From be3d5232c83d74c862bb34ed45caea677fa3b214 Mon Sep 17 00:00:00 2001
From: Martin Stein <martin.stein@genode-labs.com>
Date: Thu, 8 Jul 2021 01:32:13 +0200
Subject: [PATCH] base-hw: kernel-data lock as Main member

Let the global kernel-data lock be a member of the one Kernel::Main object
instead of having it as global static variable.

Ref #4217
---
 repos/base-hw/src/core/kernel/lock.cc         | 10 +----
 repos/base-hw/src/core/kernel/lock.h          |  8 ++--
 repos/base-hw/src/core/kernel/main.cc         | 44 ++++++++++---------
 .../base-hw/src/core/spec/arm/kernel/lock.cc  | 11 +----
 4 files changed, 31 insertions(+), 42 deletions(-)

diff --git a/repos/base-hw/src/core/kernel/lock.cc b/repos/base-hw/src/core/kernel/lock.cc
index 00a85a6582..21ed98b44d 100644
--- a/repos/base-hw/src/core/kernel/lock.cc
+++ b/repos/base-hw/src/core/kernel/lock.cc
@@ -11,19 +11,13 @@
  * under the terms of the GNU Affero General Public License version 3.
  */
 
-#include <base/lock_guard.h>
+/* Genode includes */
 #include <cpu/atomic.h>
 #include <cpu/memory_barrier.h>
 
+/* base-hw Core includes */
 #include <kernel/cpu.h>
 #include <kernel/lock.h>
-#include <kernel/kernel.h>
-
-Kernel::Lock & Kernel::data_lock()
-{
-	static Kernel::Lock lock;
-	return lock;
-}
 
 
 void Kernel::Lock::lock()
diff --git a/repos/base-hw/src/core/kernel/lock.h b/repos/base-hw/src/core/kernel/lock.h
index 6c7c5c9fb6..1befd37bac 100644
--- a/repos/base-hw/src/core/kernel/lock.h
+++ b/repos/base-hw/src/core/kernel/lock.h
@@ -15,12 +15,10 @@
 #ifndef _CORE__SPEC__SMP__KERNEL__LOCK_H_
 #define _CORE__SPEC__SMP__KERNEL__LOCK_H_
 
-namespace Kernel {
+/* Genode includes */
+#include <base/lock_guard.h>
 
-	class Lock;
-
-	Lock & data_lock();
-}
+namespace Kernel { class Lock; }
 
 
 class Kernel::Lock
diff --git a/repos/base-hw/src/core/kernel/main.cc b/repos/base-hw/src/core/kernel/main.cc
index 253e066e9f..99f3e7d66c 100644
--- a/repos/base-hw/src/core/kernel/main.cc
+++ b/repos/base-hw/src/core/kernel/main.cc
@@ -36,6 +36,8 @@ class Kernel::Main
 
 		static Main *_instance;
 
+		Lock _data_lock { };
+
 		void _handle_kernel_entry();
 };
 
@@ -49,7 +51,7 @@ void Kernel::Main::_handle_kernel_entry()
 	Cpu_job * new_job;
 
 	{
-		Lock::Guard guard(data_lock());
+		Lock::Guard guard(_data_lock);
 
 		new_job = &cpu.schedule();
 	}
@@ -66,32 +68,34 @@ void Kernel::main_handle_kernel_entry()
 
 void Kernel::main_initialize_and_handle_kernel_entry()
 {
-	static volatile bool lock_ready   = false;
-	static volatile bool pool_ready   = false;
-	static volatile bool kernel_ready = false;
+	static volatile bool instance_initialized = false;
+	static volatile bool pool_ready           = false;
+	static volatile bool kernel_ready         = false;
 
-	/**
-	 * It is essential to guard the initialization of the data_lock object
-	 * in the SMP case, because otherwise the __cxa_guard_aquire of the cxx
-	 * library contention path might get called, which ends up in
-	 * calling a Semaphore, which will call Kernel::stop_thread() or
-	 * Kernel::yield() system-calls in this code
-	 */
-	while (Cpu::executing_id() != Cpu::primary_id() && !lock_ready) { }
+	bool const primary_cpu { Cpu::executing_id() == Cpu::primary_id() };
 
-	/**
-	 * Create a main object and initialize static reference to it
-	 */
-	if (Cpu::executing_id() == Cpu::primary_id()) {
+	if (primary_cpu) {
 
+		/**
+		 * Let the primary CPU create a Main object and initialize the static
+		 * reference to it.
+		 */
 		static Main instance { };
 		Main::_instance = &instance;
+
+	} else {
+
+		/**
+		 * Let secondary CPUs block until the primary CPU has managed to set
+		 * up the Main instance.
+		 */
+		while (!instance_initialized) { }
 	}
 
 	{
-		Lock::Guard guard(data_lock());
+		Lock::Guard guard(Main::_instance->_data_lock);
 
-		lock_ready = true;
+		instance_initialized = true;
 
 		/* initialize current cpu */
 		pool_ready = cpu_pool().initialize();
@@ -101,8 +105,8 @@ void Kernel::main_initialize_and_handle_kernel_entry()
 	while (!pool_ready) { ; }
 
 	/* the boot-cpu initializes the rest of the kernel */
-	if (Cpu::executing_id() == Cpu::primary_id()) {
-		Lock::Guard guard(data_lock());
+	if (primary_cpu) {
+		Lock::Guard guard(Main::_instance->_data_lock);
 
 		using Boot_info = Hw::Boot_info<Board::Boot_info>;
 		Boot_info &boot_info {
diff --git a/repos/base-hw/src/core/spec/arm/kernel/lock.cc b/repos/base-hw/src/core/spec/arm/kernel/lock.cc
index ae59d9ba36..f017b7e93d 100644
--- a/repos/base-hw/src/core/spec/arm/kernel/lock.cc
+++ b/repos/base-hw/src/core/spec/arm/kernel/lock.cc
@@ -11,20 +11,13 @@
  * under the terms of the GNU Affero General Public License version 3.
  */
 
-#include <base/lock_guard.h>
+/* Genode includes */
 #include <cpu/atomic.h>
 #include <cpu/memory_barrier.h>
 
+/* base-hw Core includes */
 #include <kernel/cpu.h>
 #include <kernel/lock.h>
-#include <kernel/kernel.h>
-
-
-Kernel::Lock & Kernel::data_lock()
-{
-	static Kernel::Lock lock;
-	return lock;
-}
 
 
 void Kernel::Lock::lock()