminated, but since it is only meaningful
while the process is running, reset it to -1 in `Process::died()`.

Neither `pid_` nor `running_` are exposed, so this change has no effect
on the public interface or observable behaviour.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/process.cpp

@@ -208,7 +208,7 @@ const struct sigaction &ProcessManager::oldsa() const
  */
 
 Process::Process()
-	: pid_(-1), running_(false), exitStatus_(NotExited), exitCode_(0)
+	: pid_(-1), exitStatus_(NotExited), exitCode_(0)
 {
 }
 
@@ -240,7 +240,7 @@ int Process::start(const std::string &path,
 {
 	int ret;
 
-	if (running_)
+	if (pid_ > 0)
 		return -EBUSY;
 
 	for (int fd : fds) {
@@ -257,8 +257,6 @@ int Process::start(const std::string &path,
 		pid_ = childPid;
 		ProcessManager::instance()->registerProcess(this);
 
-		running_ = true;
-
 		return 0;
 	} else {
 		if (isolate())
@@ -348,7 +346,7 @@ int Process::isolate()
  */
 void Process::died(int wstatus)
 {
-	running_ = false;
+	pid_ = -1;
 	exitStatus_ = WIFEXITED(wstatus) ? NormalExit : SignalExit;
 	exitCode_ = exitStatus_ == NormalExit ? WEXITSTATUS(wstatus) : -1;