From 6503e5d9c6ab89ebb681b4819b07d3ff4890e5fb Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Sat, 11 Oct 2008 18:11:12 +0000
Subject: [PATCH] Added functions to pin a thread to the current CPU (i.e. it
 will only be scheduled on that CPU) and to avoid unscheduling it.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27974 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 headers/private/kernel/thread.h       | 28 +++++++++++++++++++++++++++
 headers/private/kernel/thread_types.h |  3 +++
 src/system/kernel/scheduler.cpp       | 17 +++++++++++++---
 src/system/kernel/thread.cpp          |  3 +++
 4 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/headers/private/kernel/thread.h b/headers/private/kernel/thread.h
index 9a3bdd83ef..864859b35b 100644
--- a/headers/private/kernel/thread.h
+++ b/headers/private/kernel/thread.h
@@ -205,4 +205,32 @@ thread_interrupt(struct thread* thread, bool kill)
 }
 
 
+static inline void
+thread_pin_to_current_cpu(struct thread* thread)
+{
+	thread->pinned_to_cpu++;
+}
+
+
+static inline void
+thread_unpin_from_current_cpu(struct thread* thread)
+{
+	thread->pinned_to_cpu--;
+}
+
+
+static inline void
+thread_disable_scheduling(struct thread* thread)
+{
+	thread->keep_scheduled++;
+}
+
+
+static inline void
+thread_enable_scheduling(struct thread* thread)
+{
+	thread->keep_scheduled--;
+}
+
+
 #endif /* _THREAD_H */
diff --git a/headers/private/kernel/thread_types.h b/headers/private/kernel/thread_types.h
index 9506c1ae31..0b4363073e 100644
--- a/headers/private/kernel/thread_types.h
+++ b/headers/private/kernel/thread_types.h
@@ -230,6 +230,9 @@ struct thread {
 	int32			state;
 	int32			next_state;
 	struct cpu_ent	*cpu;
+	struct cpu_ent	*previous_cpu;
+	int32			pinned_to_cpu;
+	int32			keep_scheduled;
 
 	sigset_t		sig_pending;
 	sigset_t		sig_block_mask;
diff --git a/src/system/kernel/scheduler.cpp b/src/system/kernel/scheduler.cpp
index 6f9fd85891..3a52c6e8d9 100644
--- a/src/system/kernel/scheduler.cpp
+++ b/src/system/kernel/scheduler.cpp
@@ -543,7 +543,7 @@ context_switch(struct thread *fromThread, struct thread *toThread)
 	if ((fromThread->flags & THREAD_FLAGS_DEBUGGER_INSTALLED) != 0)
 		user_debug_thread_unscheduled(fromThread);
 
-	toThread->cpu = fromThread->cpu;
+	toThread->previous_cpu = toThread->cpu = fromThread->cpu;
 	fromThread->cpu = NULL;
 
 	arch_thread_set_current_thread(toThread);
@@ -560,8 +560,11 @@ context_switch(struct thread *fromThread, struct thread *toThread)
 static int32
 reschedule_event(timer *unused)
 {
-	// this function is called as a result of the timer event set by the scheduler
-	// returning this causes a reschedule on the timer event
+	if (thread_get_current_thread()->keep_scheduled > 0)
+		return B_HANDLED_INTERRUPT;
+
+	// this function is called as a result of the timer event set by the
+	// scheduler returning this causes a reschedule on the timer event
 	thread_get_current_thread()->cpu->preempted = 1;
 	return B_INVOKE_SCHEDULER;
 }
@@ -617,6 +620,14 @@ scheduler_reschedule(void)
 				}
 #endif
 
+				// skip thread, if it doesn't want to run on this CPU
+				if (nextThread->pinned_to_cpu > 0
+					&& nextThread->previous_cpu != oldThread->cpu) {
+					prevThread = nextThread;
+					nextThread = nextThread->queue_next;
+					continue;
+				}
+
 				// always extract real time threads
 				if (nextThread->priority >= B_FIRST_REAL_TIME_PRIORITY)
 					break;
diff --git a/src/system/kernel/thread.cpp b/src/system/kernel/thread.cpp
index 46a251f74c..7e2706aa85 100644
--- a/src/system/kernel/thread.cpp
+++ b/src/system/kernel/thread.cpp
@@ -223,6 +223,9 @@ create_thread_struct(struct thread *inthread, const char *name,
 	thread->id = threadID >= 0 ? threadID : allocate_thread_id();
 	thread->team = NULL;
 	thread->cpu = cpu;
+	thread->previous_cpu = NULL;
+	thread->pinned_to_cpu = 0;
+	thread->keep_scheduled = 0;
 	thread->fault_handler = 0;
 	thread->page_faults_allowed = 1;
 	thread->kernel_stack_area = -1;