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Diffstat (limited to 'kern/ast.c')
| -rw-r--r-- | kern/ast.c | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/kern/ast.c b/kern/ast.c new file mode 100644 index 0000000..fc26f94 --- /dev/null +++ b/kern/ast.c @@ -0,0 +1,242 @@ +/* + * 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); +} |