Initial source

1 files changed, 242 insertions, 0 deletions

diff --git a/kern/ast.c b/kern/ast.c
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+/*
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University.
+ * Copyright (c) 1993,1994 The University of Utah and
+ * the Computer Systems Laboratory (CSL).
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ *
+ * CARNEGIE MELLON, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
+ * THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM ANY LIABILITY
+ * OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF
+ * THIS SOFTWARE.
+ *
+ * Carnegie Mellon requests users of this software to return to
+ *
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ *
+ * any improvements or extensions that they make and grant Carnegie Mellon
+ * the rights to redistribute these changes.
+ */
+/*
+ *
+ *	This file contains routines to check whether an ast is needed.
+ *
+ *	ast_check() - check whether ast is needed for interrupt or context
+ *	switch.  Usually called by clock interrupt handler.
+ *
+ */
+
+#include <cpus.h>
+#include <mach_fixpri.h>
+#include <norma_ipc.h>
+
+#include <kern/ast.h>
+#include <kern/counters.h>
+#include "cpu_number.h"
+#include <kern/queue.h>
+#include <kern/sched.h>
+#include <kern/sched_prim.h>
+#include <kern/thread.h>
+#include <kern/processor.h>
+
+#include <machine/machspl.h>	/* for splsched */
+
+#if	MACH_FIXPRI
+#include <mach/policy.h>
+#endif	MACH_FIXPRI
+
+
+volatile ast_t need_ast[NCPUS];
+
+void
+ast_init()
+{
+#ifndef	MACHINE_AST
+	register int i;
+
+	for (i=0; i<NCPUS; i++)
+		need_ast[i] = 0;
+#endif	MACHINE_AST
+}
+
+void
+ast_taken()
+{
+	register thread_t self = current_thread();
+	register ast_t reasons;
+
+	/*
+	 *	Interrupts are still disabled.
+	 *	We must clear need_ast and then enable interrupts.
+	 */
+
+	reasons = need_ast[cpu_number()];
+	need_ast[cpu_number()] = AST_ZILCH;
+	(void) spl0();
+
+	/*
+	 *	These actions must not block.
+	 */
+
+	if (reasons & AST_NETWORK)
+		net_ast();
+
+#if	NORMA_IPC
+	if (reasons & AST_NETIPC)
+		netipc_ast();
+#endif	NORMA_IPC
+
+	/*
+	 *	Make darn sure that we don't call thread_halt_self
+	 *	or thread_block from the idle thread.
+	 */
+
+	if (self != current_processor()->idle_thread) {
+#ifndef MIGRATING_THREADS
+		while (thread_should_halt(self))
+			thread_halt_self();
+#endif
+
+		/*
+		 *	One of the previous actions might well have
+		 *	woken a high-priority thread, so we use
+		 *	csw_needed in addition to AST_BLOCK.
+		 */
+
+		if ((reasons & AST_BLOCK) ||
+		    csw_needed(self, current_processor())) {
+			counter(c_ast_taken_block++);
+			thread_block(thread_exception_return);
+		}
+	}
+}
+
+void
+ast_check()
+{
+	register int		mycpu = cpu_number();
+	register processor_t	myprocessor;
+	register thread_t	thread = current_thread();
+	register run_queue_t	rq;
+	spl_t			s = splsched();
+
+	/*
+	 *	Check processor state for ast conditions.
+	 */
+	myprocessor = cpu_to_processor(mycpu);
+	switch(myprocessor->state) {
+	    case PROCESSOR_OFF_LINE:
+	    case PROCESSOR_IDLE:
+	    case PROCESSOR_DISPATCHING:
+		/*
+		 *	No ast.
+		 */
+	    	break;
+
+#if	NCPUS > 1
+	    case PROCESSOR_ASSIGN:
+	    case PROCESSOR_SHUTDOWN:
+	        /*
+		 * 	Need ast to force action thread onto processor.
+		 *
+		 * XXX  Should check if action thread is already there.
+		 */
+		ast_on(mycpu, AST_BLOCK);
+		break;
+#endif	NCPUS > 1
+
+	    case PROCESSOR_RUNNING:
+
+		/*
+		 *	Propagate thread ast to processor.  If we already
+		 *	need an ast, don't look for more reasons.
+		 */
+		ast_propagate(thread, mycpu);
+		if (ast_needed(mycpu))
+			break;
+
+		/*
+		 *	Context switch check.  The csw_needed macro isn't
+		 *	used here because the rq->low hint may be wrong,
+		 *	and fixing it here avoids an extra ast.
+		 *	First check the easy cases.
+		 */
+		if (thread->state & TH_SUSP || myprocessor->runq.count > 0) {
+			ast_on(mycpu, AST_BLOCK);
+			break;
+		}
+
+		/*
+		 *	Update lazy evaluated runq->low if only timesharing.
+		 */
+#if	MACH_FIXPRI
+		if (myprocessor->processor_set->policies & POLICY_FIXEDPRI) {
+		    if (csw_needed(thread,myprocessor)) {
+			ast_on(mycpu, AST_BLOCK);
+			break;
+		    }
+		    else {
+			/*
+			 *	For fixed priority threads, set first_quantum
+			 *	so entire new quantum is used.
+			 */
+			if (thread->policy == POLICY_FIXEDPRI)
+			    myprocessor->first_quantum = TRUE;
+		    }
+		}
+		else {
+#endif	MACH_FIXPRI			
+		rq = &(myprocessor->processor_set->runq);
+		if (!(myprocessor->first_quantum) && (rq->count > 0)) {
+		    register queue_t 	q;
+		    /*
+		     *	This is not the first quantum, and there may
+		     *	be something in the processor_set runq.
+		     *	Check whether low hint is accurate.
+		     */
+		    q = rq->runq + *(volatile int *)&rq->low;
+		    if (queue_empty(q)) {
+			register int i;
+
+			/*
+			 *	Need to recheck and possibly update hint.
+			 */
+			simple_lock(&rq->lock);
+			q = rq->runq + rq->low;
+			if (rq->count > 0) {
+			    for (i = rq->low; i < NRQS; i++) {
+				if(!(queue_empty(q)))
+				    break;
+				q++;
+			    }
+			    rq->low = i;
+			}
+			simple_unlock(&rq->lock);
+		    }
+
+		    if (rq->low <= thread->sched_pri) {
+			ast_on(mycpu, AST_BLOCK);
+			break;
+		    }
+		}
+#if	MACH_FIXPRI
+		}
+#endif	MACH_FIXPRI
+		break;
+
+	    default:
+	        panic("ast_check: Bad processor state (cpu %d processor %08x) state: %d",
+			mycpu, myprocessor, myprocessor->state);
+	}
+
+	(void) splx(s);
+}