[PATCH gnumach v1 1/4] initialise max_priority to BASEPRI_SYSTEM

From: Diego Nieto Cid <[email protected]>

Set the default thread and processor set max priority to
that of system threads to allow privileged task to raise
its own priority.

  * kern/processor.c: modify pset_init to set the initial
                      max_priority to BASEPRI_SYSTE.
  * kern/thread.c: set the thread template max_priority to
                   BASEPRI_SYSTEM.
---
 kern/processor.c |  6 +++---
 kern/thread.c    | 12 +++++++++++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/kern/processor.c b/kern/processor.c
index ee1f7694..485eb51b 100644
--- a/kern/processor.c
+++ b/kern/processor.c
@@ -91,8 +91,8 @@ void pset_sys_bootstrap(void)
 	default_pset.active = TRUE;
 
 	/*
-	 *	Note: the default_pset has a max_priority of BASEPRI_USER.
-	 *	Internal kernel threads override this in kernel_thread.
+	 *	Note: the default_pset has a max_priority of BASEPRI_SYSTEM
+	 *	so that privileged tasks can raise its priority later on.
 	 */
 }
 
@@ -160,7 +160,7 @@ void pset_init(
 	simple_lock_init(&pset->lock);
 	pset->pset_self = IP_NULL;
 	pset->pset_name_self = IP_NULL;
-	pset->max_priority = BASEPRI_USER;
+	pset->max_priority = BASEPRI_SYSTEM;
 #if	MACH_FIXPRI
 	pset->policies = POLICY_TIMESHARE;
 #endif	/* MACH_FIXPRI */
diff --git a/kern/thread.c b/kern/thread.c
index deb9688d..5a0989ae 100644
--- a/kern/thread.c
+++ b/kern/thread.c
@@ -335,7 +335,11 @@ void thread_init(void)
 	thread_template.swap_func = thread_bootstrap_return;
 
 /*	thread_template.priority (later) */
-	thread_template.max_priority = BASEPRI_USER;
+	/*
+	 *	Set an a priori max priority, but avoid going
+	 *	higher than SYSTEM threads.
+	 */
+	thread_template.max_priority = BASEPRI_SYSTEM;
 /*	thread_template.sched_pri (later - compute_priority) */
 #if	MACH_FIXPRI
 	thread_template.sched_data = 0;
@@ -1736,6 +1740,12 @@ thread_t kernel_thread(
 	 *	The swapin mechanism might not be operational yet.
 	 */
 	thread_doswapin(thread);
+	/*
+	 *	task_create above, computed the max_priority from
+	 *	the task and processor set's max_priority.
+	 *	Since this is a kernel thread, set its max_priority
+	 *	to BASEPRI_SYSTEM.
+	 */
 	thread->max_priority = BASEPRI_SYSTEM;
 	thread->priority = BASEPRI_SYSTEM;
 	thread->sched_pri = BASEPRI_SYSTEM;
-- 
2.53.0