From 45cab8fed6fbad931c2affa81c94c98b6631bf7e Mon Sep 17 00:00:00 2001
From: Stefan Kalkowski <stefan.kalkowski@genode-labs.com>
Date: Wed, 8 Mar 2017 10:26:39 +0100
Subject: [PATCH] hw: destroy active scheduling context (fix #1537)

* In addition fixes routes of the cpu_scheduler.run test
---
 repos/base-hw/run/cpu_scheduler.run           |  4 +++
 .../base-hw/src/core/kernel/cpu_scheduler.cc  | 25 ++++++++-----------
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/repos/base-hw/run/cpu_scheduler.run b/repos/base-hw/run/cpu_scheduler.run
index 05e4c57e7..75e458b15 100644
--- a/repos/base-hw/run/cpu_scheduler.run
+++ b/repos/base-hw/run/cpu_scheduler.run
@@ -16,6 +16,10 @@ install_config {
 		<parent-provides>
 			<service name="LOG"/>
 			<service name="RM"/>
+			<service name="RAM"/>
+			<service name="PD"/>
+			<service name="CPU"/>
+			<service name="ROM"/>
 		</parent-provides>
 		<default-route>
 			<any-service> <parent/> </any-service>
diff --git a/repos/base-hw/src/core/kernel/cpu_scheduler.cc b/repos/base-hw/src/core/kernel/cpu_scheduler.cc
index ad34fdbd9..33b2c5492 100644
--- a/repos/base-hw/src/core/kernel/cpu_scheduler.cc
+++ b/repos/base-hw/src/core/kernel/cpu_scheduler.cc
@@ -132,10 +132,14 @@ void Cpu_scheduler::_quota_adaption(Share * const s, unsigned const q)
 
 void Cpu_scheduler::update(unsigned q)
 {
-	unsigned const r = _trim_consumption(q);
-	if (_head_claims) { _head_claimed(r); }
-	else { _head_filled(r); }
-	_consumed(q);
+	/* do not detract the quota if the head context was removed even now */
+	if (_head) {
+		unsigned const r = _trim_consumption(q);
+		if (_head_claims) { _head_claimed(r); }
+		else              { _head_filled(r);  }
+		_consumed(q);
+	}
+
 	if (_claim_for_head()) { return; }
 	if (_fill_for_head()) { return; }
 	_set_head(_idle, _fill, 0);
@@ -144,6 +148,8 @@ void Cpu_scheduler::update(unsigned q)
 
 bool Cpu_scheduler::ready_check(Share * const s1)
 {
+	assert(_head);
+
 	ready(s1);
 	Share * s2 = _head;
 	if (!s1->_claim) { return s2 == _idle; }
@@ -185,16 +191,7 @@ void Cpu_scheduler::remove(Share * const s)
 {
 	assert(s != _idle);
 
-	/*
-	 * FIXME
-	 * Thanks to helping, this can happen and shall not be treated as bad
-	 * behavior. But by now, we have no stable solution for it.
-	 *
-	 */
-	if (s == _head) {
-		Genode::error("Removing the head of the CPU scheduler isn't supported by now.");
-		while (1) ;
-	}
+	if (s == _head) _head = nullptr;
 	if (s->_ready) { _fills.remove(s); }
 	if (!s->_quota) { return; }
 	if (s->_ready) { _rcl[s->_prio].remove(s); }