/* $OpenBSD: kern_synch.c,v 1.190 2022/08/14 01:58:27 jsg Exp $ */ /* $NetBSD: kern_synch.c,v 1.37 1996/04/22 01:38:37 christos Exp $ */ /* * Copyright (c) 1982, 1986, 1990, 1991, 1993 * The Regents of the University of California. All rights reserved. * (c) UNIX System Laboratories, Inc. * All or some portions of this file are derived from material licensed * to the University of California by American Telephone and Telegraph * Co. or Unix System Laboratories, Inc. and are reproduced herein with * the permission of UNIX System Laboratories, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)kern_synch.c 8.6 (Berkeley) 1/21/94 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef DIAGNOSTIC #include #endif #ifdef KTRACE #include #endif int sleep_signal_check(void); int thrsleep(struct proc *, struct sys___thrsleep_args *); int thrsleep_unlock(void *); /* * We're only looking at 7 bits of the address; everything is * aligned to 4, lots of things are aligned to greater powers * of 2. Shift right by 8, i.e. drop the bottom 256 worth. */ #define TABLESIZE 128 #define LOOKUP(x) (((long)(x) >> 8) & (TABLESIZE - 1)) TAILQ_HEAD(slpque,proc) slpque[TABLESIZE]; void sleep_queue_init(void) { int i; for (i = 0; i < TABLESIZE; i++) TAILQ_INIT(&slpque[i]); } /* * Global sleep channel for threads that do not want to * receive wakeup(9) broadcasts. */ int nowake; /* * During autoconfiguration or after a panic, a sleep will simply * lower the priority briefly to allow interrupts, then return. * The priority to be used (safepri) is machine-dependent, thus this * value is initialized and maintained in the machine-dependent layers. * This priority will typically be 0, or the lowest priority * that is safe for use on the interrupt stack; it can be made * higher to block network software interrupts after panics. */ extern int safepri; /* * General sleep call. Suspends the current process until a wakeup is * performed on the specified identifier. The process will then be made * runnable with the specified priority. Sleeps at most timo/hz seconds * (0 means no timeout). If pri includes PCATCH flag, signals are checked * before and after sleeping, else signals are not checked. Returns 0 if * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a * signal needs to be delivered, ERESTART is returned if the current system * call should be restarted if possible, and EINTR is returned if the system * call should be interrupted by the signal (return EINTR). */ int tsleep(const volatile void *ident, int priority, const char *wmesg, int timo) { struct sleep_state sls; #ifdef MULTIPROCESSOR int hold_count; #endif KASSERT((priority & ~(PRIMASK | PCATCH)) == 0); KASSERT(ident != &nowake || ISSET(priority, PCATCH) || timo != 0); #ifdef MULTIPROCESSOR KASSERT(timo || _kernel_lock_held()); #endif #ifdef DDB if (cold == 2) db_stack_dump(); #endif if (cold || panicstr) { int s; /* * After a panic, or during autoconfiguration, * just give interrupts a chance, then just return; * don't run any other procs or panic below, * in case this is the idle process and already asleep. */ s = splhigh(); splx(safepri); #ifdef MULTIPROCESSOR if (_kernel_lock_held()) { hold_count = __mp_release_all(&kernel_lock); __mp_acquire_count(&kernel_lock, hold_count); } #endif splx(s); return (0); } sleep_setup(&sls, ident, priority, wmesg, timo); return sleep_finish(&sls, 1); } int tsleep_nsec(const volatile void *ident, int priority, const char *wmesg, uint64_t nsecs) { uint64_t to_ticks; if (nsecs == INFSLP) return tsleep(ident, priority, wmesg, 0); #ifdef DIAGNOSTIC if (nsecs == 0) { log(LOG_WARNING, "%s: %s[%d]: %s: trying to sleep zero nanoseconds\n", __func__, curproc->p_p->ps_comm, curproc->p_p->ps_pid, wmesg); } #endif /* * We want to sleep at least nsecs nanoseconds worth of ticks. * * - Clamp nsecs to prevent arithmetic overflow. * * - Round nsecs up to account for any nanoseconds that do not * divide evenly into tick_nsec, otherwise we'll lose them to * integer division in the next step. We add (tick_nsec - 1) * to keep from introducing a spurious tick if there are no * such nanoseconds, i.e. nsecs % tick_nsec == 0. * * - Divide the rounded value to a count of ticks. We divide * by (tick_nsec + 1) to discard the extra tick introduced if, * before rounding, nsecs % tick_nsec == 1. * * - Finally, add a tick to the result. We need to wait out * the current tick before we can begin counting our interval, * as we do not know how much time has elapsed since the * current tick began. */ nsecs = MIN(nsecs, UINT64_MAX - tick_nsec); to_ticks = (nsecs + tick_nsec - 1) / (tick_nsec + 1) + 1; if (to_ticks > INT_MAX) to_ticks = INT_MAX; return tsleep(ident, priority, wmesg, (int)to_ticks); } /* * Same as tsleep, but if we have a mutex provided, then once we've * entered the sleep queue we drop the mutex. After sleeping we re-lock. */ int msleep(const volatile void *ident, struct mutex *mtx, int priority, const char *wmesg, int timo) { struct sleep_state sls; int error, spl; #ifdef MULTIPROCESSOR int hold_count; #endif KASSERT((priority & ~(PRIMASK | PCATCH | PNORELOCK)) == 0); KASSERT(ident != &nowake || ISSET(priority, PCATCH) || timo != 0); KASSERT(mtx != NULL); #ifdef DDB if (cold == 2) db_stack_dump(); #endif if (cold || panicstr) { /* * After a panic, or during autoconfiguration, * just give interrupts a chance, then just return; * don't run any other procs or panic below, * in case this is the idle process and already asleep. */ spl = MUTEX_OLDIPL(mtx); MUTEX_OLDIPL(mtx) = safepri; mtx_leave(mtx); #ifdef MULTIPROCESSOR if (_kernel_lock_held()) { hold_count = __mp_release_all(&kernel_lock); __mp_acquire_count(&kernel_lock, hold_count); } #endif if ((priority & PNORELOCK) == 0) { mtx_enter(mtx); MUTEX_OLDIPL(mtx) = spl; } else splx(spl); return (0); } sleep_setup(&sls, ident, priority, wmesg, timo); /* XXX - We need to make sure that the mutex doesn't * unblock splsched. This can be made a bit more * correct when the sched_lock is a mutex. */ spl = MUTEX_OLDIPL(mtx); MUTEX_OLDIPL(mtx) = splsched(); mtx_leave(mtx); /* signal may stop the process, release mutex before that */ error = sleep_finish(&sls, 1); if ((priority & PNORELOCK) == 0) { mtx_enter(mtx); MUTEX_OLDIPL(mtx) = spl; /* put the ipl back */ } else splx(spl); return error; } int msleep_nsec(const volatile void *ident, struct mutex *mtx, int priority, const char *wmesg, uint64_t nsecs) { uint64_t to_ticks; if (nsecs == INFSLP) return msleep(ident, mtx, priority, wmesg, 0); #ifdef DIAGNOSTIC if (nsecs == 0) { log(LOG_WARNING, "%s: %s[%d]: %s: trying to sleep zero nanoseconds\n", __func__, curproc->p_p->ps_comm, curproc->p_p->ps_pid, wmesg); } #endif nsecs = MIN(nsecs, UINT64_MAX - tick_nsec); to_ticks = (nsecs + tick_nsec - 1) / (tick_nsec + 1) + 1; if (to_ticks > INT_MAX) to_ticks = INT_MAX; return msleep(ident, mtx, priority, wmesg, (int)to_ticks); } /* * Same as tsleep, but if we have a rwlock provided, then once we've * entered the sleep queue we drop the it. After sleeping we re-lock. */ int rwsleep(const volatile void *ident, struct rwlock *rwl, int priority, const char *wmesg, int timo) { struct sleep_state sls; int error, status; KASSERT((priority & ~(PRIMASK | PCATCH | PNORELOCK)) == 0); KASSERT(ident != &nowake || ISSET(priority, PCATCH) || timo != 0); rw_assert_anylock(rwl); status = rw_status(rwl); sleep_setup(&sls, ident, priority, wmesg, timo); rw_exit(rwl); /* signal may stop the process, release rwlock before that */ error = sleep_finish(&sls, 1); if ((priority & PNORELOCK) == 0) rw_enter(rwl, status); return error; } int rwsleep_nsec(const volatile void *ident, struct rwlock *rwl, int priority, const char *wmesg, uint64_t nsecs) { uint64_t to_ticks; if (nsecs == INFSLP) return rwsleep(ident, rwl, priority, wmesg, 0); #ifdef DIAGNOSTIC if (nsecs == 0) { log(LOG_WARNING, "%s: %s[%d]: %s: trying to sleep zero nanoseconds\n", __func__, curproc->p_p->ps_comm, curproc->p_p->ps_pid, wmesg); } #endif nsecs = MIN(nsecs, UINT64_MAX - tick_nsec); to_ticks = (nsecs + tick_nsec - 1) / (tick_nsec + 1) + 1; if (to_ticks > INT_MAX) to_ticks = INT_MAX; return rwsleep(ident, rwl, priority, wmesg, (int)to_ticks); } void sleep_setup(struct sleep_state *sls, const volatile void *ident, int prio, const char *wmesg, int timo) { struct proc *p = curproc; #ifdef DIAGNOSTIC if (p->p_flag & P_CANTSLEEP) panic("sleep: %s failed insomnia", p->p_p->ps_comm); if (ident == NULL) panic("tsleep: no ident"); if (p->p_stat != SONPROC) panic("tsleep: not SONPROC"); #endif sls->sls_catch = prio & PCATCH; sls->sls_timeout = 0; SCHED_LOCK(sls->sls_s); TRACEPOINT(sched, sleep, NULL); p->p_wchan = ident; p->p_wmesg = wmesg; p->p_slptime = 0; p->p_slppri = prio & PRIMASK; TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_runq); if (timo) { KASSERT((p->p_flag & P_TIMEOUT) == 0); sls->sls_timeout = 1; timeout_add(&p->p_sleep_to, timo); } } int sleep_finish(struct sleep_state *sls, int do_sleep) { struct proc *p = curproc; int error = 0, error1 = 0; if (sls->sls_catch != 0) { /* * We put ourselves on the sleep queue and start our * timeout before calling sleep_signal_check(), as we could * stop there, and a wakeup or a SIGCONT (or both) could * occur while we were stopped. A SIGCONT would cause * us to be marked as SSLEEP without resuming us, thus * we must be ready for sleep when sleep_signal_check() is * called. * If the wakeup happens while we're stopped, p->p_wchan * will be NULL upon return from sleep_signal_check(). In * that case we need to unwind immediately. */ atomic_setbits_int(&p->p_flag, P_SINTR); if ((error = sleep_signal_check()) != 0) { p->p_stat = SONPROC; sls->sls_catch = 0; do_sleep = 0; } else if (p->p_wchan == NULL) { sls->sls_catch = 0; do_sleep = 0; } } if (do_sleep) { p->p_stat = SSLEEP; p->p_ru.ru_nvcsw++; SCHED_ASSERT_LOCKED(); mi_switch(); } else { unsleep(p); } #ifdef DIAGNOSTIC if (p->p_stat != SONPROC) panic("sleep_finish !SONPROC"); #endif p->p_cpu->ci_schedstate.spc_curpriority = p->p_usrpri; SCHED_UNLOCK(sls->sls_s); /* * Even though this belongs to the signal handling part of sleep, * we need to clear it before the ktrace. */ atomic_clearbits_int(&p->p_flag, P_SINTR); if (sls->sls_timeout) { if (p->p_flag & P_TIMEOUT) { error1 = EWOULDBLOCK; } else { /* This can sleep. It must not use timeouts. */ timeout_del_barrier(&p->p_sleep_to); } atomic_clearbits_int(&p->p_flag, P_TIMEOUT); } /* Check if thread was woken up because of a unwind or signal */ if (sls->sls_catch != 0) error = sleep_signal_check(); /* Signal errors are higher priority than timeouts. */ if (error == 0 && error1 != 0) error = error1; return error; } /* * Check and handle signals and suspensions around a sleep cycle. */ int sleep_signal_check(void) { struct proc *p = curproc; struct sigctx ctx; int err, sig; if ((err = single_thread_check(p, 1)) != 0) return err; if ((sig = cursig(p, &ctx)) != 0) { if (ctx.sig_intr) return EINTR; else return ERESTART; } return 0; } int wakeup_proc(struct proc *p, const volatile void *chan) { int s, awakened = 0; SCHED_LOCK(s); if (p->p_wchan != NULL && ((chan == NULL) || (p->p_wchan == chan))) { awakened = 1; if (p->p_stat == SSLEEP) setrunnable(p); else unsleep(p); } SCHED_UNLOCK(s); return awakened; } /* * Implement timeout for tsleep. * If process hasn't been awakened (wchan non-zero), * set timeout flag and undo the sleep. If proc * is stopped, just unsleep so it will remain stopped. */ void endtsleep(void *arg) { struct proc *p = arg; int s; SCHED_LOCK(s); if (wakeup_proc(p, NULL)) atomic_setbits_int(&p->p_flag, P_TIMEOUT); SCHED_UNLOCK(s); } /* * Remove a process from its wait queue */ void unsleep(struct proc *p) { SCHED_ASSERT_LOCKED(); if (p->p_wchan != NULL) { TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_runq); p->p_wchan = NULL; TRACEPOINT(sched, wakeup, p->p_tid + THREAD_PID_OFFSET, p->p_p->ps_pid); } } /* * Make a number of processes sleeping on the specified identifier runnable. */ void wakeup_n(const volatile void *ident, int n) { struct slpque *qp; struct proc *p; struct proc *pnext; int s; SCHED_LOCK(s); qp = &slpque[LOOKUP(ident)]; for (p = TAILQ_FIRST(qp); p != NULL && n != 0; p = pnext) { pnext = TAILQ_NEXT(p, p_runq); /* * This happens if wakeup(9) is called after enqueuing * itself on the sleep queue and both `ident' collide. */ if (p == curproc) continue; #ifdef DIAGNOSTIC if (p->p_stat != SSLEEP && p->p_stat != SSTOP) panic("wakeup: p_stat is %d", (int)p->p_stat); #endif if (wakeup_proc(p, ident)) --n; } SCHED_UNLOCK(s); } /* * Make all processes sleeping on the specified identifier runnable. */ void wakeup(const volatile void *chan) { wakeup_n(chan, -1); } int sys_sched_yield(struct proc *p, void *v, register_t *retval) { struct proc *q; uint8_t newprio; int s; SCHED_LOCK(s); /* * If one of the threads of a multi-threaded process called * sched_yield(2), drop its priority to ensure its siblings * can make some progress. */ newprio = p->p_usrpri; TAILQ_FOREACH(q, &p->p_p->ps_threads, p_thr_link) newprio = max(newprio, q->p_runpri); setrunqueue(p->p_cpu, p, newprio); p->p_ru.ru_nvcsw++; mi_switch(); SCHED_UNLOCK(s); return (0); } int thrsleep_unlock(void *lock) { static _atomic_lock_t unlocked = _ATOMIC_LOCK_UNLOCKED; _atomic_lock_t *atomiclock = lock; if (!lock) return 0; return copyout(&unlocked, atomiclock, sizeof(unlocked)); } struct tslpentry { TAILQ_ENTRY(tslpentry) tslp_link; long tslp_ident; }; /* thrsleep queue shared between processes */ static struct tslpqueue thrsleep_queue = TAILQ_HEAD_INITIALIZER(thrsleep_queue); static struct rwlock thrsleep_lock = RWLOCK_INITIALIZER("thrsleeplk"); int thrsleep(struct proc *p, struct sys___thrsleep_args *v) { struct sys___thrsleep_args /* { syscallarg(const volatile void *) ident; syscallarg(clockid_t) clock_id; syscallarg(const struct timespec *) tp; syscallarg(void *) lock; syscallarg(const int *) abort; } */ *uap = v; long ident = (long)SCARG(uap, ident); struct tslpentry entry; struct tslpqueue *queue; struct rwlock *qlock; struct timespec *tsp = (struct timespec *)SCARG(uap, tp); void *lock = SCARG(uap, lock); uint64_t nsecs = INFSLP; int abort = 0, error; clockid_t clock_id = SCARG(uap, clock_id); if (ident == 0) return (EINVAL); if (tsp != NULL) { struct timespec now; if ((error = clock_gettime(p, clock_id, &now))) return (error); #ifdef KTRACE if (KTRPOINT(p, KTR_STRUCT)) ktrabstimespec(p, tsp); #endif if (timespeccmp(tsp, &now, <=)) { /* already passed: still do the unlock */ if ((error = thrsleep_unlock(lock))) return (error); return (EWOULDBLOCK); } timespecsub(tsp, &now, tsp); nsecs = MIN(TIMESPEC_TO_NSEC(tsp), MAXTSLP); } if (ident == -1) { queue = &thrsleep_queue; qlock = &thrsleep_lock; } else { queue = &p->p_p->ps_tslpqueue; qlock = &p->p_p->ps_lock; } /* Interlock with wakeup. */ entry.tslp_ident = ident; rw_enter_write(qlock); TAILQ_INSERT_TAIL(queue, &entry, tslp_link); rw_exit_write(qlock); error = thrsleep_unlock(lock); if (error == 0 && SCARG(uap, abort) != NULL) error = copyin(SCARG(uap, abort), &abort, sizeof(abort)); rw_enter_write(qlock); if (error != 0) goto out; if (abort != 0) { error = EINTR; goto out; } if (entry.tslp_ident != 0) { error = rwsleep_nsec(&entry, qlock, PWAIT|PCATCH, "thrsleep", nsecs); } out: if (entry.tslp_ident != 0) TAILQ_REMOVE(queue, &entry, tslp_link); rw_exit_write(qlock); if (error == ERESTART) error = ECANCELED; return (error); } int sys___thrsleep(struct proc *p, void *v, register_t *retval) { struct sys___thrsleep_args /* { syscallarg(const volatile void *) ident; syscallarg(clockid_t) clock_id; syscallarg(struct timespec *) tp; syscallarg(void *) lock; syscallarg(const int *) abort; } */ *uap = v; struct timespec ts; int error; if (SCARG(uap, tp) != NULL) { if ((error = copyin(SCARG(uap, tp), &ts, sizeof(ts)))) { *retval = error; return 0; } if (!timespecisvalid(&ts)) { *retval = EINVAL; return 0; } SCARG(uap, tp) = &ts; } *retval = thrsleep(p, uap); return 0; } int sys___thrwakeup(struct proc *p, void *v, register_t *retval) { struct sys___thrwakeup_args /* { syscallarg(const volatile void *) ident; syscallarg(int) n; } */ *uap = v; struct tslpentry *entry, *tmp; struct tslpqueue *queue; struct rwlock *qlock; long ident = (long)SCARG(uap, ident); int n = SCARG(uap, n); int found = 0; if (ident == 0) *retval = EINVAL; else { if (ident == -1) { queue = &thrsleep_queue; qlock = &thrsleep_lock; /* * Wake up all waiters with ident -1. This is needed * because ident -1 can be shared by multiple userspace * lock state machines concurrently. The implementation * has no way to direct the wakeup to a particular * state machine. */ n = 0; } else { queue = &p->p_p->ps_tslpqueue; qlock = &p->p_p->ps_lock; } rw_enter_write(qlock); TAILQ_FOREACH_SAFE(entry, queue, tslp_link, tmp) { if (entry->tslp_ident == ident) { TAILQ_REMOVE(queue, entry, tslp_link); entry->tslp_ident = 0; wakeup_one(entry); if (++found == n) break; } } rw_exit_write(qlock); if (ident == -1) *retval = 0; else *retval = found ? 0 : ESRCH; } return (0); } void refcnt_init(struct refcnt *r) { refcnt_init_trace(r, 0); } void refcnt_init_trace(struct refcnt *r, int idx) { r->r_traceidx = idx; atomic_store_int(&r->r_refs, 1); TRACEINDEX(refcnt, r->r_traceidx, r, 0, +1); } void refcnt_take(struct refcnt *r) { u_int refs; refs = atomic_inc_int_nv(&r->r_refs); KASSERT(refs != 0); TRACEINDEX(refcnt, r->r_traceidx, r, refs - 1, +1); (void)refs; } int refcnt_rele(struct refcnt *r) { u_int refs; membar_exit_before_atomic(); refs = atomic_dec_int_nv(&r->r_refs); KASSERT(refs != ~0); TRACEINDEX(refcnt, r->r_traceidx, r, refs + 1, -1); if (refs == 0) { membar_enter_after_atomic(); return (1); } return (0); } void refcnt_rele_wake(struct refcnt *r) { if (refcnt_rele(r)) wakeup_one(r); } void refcnt_finalize(struct refcnt *r, const char *wmesg) { struct sleep_state sls; u_int refs; membar_exit_before_atomic(); refs = atomic_dec_int_nv(&r->r_refs); KASSERT(refs != ~0); TRACEINDEX(refcnt, r->r_traceidx, r, refs + 1, -1); while (refs) { sleep_setup(&sls, r, PWAIT, wmesg, 0); refs = atomic_load_int(&r->r_refs); sleep_finish(&sls, refs); } TRACEINDEX(refcnt, r->r_traceidx, r, refs, 0); /* Order subsequent loads and stores after refs == 0 load. */ membar_sync(); } int refcnt_shared(struct refcnt *r) { u_int refs; refs = atomic_load_int(&r->r_refs); TRACEINDEX(refcnt, r->r_traceidx, r, refs, 0); return (refs > 1); } unsigned int refcnt_read(struct refcnt *r) { u_int refs; refs = atomic_load_int(&r->r_refs); TRACEINDEX(refcnt, r->r_traceidx, r, refs, 0); return (refs); } void cond_init(struct cond *c) { atomic_store_int(&c->c_wait, 1); } void cond_signal(struct cond *c) { atomic_store_int(&c->c_wait, 0); wakeup_one(c); } void cond_wait(struct cond *c, const char *wmesg) { struct sleep_state sls; unsigned int wait; wait = atomic_load_int(&c->c_wait); while (wait) { sleep_setup(&sls, c, PWAIT, wmesg, 0); wait = atomic_load_int(&c->c_wait); sleep_finish(&sls, wait); } }