From 8cc24e048e95c56007e8aa5cd2f5a15b9b43a6db Mon Sep 17 00:00:00 2001
From: Stefan Kalkowski <stefan.kalkowski@genode-labs.com>
Date: Fri, 11 Apr 2025 14:56:14 +0200
Subject: [PATCH] fixup "hw: sanitize scheduler, cpu, and timer interplay"
 (timer)

---
 repos/base-hw/src/core/kernel/scheduler.cc |  4 +--
 repos/base-hw/src/core/kernel/thread.cc    |  2 +-
 repos/base-hw/src/core/kernel/timer.cc     | 31 ++++++++++++----------
 repos/base-hw/src/core/kernel/timer.h      |  9 +++----
 4 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/repos/base-hw/src/core/kernel/scheduler.cc b/repos/base-hw/src/core/kernel/scheduler.cc
index e9fd8d1d2a..ce80b20c83 100644
--- a/repos/base-hw/src/core/kernel/scheduler.cc
+++ b/repos/base-hw/src/core/kernel/scheduler.cc
@@ -186,10 +186,8 @@ void Scheduler::update()
 		if (!_schedule_slack())
 			_set_current(_idle, _slack_quota);
 
-	_timer.set_timeout(&_timeout,
+	_timer.set_timeout(_timeout,
 	                   Genode::min(_current_quantum, _super_period_left));
-	_timer.schedule_timeout();
-
 }
 
 
diff --git a/repos/base-hw/src/core/kernel/thread.cc b/repos/base-hw/src/core/kernel/thread.cc
index fafe75e07f..e7f80f9b8f 100644
--- a/repos/base-hw/src/core/kernel/thread.cc
+++ b/repos/base-hw/src/core/kernel/thread.cc
@@ -507,7 +507,7 @@ void Thread::_call_timeout()
 {
 	Timer & t = _cpu().timer();
 	_timeout_sigid = (Kernel::capid_t)user_arg_2();
-	t.set_timeout(this, t.us_to_ticks(user_arg_1()));
+	t.set_timeout(*this, t.us_to_ticks(user_arg_1()));
 }
 
 
diff --git a/repos/base-hw/src/core/kernel/timer.cc b/repos/base-hw/src/core/kernel/timer.cc
index 39ecf8df70..f6255db6e4 100644
--- a/repos/base-hw/src/core/kernel/timer.cc
+++ b/repos/base-hw/src/core/kernel/timer.cc
@@ -36,19 +36,19 @@ time_t Timer::timeout_max_us() const
 }
 
 
-void Timer::set_timeout(Timeout * const timeout, time_t const duration)
+void Timer::set_timeout(Timeout &timeout, time_t const duration)
 {
 	/*
 	 * Remove timeout if it is already in use. Timeouts may get overridden as
 	 * result of an update.
 	 */
-	if (timeout->_listed)
-		_timeout_list.remove(timeout);
+	if (timeout._listed)
+		_timeout_list.remove(&timeout);
 	else
-		timeout->_listed = true;
+		timeout._listed = true;
 
 	/* set timeout parameters */
-	timeout->_end = time() + duration;
+	timeout._end = time() + duration;
 
 	/*
 	 * Insert timeout. Timeouts are ordered ascending according to their end
@@ -56,26 +56,26 @@ void Timer::set_timeout(Timeout * const timeout, time_t const duration)
 	 */
 	Timeout * t1 = 0;
 	for (Timeout * t2 = _timeout_list.first();
-	     t2 && t2->_end < timeout->_end;
+	     t2 && t2->_end < timeout._end;
 	     t1 = t2, t2 = t2->next()) { }
 
-	_timeout_list.insert(timeout, t1);
+	_timeout_list.insert(&timeout, t1);
+
+	if (_timeout_list.first() == &timeout)
+		_schedule_timeout();
 }
 
 
-time_t Timer::schedule_timeout()
+void Timer::_schedule_timeout()
 {
 	/* get the timeout with the nearest end time */
 	Timeout * timeout = _timeout_list.first();
-	assert(timeout);
+	time_t end = timeout ? timeout->_end : _time + _max_value();
 
 	/* install timeout at timer hardware */
-	time_t duration = _duration();
-	_time          += duration;
-	_last_timeout_duration = (timeout->_end > _time) ? timeout->_end - _time : 1;
+	_time += _duration();
+	_last_timeout_duration = (end > _time) ? end - _time : 1;
 	_start_one_shot(_last_timeout_duration);
-
-	return duration;
 }
 
 
@@ -97,6 +97,9 @@ void Timer::_process_timeouts()
 		timeout->_listed = false;
 		timeout->timeout_triggered();
 	}
+
+	if (_timeout_list.first())
+		_schedule_timeout();
 }
 
 
diff --git a/repos/base-hw/src/core/kernel/timer.h b/repos/base-hw/src/core/kernel/timer.h
index ac92d2bfca..09c2dc6508 100644
--- a/repos/base-hw/src/core/kernel/timer.h
+++ b/repos/base-hw/src/core/kernel/timer.h
@@ -90,16 +90,13 @@ class Kernel::Timer
 
 		void _process_timeouts();
 
+		void _schedule_timeout();
+
 	public:
 
 		Timer(Cpu & cpu);
 
-		/**
-		 * Return duration from last call of this function
-		 */
-		time_t schedule_timeout();
-
-		void set_timeout(Timeout * const timeout, time_t const duration);
+		void set_timeout(Timeout &timeout, time_t const duration);
 
 		time_t us_to_ticks(time_t const us) const;