/* $NetBSD: kern_synch.c,v 1.251 2008/07/25 00:48:59 uwe Exp $ */ /*- * Copyright (c) 1999, 2000, 2004, 2006, 2007, 2008 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, * NASA Ames Research Center, by Charles M. Hannum, Andrew Doran and * Daniel Sieger. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /*- * 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 8.9 (Berkeley) 5/19/95 */ #include __KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.251 2008/07/25 00:48:59 uwe Exp $"); #include "opt_kstack.h" #include "opt_perfctrs.h" #define __MUTEX_PRIVATE #include #include #include #include #if defined(PERFCTRS) #include #endif #include #include #include #include #include #include #include #include #include #include #include #include #include static u_int sched_unsleep(struct lwp *, bool); static void sched_changepri(struct lwp *, pri_t); static void sched_lendpri(struct lwp *, pri_t); static void resched_cpu(struct lwp *); syncobj_t sleep_syncobj = { SOBJ_SLEEPQ_SORTED, sleepq_unsleep, sleepq_changepri, sleepq_lendpri, syncobj_noowner, }; syncobj_t sched_syncobj = { SOBJ_SLEEPQ_SORTED, sched_unsleep, sched_changepri, sched_lendpri, syncobj_noowner, }; callout_t sched_pstats_ch; unsigned sched_pstats_ticks; kcondvar_t lbolt; /* once a second sleep address */ /* Preemption event counters */ static struct evcnt kpreempt_ev_crit; static struct evcnt kpreempt_ev_klock; static struct evcnt kpreempt_ev_ipl; static struct evcnt kpreempt_ev_immed; /* * 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. */ int safepri; void sched_init(void) { cv_init(&lbolt, "lbolt"); callout_init(&sched_pstats_ch, CALLOUT_MPSAFE); callout_setfunc(&sched_pstats_ch, sched_pstats, NULL); evcnt_attach_dynamic(&kpreempt_ev_crit, EVCNT_TYPE_MISC, NULL, "kpreempt", "defer: critical section"); evcnt_attach_dynamic(&kpreempt_ev_klock, EVCNT_TYPE_MISC, NULL, "kpreempt", "defer: kernel_lock"); evcnt_attach_dynamic(&kpreempt_ev_ipl, EVCNT_TYPE_MISC, NULL, "kpreempt", "defer: IPL"); evcnt_attach_dynamic(&kpreempt_ev_immed, EVCNT_TYPE_MISC, NULL, "kpreempt", "immediate"); sched_pstats(NULL); } /* * OBSOLETE INTERFACE * * 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). * * The interlock is held until we are on a sleep queue. The interlock will * be locked before returning back to the caller unless the PNORELOCK flag * is specified, in which case the interlock will always be unlocked upon * return. */ int ltsleep(wchan_t ident, pri_t priority, const char *wmesg, int timo, volatile struct simplelock *interlock) { struct lwp *l = curlwp; sleepq_t *sq; kmutex_t *mp; int error; KASSERT((l->l_pflag & LP_INTR) == 0); if (sleepq_dontsleep(l)) { (void)sleepq_abort(NULL, 0); if ((priority & PNORELOCK) != 0) simple_unlock(interlock); return 0; } l->l_kpriority = true; sq = sleeptab_lookup(&sleeptab, ident, &mp); sleepq_enter(sq, l, mp); sleepq_enqueue(sq, ident, wmesg, &sleep_syncobj); if (interlock != NULL) { KASSERT(simple_lock_held(interlock)); simple_unlock(interlock); } error = sleepq_block(timo, priority & PCATCH); if (interlock != NULL && (priority & PNORELOCK) == 0) simple_lock(interlock); return error; } int mtsleep(wchan_t ident, pri_t priority, const char *wmesg, int timo, kmutex_t *mtx) { struct lwp *l = curlwp; sleepq_t *sq; kmutex_t *mp; int error; KASSERT((l->l_pflag & LP_INTR) == 0); if (sleepq_dontsleep(l)) { (void)sleepq_abort(mtx, (priority & PNORELOCK) != 0); return 0; } l->l_kpriority = true; sq = sleeptab_lookup(&sleeptab, ident, &mp); sleepq_enter(sq, l, mp); sleepq_enqueue(sq, ident, wmesg, &sleep_syncobj); mutex_exit(mtx); error = sleepq_block(timo, priority & PCATCH); if ((priority & PNORELOCK) == 0) mutex_enter(mtx); return error; } /* * General sleep call for situations where a wake-up is not expected. */ int kpause(const char *wmesg, bool intr, int timo, kmutex_t *mtx) { struct lwp *l = curlwp; kmutex_t *mp; sleepq_t *sq; int error; if (sleepq_dontsleep(l)) return sleepq_abort(NULL, 0); if (mtx != NULL) mutex_exit(mtx); l->l_kpriority = true; sq = sleeptab_lookup(&sleeptab, l, &mp); sleepq_enter(sq, l, mp); sleepq_enqueue(sq, l, wmesg, &sleep_syncobj); error = sleepq_block(timo, intr); if (mtx != NULL) mutex_enter(mtx); return error; } /* * OBSOLETE INTERFACE * * Make all processes sleeping on the specified identifier runnable. */ void wakeup(wchan_t ident) { sleepq_t *sq; kmutex_t *mp; if (cold) return; sq = sleeptab_lookup(&sleeptab, ident, &mp); sleepq_wake(sq, ident, (u_int)-1, mp); } /* * OBSOLETE INTERFACE * * Make the highest priority process first in line on the specified * identifier runnable. */ void wakeup_one(wchan_t ident) { sleepq_t *sq; kmutex_t *mp; if (cold) return; sq = sleeptab_lookup(&sleeptab, ident, &mp); sleepq_wake(sq, ident, 1, mp); } /* * General yield call. Puts the current process back on its run queue and * performs a voluntary context switch. Should only be called when the * current process explicitly requests it (eg sched_yield(2)). */ void yield(void) { struct lwp *l = curlwp; KERNEL_UNLOCK_ALL(l, &l->l_biglocks); lwp_lock(l); KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_lwplock)); KASSERT(l->l_stat == LSONPROC); l->l_kpriority = false; (void)mi_switch(l); KERNEL_LOCK(l->l_biglocks, l); } /* * General preemption call. Puts the current process back on its run queue * and performs an involuntary context switch. */ void preempt(void) { struct lwp *l = curlwp; KERNEL_UNLOCK_ALL(l, &l->l_biglocks); lwp_lock(l); KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_lwplock)); KASSERT(l->l_stat == LSONPROC); l->l_kpriority = false; l->l_nivcsw++; (void)mi_switch(l); KERNEL_LOCK(l->l_biglocks, l); } /* * Handle a request made by another agent to preempt the current LWP * in-kernel. Usually called when l_dopreempt may be non-zero. * * Character addresses for lockstat only. */ static char in_critical_section; static char kernel_lock_held; static char spl_raised; static char is_softint; bool kpreempt(uintptr_t where) { uintptr_t failed; lwp_t *l; int s, dop; l = curlwp; failed = 0; while ((dop = l->l_dopreempt) != 0) { if (l->l_stat != LSONPROC) { /* * About to block (or die), let it happen. * Doesn't really count as "preemption has * been blocked", since we're going to * context switch. */ l->l_dopreempt = 0; return true; } if (__predict_false((l->l_flag & LW_IDLE) != 0)) { /* Can't preempt idle loop, don't count as failure. */ l->l_dopreempt = 0; return true; } if (__predict_false(l->l_nopreempt != 0)) { /* LWP holds preemption disabled, explicitly. */ if ((dop & DOPREEMPT_COUNTED) == 0) { kpreempt_ev_crit.ev_count++; } failed = (uintptr_t)&in_critical_section; break; } if (__predict_false((l->l_pflag & LP_INTR) != 0)) { /* Can't preempt soft interrupts yet. */ l->l_dopreempt = 0; failed = (uintptr_t)&is_softint; break; } s = splsched(); if (__predict_false(l->l_blcnt != 0 || curcpu()->ci_biglock_wanted != NULL)) { /* Hold or want kernel_lock, code is not MT safe. */ splx(s); if ((dop & DOPREEMPT_COUNTED) == 0) { kpreempt_ev_klock.ev_count++; } failed = (uintptr_t)&kernel_lock_held; break; } if (__predict_false(!cpu_kpreempt_enter(where, s))) { /* * It may be that the IPL is too high. * kpreempt_enter() can schedule an * interrupt to retry later. */ splx(s); if ((dop & DOPREEMPT_COUNTED) == 0) { kpreempt_ev_ipl.ev_count++; } failed = (uintptr_t)&spl_raised; break; } /* Do it! */ if (__predict_true((dop & DOPREEMPT_COUNTED) == 0)) { kpreempt_ev_immed.ev_count++; } lwp_lock(l); mi_switch(l); l->l_nopreempt++; splx(s); /* Take care of any MD cleanup. */ cpu_kpreempt_exit(where); l->l_nopreempt--; } /* Record preemption failure for reporting via lockstat. */ if (__predict_false(failed)) { int lsflag = 0; atomic_or_uint(&l->l_dopreempt, DOPREEMPT_COUNTED); LOCKSTAT_ENTER(lsflag); /* Might recurse, make it atomic. */ if (__predict_false(lsflag)) { if (where == 0) { where = (uintptr_t)__builtin_return_address(0); } if (atomic_cas_ptr_ni((void *)&l->l_pfailaddr, NULL, (void *)where) == NULL) { LOCKSTAT_START_TIMER(lsflag, l->l_pfailtime); l->l_pfaillock = failed; } } LOCKSTAT_EXIT(lsflag); } return failed; } /* * Return true if preemption is explicitly disabled. */ bool kpreempt_disabled(void) { lwp_t *l; l = curlwp; return l->l_nopreempt != 0 || l->l_stat == LSZOMB || (l->l_flag & LW_IDLE) != 0 || cpu_kpreempt_disabled(); } /* * Disable kernel preemption. */ void kpreempt_disable(void) { KPREEMPT_DISABLE(curlwp); } /* * Reenable kernel preemption. */ void kpreempt_enable(void) { KPREEMPT_ENABLE(curlwp); } /* * Compute the amount of time during which the current lwp was running. * * - update l_rtime unless it's an idle lwp. */ void updatertime(lwp_t *l, const struct bintime *now) { if ((l->l_flag & LW_IDLE) != 0) return; /* rtime += now - stime */ bintime_add(&l->l_rtime, now); bintime_sub(&l->l_rtime, &l->l_stime); } /* * Select next LWP from the current CPU to run.. */ static inline lwp_t * nextlwp(struct cpu_info *ci, struct schedstate_percpu *spc) { lwp_t *newl; /* * Let sched_nextlwp() select the LWP to run the CPU next. * If no LWP is runnable, select the idle LWP. * * Note that spc_lwplock might not necessary be held, and * new thread would be unlocked after setting the LWP-lock. */ newl = sched_nextlwp(); if (newl != NULL) { sched_dequeue(newl); KASSERT(lwp_locked(newl, spc->spc_mutex)); newl->l_stat = LSONPROC; newl->l_cpu = ci; newl->l_pflag |= LP_RUNNING; lwp_setlock(newl, spc->spc_lwplock); } else { newl = ci->ci_data.cpu_idlelwp; newl->l_stat = LSONPROC; newl->l_pflag |= LP_RUNNING; } /* * Only clear want_resched if there are no pending (slow) * software interrupts. */ ci->ci_want_resched = ci->ci_data.cpu_softints; spc->spc_flags &= ~SPCF_SWITCHCLEAR; spc->spc_curpriority = lwp_eprio(newl); return newl; } /* * The machine independent parts of context switch. * * Returns 1 if another LWP was actually run. */ int mi_switch(lwp_t *l) { struct cpu_info *ci; struct schedstate_percpu *spc; struct lwp *newl; int retval, oldspl; struct bintime bt; bool returning; KASSERT(lwp_locked(l, NULL)); KASSERT(kpreempt_disabled()); LOCKDEBUG_BARRIER(l->l_mutex, 1); #ifdef KSTACK_CHECK_MAGIC kstack_check_magic(l); #endif binuptime(&bt); KASSERT(l->l_cpu == curcpu()); ci = l->l_cpu; spc = &ci->ci_schedstate; returning = false; newl = NULL; /* * If we have been asked to switch to a specific LWP, then there * is no need to inspect the run queues. If a soft interrupt is * blocking, then return to the interrupted thread without adjusting * VM context or its start time: neither have been changed in order * to take the interrupt. */ if (l->l_switchto != NULL) { if ((l->l_pflag & LP_INTR) != 0) { returning = true; softint_block(l); if ((l->l_pflag & LP_TIMEINTR) != 0) updatertime(l, &bt); } newl = l->l_switchto; l->l_switchto = NULL; } #ifndef __HAVE_FAST_SOFTINTS else if (ci->ci_data.cpu_softints != 0) { /* There are pending soft interrupts, so pick one. */ newl = softint_picklwp(); newl->l_stat = LSONPROC; newl->l_pflag |= LP_RUNNING; } #endif /* !__HAVE_FAST_SOFTINTS */ /* Count time spent in current system call */ if (!returning) { SYSCALL_TIME_SLEEP(l); /* * XXXSMP If we are using h/w performance counters, * save context. */ #if PERFCTRS if (PMC_ENABLED(l->l_proc)) { pmc_save_context(l->l_proc); } #endif updatertime(l, &bt); } /* Lock the runqueue */ KASSERT(l->l_stat != LSRUN); mutex_spin_enter(spc->spc_mutex); /* * If on the CPU and we have gotten this far, then we must yield. */ if (l->l_stat == LSONPROC && l != newl) { KASSERT(lwp_locked(l, spc->spc_lwplock)); if ((l->l_flag & LW_IDLE) == 0) { l->l_stat = LSRUN; lwp_setlock(l, spc->spc_mutex); sched_enqueue(l, true); /* Handle migration case */ KASSERT(spc->spc_migrating == NULL); if (l->l_target_cpu != NULL) { spc->spc_migrating = l; } } else l->l_stat = LSIDL; } /* Pick new LWP to run. */ if (newl == NULL) { newl = nextlwp(ci, spc); } /* Items that must be updated with the CPU locked. */ if (!returning) { /* Update the new LWP's start time. */ newl->l_stime = bt; /* * ci_curlwp changes when a fast soft interrupt occurs. * We use cpu_onproc to keep track of which kernel or * user thread is running 'underneath' the software * interrupt. This is important for time accounting, * itimers and forcing user threads to preempt (aston). */ ci->ci_data.cpu_onproc = newl; } /* * Preemption related tasks. Must be done with the current * CPU locked. */ cpu_did_resched(l); l->l_dopreempt = 0; if (__predict_false(l->l_pfailaddr != 0)) { LOCKSTAT_FLAG(lsflag); LOCKSTAT_ENTER(lsflag); LOCKSTAT_STOP_TIMER(lsflag, l->l_pfailtime); LOCKSTAT_EVENT_RA(lsflag, l->l_pfaillock, LB_NOPREEMPT|LB_SPIN, 1, l->l_pfailtime, l->l_pfailaddr); LOCKSTAT_EXIT(lsflag); l->l_pfailtime = 0; l->l_pfaillock = 0; l->l_pfailaddr = 0; } if (l != newl) { struct lwp *prevlwp; /* Release all locks, but leave the current LWP locked */ if (l->l_mutex == spc->spc_mutex) { /* * Drop spc_lwplock, if the current LWP has been moved * to the run queue (it is now locked by spc_mutex). */ mutex_spin_exit(spc->spc_lwplock); } else { /* * Otherwise, drop the spc_mutex, we are done with the * run queues. */ mutex_spin_exit(spc->spc_mutex); } /* * Mark that context switch is going to be perfomed * for this LWP, to protect it from being switched * to on another CPU. */ KASSERT(l->l_ctxswtch == 0); l->l_ctxswtch = 1; l->l_ncsw++; l->l_pflag &= ~LP_RUNNING; /* * Increase the count of spin-mutexes before the release * of the last lock - we must remain at IPL_SCHED during * the context switch. */ oldspl = MUTEX_SPIN_OLDSPL(ci); ci->ci_mtx_count--; lwp_unlock(l); /* Count the context switch on this CPU. */ ci->ci_data.cpu_nswtch++; /* Update status for lwpctl, if present. */ if (l->l_lwpctl != NULL) l->l_lwpctl->lc_curcpu = LWPCTL_CPU_NONE; /* * Save old VM context, unless a soft interrupt * handler is blocking. */ if (!returning) pmap_deactivate(l); /* * We may need to spin-wait for if 'newl' is still * context switching on another CPU. */ if (newl->l_ctxswtch != 0) { u_int count; count = SPINLOCK_BACKOFF_MIN; while (newl->l_ctxswtch) SPINLOCK_BACKOFF(count); } /* Switch to the new LWP.. */ prevlwp = cpu_switchto(l, newl, returning); ci = curcpu(); /* * Switched away - we have new curlwp. * Restore VM context and IPL. */ pmap_activate(l); if (prevlwp != NULL) { /* Normalize the count of the spin-mutexes */ ci->ci_mtx_count++; /* Unmark the state of context switch */ membar_exit(); prevlwp->l_ctxswtch = 0; } /* Update status for lwpctl, if present. */ if (l->l_lwpctl != NULL) { l->l_lwpctl->lc_curcpu = (int)cpu_index(ci); l->l_lwpctl->lc_pctr++; } KASSERT(l->l_cpu == ci); splx(oldspl); retval = 1; } else { /* Nothing to do - just unlock and return. */ mutex_spin_exit(spc->spc_mutex); lwp_unlock(l); retval = 0; } KASSERT(l == curlwp); KASSERT(l->l_stat == LSONPROC); /* * XXXSMP If we are using h/w performance counters, restore context. * XXXSMP preemption problem. */ #if PERFCTRS if (PMC_ENABLED(l->l_proc)) { pmc_restore_context(l->l_proc); } #endif SYSCALL_TIME_WAKEUP(l); LOCKDEBUG_BARRIER(NULL, 1); return retval; } /* * The machine independent parts of context switch to oblivion. * Does not return. Call with the LWP unlocked. */ void lwp_exit_switchaway(lwp_t *l) { struct cpu_info *ci; struct lwp *newl; struct bintime bt; ci = l->l_cpu; KASSERT(kpreempt_disabled()); KASSERT(l->l_stat == LSZOMB || l->l_stat == LSIDL); KASSERT(ci == curcpu()); LOCKDEBUG_BARRIER(NULL, 0); #ifdef KSTACK_CHECK_MAGIC kstack_check_magic(l); #endif /* Count time spent in current system call */ SYSCALL_TIME_SLEEP(l); binuptime(&bt); updatertime(l, &bt); /* Must stay at IPL_SCHED even after releasing run queue lock. */ (void)splsched(); /* * Let sched_nextlwp() select the LWP to run the CPU next. * If no LWP is runnable, select the idle LWP. * * Note that spc_lwplock might not necessary be held, and * new thread would be unlocked after setting the LWP-lock. */ spc_lock(ci); #ifndef __HAVE_FAST_SOFTINTS if (ci->ci_data.cpu_softints != 0) { /* There are pending soft interrupts, so pick one. */ newl = softint_picklwp(); newl->l_stat = LSONPROC; newl->l_pflag |= LP_RUNNING; } else #endif /* !__HAVE_FAST_SOFTINTS */ { newl = nextlwp(ci, &ci->ci_schedstate); } /* Update the new LWP's start time. */ newl->l_stime = bt; l->l_pflag &= ~LP_RUNNING; /* * ci_curlwp changes when a fast soft interrupt occurs. * We use cpu_onproc to keep track of which kernel or * user thread is running 'underneath' the software * interrupt. This is important for time accounting, * itimers and forcing user threads to preempt (aston). */ ci->ci_data.cpu_onproc = newl; /* * Preemption related tasks. Must be done with the current * CPU locked. */ cpu_did_resched(l); /* Unlock the run queue. */ spc_unlock(ci); /* Count the context switch on this CPU. */ ci->ci_data.cpu_nswtch++; /* Update status for lwpctl, if present. */ if (l->l_lwpctl != NULL) l->l_lwpctl->lc_curcpu = LWPCTL_CPU_EXITED; /* * We may need to spin-wait for if 'newl' is still * context switching on another CPU. */ if (newl->l_ctxswtch != 0) { u_int count; count = SPINLOCK_BACKOFF_MIN; while (newl->l_ctxswtch) SPINLOCK_BACKOFF(count); } /* Switch to the new LWP.. */ (void)cpu_switchto(NULL, newl, false); for (;;) continue; /* XXX: convince gcc about "noreturn" */ /* NOTREACHED */ } /* * Change process state to be runnable, placing it on the run queue if it is * in memory, and awakening the swapper if it isn't in memory. * * Call with the process and LWP locked. Will return with the LWP unlocked. */ void setrunnable(struct lwp *l) { struct proc *p = l->l_proc; struct cpu_info *ci; sigset_t *ss; KASSERT((l->l_flag & LW_IDLE) == 0); KASSERT(mutex_owned(p->p_lock)); KASSERT(lwp_locked(l, NULL)); KASSERT(l->l_mutex != l->l_cpu->ci_schedstate.spc_mutex); switch (l->l_stat) { case LSSTOP: /* * If we're being traced (possibly because someone attached us * while we were stopped), check for a signal from the debugger. */ if ((p->p_slflag & PSL_TRACED) != 0 && p->p_xstat != 0) { if ((sigprop[p->p_xstat] & SA_TOLWP) != 0) ss = &l->l_sigpend.sp_set; else ss = &p->p_sigpend.sp_set; sigaddset(ss, p->p_xstat); signotify(l); } p->p_nrlwps++; break; case LSSUSPENDED: l->l_flag &= ~LW_WSUSPEND; p->p_nrlwps++; cv_broadcast(&p->p_lwpcv); break; case LSSLEEP: KASSERT(l->l_wchan != NULL); break; default: panic("setrunnable: lwp %p state was %d", l, l->l_stat); } /* * If the LWP was sleeping interruptably, then it's OK to start it * again. If not, mark it as still sleeping. */ if (l->l_wchan != NULL) { l->l_stat = LSSLEEP; /* lwp_unsleep() will release the lock. */ lwp_unsleep(l, true); return; } /* * If the LWP is still on the CPU, mark it as LSONPROC. It may be * about to call mi_switch(), in which case it will yield. */ if ((l->l_pflag & LP_RUNNING) != 0) { l->l_stat = LSONPROC; l->l_slptime = 0; lwp_unlock(l); return; } /* * Look for a CPU to run. * Set the LWP runnable. */ ci = sched_takecpu(l); l->l_cpu = ci; spc_lock(ci); lwp_unlock_to(l, ci->ci_schedstate.spc_mutex); sched_setrunnable(l); l->l_stat = LSRUN; l->l_slptime = 0; /* * If thread is swapped out - wake the swapper to bring it back in. * Otherwise, enter it into a run queue. */ if (l->l_flag & LW_INMEM) { sched_enqueue(l, false); resched_cpu(l); lwp_unlock(l); } else { lwp_unlock(l); uvm_kick_scheduler(); } } /* * suspendsched: * * Convert all non-L_SYSTEM LSSLEEP or LSRUN LWPs to LSSUSPENDED. */ void suspendsched(void) { CPU_INFO_ITERATOR cii; struct cpu_info *ci; struct lwp *l; struct proc *p; /* * We do this by process in order not to violate the locking rules. */ mutex_enter(proc_lock); PROCLIST_FOREACH(p, &allproc) { if ((p->p_flag & PK_MARKER) != 0) continue; mutex_enter(p->p_lock); if ((p->p_flag & PK_SYSTEM) != 0) { mutex_exit(p->p_lock); continue; } p->p_stat = SSTOP; LIST_FOREACH(l, &p->p_lwps, l_sibling) { if (l == curlwp) continue; lwp_lock(l); /* * Set L_WREBOOT so that the LWP will suspend itself * when it tries to return to user mode. We want to * try and get to get as many LWPs as possible to * the user / kernel boundary, so that they will * release any locks that they hold. */ l->l_flag |= (LW_WREBOOT | LW_WSUSPEND); if (l->l_stat == LSSLEEP && (l->l_flag & LW_SINTR) != 0) { /* setrunnable() will release the lock. */ setrunnable(l); continue; } lwp_unlock(l); } mutex_exit(p->p_lock); } mutex_exit(proc_lock); /* * Kick all CPUs to make them preempt any LWPs running in user mode. * They'll trap into the kernel and suspend themselves in userret(). */ for (CPU_INFO_FOREACH(cii, ci)) { spc_lock(ci); cpu_need_resched(ci, RESCHED_IMMED); spc_unlock(ci); } } /* * sched_unsleep: * * The is called when the LWP has not been awoken normally but instead * interrupted: for example, if the sleep timed out. Because of this, * it's not a valid action for running or idle LWPs. */ static u_int sched_unsleep(struct lwp *l, bool cleanup) { lwp_unlock(l); panic("sched_unsleep"); } static void resched_cpu(struct lwp *l) { struct cpu_info *ci = ci = l->l_cpu; KASSERT(lwp_locked(l, NULL)); if (lwp_eprio(l) > ci->ci_schedstate.spc_curpriority) cpu_need_resched(ci, 0); } static void sched_changepri(struct lwp *l, pri_t pri) { KASSERT(lwp_locked(l, NULL)); if (l->l_stat == LSRUN && (l->l_flag & LW_INMEM) != 0) { KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_mutex)); sched_dequeue(l); l->l_priority = pri; sched_enqueue(l, false); } else { l->l_priority = pri; } resched_cpu(l); } static void sched_lendpri(struct lwp *l, pri_t pri) { KASSERT(lwp_locked(l, NULL)); if (l->l_stat == LSRUN && (l->l_flag & LW_INMEM) != 0) { KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_mutex)); sched_dequeue(l); l->l_inheritedprio = pri; sched_enqueue(l, false); } else { l->l_inheritedprio = pri; } resched_cpu(l); } struct lwp * syncobj_noowner(wchan_t wchan) { return NULL; } /* Decay 95% of proc::p_pctcpu in 60 seconds, ccpu = exp(-1/20) */ const fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* * sched_pstats: * * Update process statistics and check CPU resource allocation. * Call scheduler-specific hook to eventually adjust process/LWP * priorities. */ /* ARGSUSED */ void sched_pstats(void *arg) { const int clkhz = (stathz != 0 ? stathz : hz); struct rlimit *rlim; struct lwp *l; struct proc *p; long runtm; fixpt_t lpctcpu; u_int lcpticks; int sig; sched_pstats_ticks++; mutex_enter(proc_lock); PROCLIST_FOREACH(p, &allproc) { if (__predict_false((p->p_flag & PK_MARKER) != 0)) continue; /* * Increment time in/out of memory and sleep * time (if sleeping), ignore overflow. */ mutex_enter(p->p_lock); runtm = p->p_rtime.sec; LIST_FOREACH(l, &p->p_lwps, l_sibling) { if (__predict_false((l->l_flag & LW_IDLE) != 0)) continue; lwp_lock(l); runtm += l->l_rtime.sec; l->l_swtime++; sched_lwp_stats(l); lwp_unlock(l); l->l_pctcpu = (l->l_pctcpu * ccpu) >> FSHIFT; if (l->l_slptime != 0) continue; lpctcpu = l->l_pctcpu; lcpticks = atomic_swap_uint(&l->l_cpticks, 0); lpctcpu += ((FSCALE - ccpu) * (lcpticks * FSCALE / clkhz)) >> FSHIFT; l->l_pctcpu = lpctcpu; } /* Calculating p_pctcpu only for ps(1) */ p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; /* * Check if the process exceeds its CPU resource allocation. * If over max, kill it. */ rlim = &p->p_rlimit[RLIMIT_CPU]; sig = 0; if (__predict_false(runtm >= rlim->rlim_cur)) { if (runtm >= rlim->rlim_max) sig = SIGKILL; else { sig = SIGXCPU; if (rlim->rlim_cur < rlim->rlim_max) rlim->rlim_cur += 5; } } mutex_exit(p->p_lock); if (__predict_false(sig)) psignal(p, sig); } mutex_exit(proc_lock); uvm_meter(); cv_wakeup(&lbolt); callout_schedule(&sched_pstats_ch, hz); }