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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.
- */
- #include <mach/boolean.h>
- #include <mach/thread_switch.h>
- #include <ipc/ipc_port.h>
- #include <ipc/ipc_space.h>
- #include <kern/counters.h>
- #include <kern/ipc_kobject.h>
- #include <kern/mach_clock.h>
- #include <kern/printf.h>
- #include <kern/processor.h>
- #include <kern/sched.h>
- #include <kern/sched_prim.h>
- #include <kern/syscall_subr.h>
- #include <kern/ipc_sched.h>
- #include <kern/task.h>
- #include <kern/thread.h>
- #include <machine/machspl.h> /* for splsched */
- #if MACH_FIXPRI
- #include <mach/policy.h>
- #endif /* MACH_FIXPRI */
- /*
- * swtch and swtch_pri both attempt to context switch (logic in
- * thread_block no-ops the context switch if nothing would happen).
- * A boolean is returned that indicates whether there is anything
- * else runnable.
- *
- * This boolean can be used by a thread waiting on a
- * lock or condition: If FALSE is returned, the thread is justified
- * in becoming a resource hog by continuing to spin because there's
- * nothing else useful that the processor could do. If TRUE is
- * returned, the thread should make one more check on the
- * lock and then be a good citizen and really suspend.
- */
- void swtch_continue(void)
- {
- processor_t myprocessor;
- myprocessor = current_processor();
- thread_syscall_return(myprocessor->runq.count > 0 ||
- myprocessor->processor_set->runq.count > 0);
- /*NOTREACHED*/
- }
- boolean_t swtch(void)
- {
- processor_t myprocessor;
- #if NCPUS > 1
- myprocessor = current_processor();
- if (myprocessor->runq.count == 0 &&
- myprocessor->processor_set->runq.count == 0)
- return(FALSE);
- #endif /* NCPUS > 1 */
- counter(c_swtch_block++);
- thread_block(swtch_continue);
- myprocessor = current_processor();
- return(myprocessor->runq.count > 0 ||
- myprocessor->processor_set->runq.count > 0);
- }
- void swtch_pri_continue(void)
- {
- thread_t thread = current_thread();
- processor_t myprocessor;
- if (thread->depress_priority >= 0)
- (void) thread_depress_abort(thread);
- myprocessor = current_processor();
- thread_syscall_return(myprocessor->runq.count > 0 ||
- myprocessor->processor_set->runq.count > 0);
- /*NOTREACHED*/
- }
- boolean_t swtch_pri(int pri)
- {
- thread_t thread = current_thread();
- processor_t myprocessor;
- #if NCPUS > 1
- myprocessor = current_processor();
- if (myprocessor->runq.count == 0 &&
- myprocessor->processor_set->runq.count == 0)
- return(FALSE);
- #endif /* NCPUS > 1 */
- /*
- * XXX need to think about depression duration.
- * XXX currently using min quantum.
- */
- thread_depress_priority(thread, min_quantum);
- counter(c_swtch_pri_block++);
- thread_block(swtch_pri_continue);
- if (thread->depress_priority >= 0)
- (void) thread_depress_abort(thread);
- myprocessor = current_processor();
- return(myprocessor->runq.count > 0 ||
- myprocessor->processor_set->runq.count > 0);
- }
- void thread_switch_continue(void)
- {
- thread_t cur_thread = current_thread();
- /*
- * Restore depressed priority
- */
- if (cur_thread->depress_priority >= 0)
- (void) thread_depress_abort(cur_thread);
- thread_syscall_return(KERN_SUCCESS);
- /*NOTREACHED*/
- }
- /*
- * thread_switch:
- *
- * Context switch. User may supply thread hint.
- *
- * Fixed priority threads that call this get what they asked for
- * even if that violates priority order.
- */
- kern_return_t thread_switch(
- mach_port_t thread_name,
- int option,
- mach_msg_timeout_t option_time)
- {
- thread_t cur_thread = current_thread();
- processor_t myprocessor;
- ipc_port_t port;
- /*
- * Process option.
- */
- switch (option) {
- case SWITCH_OPTION_NONE:
- /*
- * Nothing to do.
- */
- break;
- case SWITCH_OPTION_DEPRESS:
- /*
- * Depress priority for given time.
- */
- thread_depress_priority(cur_thread, option_time);
- break;
- case SWITCH_OPTION_WAIT:
- thread_will_wait_with_timeout(cur_thread, option_time);
- break;
- default:
- return(KERN_INVALID_ARGUMENT);
- }
- #ifndef MIGRATING_THREADS /* XXX thread_run defunct */
- /*
- * Check and act on thread hint if appropriate.
- */
- if ((thread_name != 0) &&
- (ipc_port_translate_send(cur_thread->task->itk_space,
- thread_name, &port) == KERN_SUCCESS)) {
- /* port is locked, but it might not be active */
- /*
- * Get corresponding thread.
- */
- if (ip_active(port) && (ip_kotype(port) == IKOT_THREAD)) {
- thread_t thread;
- spl_t s;
- thread = (thread_t) port->ip_kobject;
- /*
- * Check if the thread is in the right pset. Then
- * pull it off its run queue. If it
- * doesn't come, then it's not eligible.
- */
- s = splsched();
- thread_lock(thread);
- if ((thread->processor_set == cur_thread->processor_set)
- && (rem_runq(thread) != RUN_QUEUE_NULL)) {
- /*
- * Hah, got it!!
- */
- thread_unlock(thread);
- (void) splx(s);
- ip_unlock(port);
- /* XXX thread might disappear on us now? */
- #if MACH_FIXPRI
- if (thread->policy == POLICY_FIXEDPRI) {
- myprocessor = current_processor();
- myprocessor->quantum = thread->sched_data;
- myprocessor->first_quantum = TRUE;
- }
- #endif /* MACH_FIXPRI */
- counter(c_thread_switch_handoff++);
- thread_run(thread_switch_continue, thread);
- /*
- * Restore depressed priority
- */
- if (cur_thread->depress_priority >= 0)
- (void) thread_depress_abort(cur_thread);
- return(KERN_SUCCESS);
- }
- thread_unlock(thread);
- (void) splx(s);
- }
- ip_unlock(port);
- }
- #endif /* not MIGRATING_THREADS */
- /*
- * No handoff hint supplied, or hint was wrong. Call thread_block() in
- * hopes of running something else. If nothing else is runnable,
- * thread_block will detect this. WARNING: thread_switch with no
- * option will not do anything useful if the thread calling it is the
- * highest priority thread (can easily happen with a collection
- * of timesharing threads).
- */
- #if NCPUS > 1
- myprocessor = current_processor();
- if (myprocessor->processor_set->runq.count > 0 ||
- myprocessor->runq.count > 0)
- #endif /* NCPUS > 1 */
- {
- counter(c_thread_switch_block++);
- thread_block(thread_switch_continue);
- }
- /*
- * Restore depressed priority
- */
- if (cur_thread->depress_priority >= 0)
- (void) thread_depress_abort(cur_thread);
- return(KERN_SUCCESS);
- }
- /*
- * thread_depress_priority
- *
- * Depress thread's priority to lowest possible for specified period.
- * Intended for use when thread wants a lock but doesn't know which
- * other thread is holding it. As with thread_switch, fixed
- * priority threads get exactly what they asked for. Users access
- * this by the SWITCH_OPTION_DEPRESS option to thread_switch. A Time
- * of zero will result in no timeout being scheduled.
- */
- void
- thread_depress_priority(
- thread_t thread,
- mach_msg_timeout_t depress_time)
- {
- unsigned int ticks;
- spl_t s;
- /* convert from milliseconds to ticks */
- ticks = convert_ipc_timeout_to_ticks(depress_time);
- s = splsched();
- thread_lock(thread);
- /*
- * If thread is already depressed, override previous depression.
- */
- reset_timeout_check(&thread->depress_timer);
- /*
- * Save current priority, then set priority and
- * sched_pri to their lowest possible values.
- */
- thread->depress_priority = thread->priority;
- thread->priority = NRQS-1;
- thread->sched_pri = NRQS-1;
- if (ticks != 0)
- set_timeout(&thread->depress_timer, ticks);
- thread_unlock(thread);
- (void) splx(s);
- }
- /*
- * thread_depress_timeout:
- *
- * Timeout routine for priority depression.
- */
- void
- thread_depress_timeout(thread_t thread)
- {
- spl_t s;
- s = splsched();
- thread_lock(thread);
- /*
- * If we lose a race with thread_depress_abort,
- * then depress_priority might be -1.
- */
- if (thread->depress_priority >= 0) {
- thread->priority = thread->depress_priority;
- thread->depress_priority = -1;
- compute_priority(thread, FALSE);
- }
- thread_unlock(thread);
- (void) splx(s);
- }
- /*
- * thread_depress_abort:
- *
- * Prematurely abort priority depression if there is one.
- */
- kern_return_t
- thread_depress_abort(thread_t thread)
- {
- spl_t s;
- if (thread == THREAD_NULL)
- return(KERN_INVALID_ARGUMENT);
- s = splsched();
- thread_lock(thread);
- /*
- * Only restore priority if thread is depressed.
- */
- if (thread->depress_priority >= 0) {
- reset_timeout_check(&thread->depress_timer);
- thread->priority = thread->depress_priority;
- thread->depress_priority = -1;
- compute_priority(thread, FALSE);
- }
- thread_unlock(thread);
- (void) splx(s);
- return(KERN_SUCCESS);
- }
- /*
- * mach_print
- *
- * Display a null-terminated character string on the Mach console.
- * This system call is meant as a debugging tool useful to circumvent
- * messaging altogether.
- */
- #ifdef MACH_KDB
- void
- mach_print(const char *s)
- {
- printf("%s", s);
- }
- #endif /* MACH_KDB */
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