From 087582a964ae4832d4cf6d4ff260cb8739a0e96f Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Mon, 5 Nov 2012 17:01:43 +0100
Subject: [PATCH] Linux: Synchronize thread startup

The thread ID reported to core was not always initialized prior the RPC
call. The 'startup_lock' ensures that the thread is completely
initialized before this information gets propagated.
---
 base-linux/src/base/thread/thread_linux.cc | 29 ++++++++++++++++++----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/base-linux/src/base/thread/thread_linux.cc b/base-linux/src/base/thread/thread_linux.cc
index 5625c3b5f9..7f72dd1212 100644
--- a/base-linux/src/base/thread/thread_linux.cc
+++ b/base-linux/src/base/thread/thread_linux.cc
@@ -27,13 +27,20 @@ using namespace Genode;
 static void empty_signal_handler(int) { }
 
 
+static Lock &startup_lock()
+{
+	static Lock lock(Lock::LOCKED);
+	return lock;
+}
+
+
 /**
  * Signal handler for killing the thread
  */
 static void thread_exit_signal_handler(int) { lx_exit(0); }
 
 
-static void thread_start(void *)
+static void thread_start(void *arg)
 {
 	/*
 	 * Set signal handler such that canceled system calls get not
@@ -46,6 +53,16 @@ static void thread_start(void *)
 	 */
 	lx_sigaction(LX_SIGCHLD, (void (*)(int))1);
 
+	Thread_base *thread = (Thread_base *)arg;
+
+	/* inform core about the new thread and process ID of the new thread */
+	Linux_cpu_session *cpu = dynamic_cast<Linux_cpu_session *>(env()->cpu_session());
+	if (cpu)
+		cpu->thread_id(thread->cap(), thread->tid().pid, thread->tid().tid);
+
+	/* wakeup 'start' function */
+	startup_lock().unlock();
+
 	Thread_base::myself()->entry();
 	sleep_forever();
 }
@@ -90,6 +107,10 @@ void Thread_base::_deinit_platform_thread()
 
 void Thread_base::start()
 {
+	/* synchronize calls of the 'start' function */
+	static Lock lock;
+	Lock::Guard guard(lock);
+
 	/*
 	 * The first time we enter this code path, the 'start' function is
 	 * called by the main thread as there cannot exist other threads
@@ -107,10 +128,8 @@ void Thread_base::start()
 	_tid.tid = lx_create_thread(thread_start, thread_sp, this);
 	_tid.pid = lx_getpid();
 
-	/* inform core about the new thread and process ID of the new thread */
-	Linux_cpu_session *cpu = dynamic_cast<Linux_cpu_session *>(env()->cpu_session());
-	if (cpu)
-		cpu->thread_id(_thread_cap, _tid.pid, _tid.tid);
+	/* wait until the 'thread_start' function got entered */
+	startup_lock().lock();
 }