From 8e252f79f82d50cd9566548d95f6ca8a7ff12be1 Mon Sep 17 00:00:00 2001
From: Christian Prochaska <christian.prochaska@genode-labs.com>
Date: Mon, 20 Dec 2021 13:52:27 +0100
Subject: [PATCH] Remove mutex from 'Genode::Trace_output'

Fixes #4356
---
 repos/base/include/base/log.h            | 25 +++++++++++++++---------
 repos/base/lib/symbols/ld                |  3 +--
 repos/base/src/lib/base/default_log.cc   | 10 +---------
 repos/base/src/lib/base/log.cc           | 16 +++------------
 repos/os/src/server/log_terminal/main.cc |  3 ++-
 5 files changed, 23 insertions(+), 34 deletions(-)

diff --git a/repos/base/include/base/log.h b/repos/base/include/base/log.h
index 1e4d9e4bf3..89d00d32b6 100644
--- a/repos/base/include/base/log.h
+++ b/repos/base/include/base/log.h
@@ -15,6 +15,7 @@
 #define _INCLUDE__BASE__LOG_H_
 
 #include <base/output.h>
+#include <base/buffered_output.h>
 #include <base/mutex.h>
 #include <trace/timestamp.h>
 
@@ -107,23 +108,29 @@ class Genode::Trace_output
 {
 	private:
 
-		Mutex _mutex { };
+		struct Write_trace_fn
+		{
+			void operator () (char const *);
+		};
 
-		Output &_output;
-
-		void _acquire();
-		void _release();
+		/* cannot include log_session.h here because of recursion */
+		enum { LOG_SESSION_MAX_STRING_LEN = 232 };
+		typedef Buffered_output<LOG_SESSION_MAX_STRING_LEN,
+		                        Write_trace_fn>
+		        Buffered_trace_output;
 
 	public:
 
-		Trace_output(Output &output) : _output(output) { }
+		Trace_output() { }
 
 		template <typename... ARGS>
 		void output(ARGS &&... args)
 		{
-			_acquire();
-			Output::out_args(_output, args...);
-			_release();
+			Buffered_trace_output buffered_trace_output
+			{ Write_trace_fn() };
+
+			Output::out_args(buffered_trace_output, args...);
+			buffered_trace_output.out_string("\n");
 		}
 
 		/**
diff --git a/repos/base/lib/symbols/ld b/repos/base/lib/symbols/ld
index 7c50906994..4d47f01de2 100644
--- a/repos/base/lib/symbols/ld
+++ b/repos/base/lib/symbols/ld
@@ -73,8 +73,7 @@ _ZN6Genode11Sliced_heapD2Ev T
 _ZN6Genode12Address_infoC1Em T
 _ZN6Genode12Address_infoC2Em T
 _ZN6Genode12Trace_output12trace_outputEv T
-_ZN6Genode12Trace_output8_acquireEv T
-_ZN6Genode12Trace_output8_releaseEv T
+_ZN6Genode12Trace_output14Write_trace_fnclEPKc T
 _ZN6Genode13Avl_node_base15_rotate_subtreeEPS0_bRNS0_6PolicyE T
 _ZN6Genode13Avl_node_base18_rebalance_subtreeEPS0_RNS0_6PolicyE T
 _ZN6Genode13Avl_node_base6_adoptEPS0_bRNS0_6PolicyE T
diff --git a/repos/base/src/lib/base/default_log.cc b/repos/base/src/lib/base/default_log.cc
index 598dd457b5..161b9144cd 100644
--- a/repos/base/src/lib/base/default_log.cc
+++ b/repos/base/src/lib/base/default_log.cc
@@ -114,14 +114,6 @@ void Genode::init_log(Parent &parent)
 	log_ptr = unmanaged_singleton<Log>(*buffered_log_output);
 
 	/* enable trace back end */
-	struct Write_trace_fn { void operator () (char const *s) { Thread::trace(s); } };
-
-	typedef Buffered_output<Log_session::MAX_STRING_LEN, Write_trace_fn>
-	        Buffered_trace_output;
-
-	static Buffered_trace_output *buffered_trace_output =
-		unmanaged_singleton<Buffered_trace_output>(Write_trace_fn());
-
-	trace_ptr = unmanaged_singleton<Trace_output>(*buffered_trace_output);
+	trace_ptr = unmanaged_singleton<Trace_output>();
 }
 
diff --git a/repos/base/src/lib/base/log.cc b/repos/base/src/lib/base/log.cc
index 978414ddce..ef0bffac5f 100644
--- a/repos/base/src/lib/base/log.cc
+++ b/repos/base/src/lib/base/log.cc
@@ -13,6 +13,7 @@
 
 /* Genode includes */
 #include <base/log.h>
+#include <base/thread.h>
 
 using namespace Genode;
 
@@ -61,18 +62,7 @@ void Raw::_release()
 }
 
 
-void Trace_output::_acquire()
+void Trace_output::Write_trace_fn::operator () (char const *s)
 {
-	_mutex.acquire();
-}
-
-
-void Trace_output::_release()
-{
-	/*
-	 * Add newline
-	 */
-	_output.out_string("\n");
-
-	_mutex.release();
+	Thread::trace(s);
 }
diff --git a/repos/os/src/server/log_terminal/main.cc b/repos/os/src/server/log_terminal/main.cc
index 4ce160a66b..36e431aba3 100644
--- a/repos/os/src/server/log_terminal/main.cc
+++ b/repos/os/src/server/log_terminal/main.cc
@@ -24,6 +24,7 @@ namespace Terminal {
 	class Session_component;
 	class Root_component;
 	class Main;
+	class Buffered_output;
 
 	using namespace Genode;
 };
@@ -32,7 +33,7 @@ namespace Terminal {
 /**
  * Utility for the buffered output of small successive write operations
  */
-class Buffered_output
+class Terminal::Buffered_output
 {
 	private: