/* $NetBSD: kern_lwp.c,v 1.127 2009/02/04 21:17:39 ad Exp $ */ /*- * Copyright (c) 2001, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Nathan J. Williams, and Andrew Doran. * * 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. */ /* * Overview * * Lightweight processes (LWPs) are the basic unit or thread of * execution within the kernel. The core state of an LWP is described * by "struct lwp", also known as lwp_t. * * Each LWP is contained within a process (described by "struct proc"), * Every process contains at least one LWP, but may contain more. The * process describes attributes shared among all of its LWPs such as a * private address space, global execution state (stopped, active, * zombie, ...), signal disposition and so on. On a multiprocessor * machine, multiple LWPs be executing concurrently in the kernel. * * Execution states * * At any given time, an LWP has overall state that is described by * lwp::l_stat. The states are broken into two sets below. The first * set is guaranteed to represent the absolute, current state of the * LWP: * * LSONPROC * * On processor: the LWP is executing on a CPU, either in the * kernel or in user space. * * LSRUN * * Runnable: the LWP is parked on a run queue, and may soon be * chosen to run by an idle processor, or by a processor that * has been asked to preempt a currently runnning but lower * priority LWP. If the LWP is not swapped in (LW_INMEM == 0) * then the LWP is not on a run queue, but may be soon. * * LSIDL * * Idle: the LWP has been created but has not yet executed, * or it has ceased executing a unit of work and is waiting * to be started again. * * LSSUSPENDED: * * Suspended: the LWP has had its execution suspended by * another LWP in the same process using the _lwp_suspend() * system call. User-level LWPs also enter the suspended * state when the system is shutting down. * * The second set represent a "statement of intent" on behalf of the * LWP. The LWP may in fact be executing on a processor, may be * sleeping or idle. It is expected to take the necessary action to * stop executing or become "running" again within a short timeframe. * The LP_RUNNING flag in lwp::l_pflag indicates that an LWP is running. * Importantly, it indicates that its state is tied to a CPU. * * LSZOMB: * * Dead or dying: the LWP has released most of its resources * and is: a) about to switch away into oblivion b) has already * switched away. When it switches away, its few remaining * resources can be collected. * * LSSLEEP: * * Sleeping: the LWP has entered itself onto a sleep queue, and * has switched away or will switch away shortly to allow other * LWPs to run on the CPU. * * LSSTOP: * * Stopped: the LWP has been stopped as a result of a job * control signal, or as a result of the ptrace() interface. * * Stopped LWPs may run briefly within the kernel to handle * signals that they receive, but will not return to user space * until their process' state is changed away from stopped. * * Single LWPs within a process can not be set stopped * selectively: all actions that can stop or continue LWPs * occur at the process level. * * State transitions * * Note that the LSSTOP state may only be set when returning to * user space in userret(), or when sleeping interruptably. The * LSSUSPENDED state may only be set in userret(). Before setting * those states, we try to ensure that the LWPs will release all * locks that they hold, and at a minimum try to ensure that the * LWP can be set runnable again by a signal. * * LWPs may transition states in the following ways: * * RUN -------> ONPROC ONPROC -----> RUN * > STOPPED > SLEEP * > SUSPENDED > STOPPED * > SUSPENDED * > ZOMB * * STOPPED ---> RUN SUSPENDED --> RUN * > SLEEP > SLEEP * * SLEEP -----> ONPROC IDL --------> RUN * > RUN > SUSPENDED * > STOPPED > STOPPED * > SUSPENDED * * Other state transitions are possible with kernel threads (eg * ONPROC -> IDL), but only happen under tightly controlled * circumstances the side effects are understood. * * Migration * * Migration of threads from one CPU to another could be performed * internally by the scheduler via sched_takecpu() or sched_catchlwp() * functions. The universal lwp_migrate() function should be used for * any other cases. Subsystems in the kernel must be aware that CPU * of LWP may change, while it is not locked. * * Locking * * The majority of fields in 'struct lwp' are covered by a single, * general spin lock pointed to by lwp::l_mutex. The locks covering * each field are documented in sys/lwp.h. * * State transitions must be made with the LWP's general lock held, * and may cause the LWP's lock pointer to change. Manipulation of * the general lock is not performed directly, but through calls to * lwp_lock(), lwp_relock() and similar. * * States and their associated locks: * * LSONPROC, LSZOMB: * * Always covered by spc_lwplock, which protects running LWPs. * This is a per-CPU lock. * * LSIDL, LSRUN: * * Always covered by spc_mutex, which protects the run queues. * This is a per-CPU lock. * * LSSLEEP: * * Covered by a lock associated with the sleep queue that the * LWP resides on. * * LSSTOP, LSSUSPENDED: * * If the LWP was previously sleeping (l_wchan != NULL), then * l_mutex references the sleep queue lock. If the LWP was * runnable or on the CPU when halted, or has been removed from * the sleep queue since halted, then the lock is spc_lwplock. * * The lock order is as follows: * * spc::spc_lwplock -> * sleeptab::st_mutex -> * tschain_t::tc_mutex -> * spc::spc_mutex * * Each process has an scheduler state lock (proc::p_lock), and a * number of counters on LWPs and their states: p_nzlwps, p_nrlwps, and * so on. When an LWP is to be entered into or removed from one of the * following states, p_lock must be held and the process wide counters * adjusted: * * LSIDL, LSZOMB, LSSTOP, LSSUSPENDED * * Note that an LWP is considered running or likely to run soon if in * one of the following states. This affects the value of p_nrlwps: * * LSRUN, LSONPROC, LSSLEEP * * p_lock does not need to be held when transitioning among these * three states. */ #include __KERNEL_RCSID(0, "$NetBSD: kern_lwp.c,v 1.127 2009/02/04 21:17:39 ad Exp $"); #include "opt_ddb.h" #include "opt_lockdebug.h" #include "opt_sa.h" #define _LWP_API_PRIVATE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct lwplist alllwp = LIST_HEAD_INITIALIZER(alllwp); POOL_INIT(lwp_uc_pool, sizeof(ucontext_t), 0, 0, 0, "lwpucpl", &pool_allocator_nointr, IPL_NONE); static pool_cache_t lwp_cache; static specificdata_domain_t lwp_specificdata_domain; void lwpinit(void) { lwp_specificdata_domain = specificdata_domain_create(); KASSERT(lwp_specificdata_domain != NULL); lwp_sys_init(); lwp_cache = pool_cache_init(sizeof(lwp_t), MIN_LWP_ALIGNMENT, 0, 0, "lwppl", NULL, IPL_NONE, NULL, NULL, NULL); } /* * Set an suspended. * * Must be called with p_lock held, and the LWP locked. Will unlock the * LWP before return. */ int lwp_suspend(struct lwp *curl, struct lwp *t) { int error; KASSERT(mutex_owned(t->l_proc->p_lock)); KASSERT(lwp_locked(t, NULL)); KASSERT(curl != t || curl->l_stat == LSONPROC); /* * If the current LWP has been told to exit, we must not suspend anyone * else or deadlock could occur. We won't return to userspace. */ if ((curl->l_flag & (LW_WEXIT | LW_WCORE)) != 0) { lwp_unlock(t); return (EDEADLK); } error = 0; switch (t->l_stat) { case LSRUN: case LSONPROC: t->l_flag |= LW_WSUSPEND; lwp_need_userret(t); lwp_unlock(t); break; case LSSLEEP: t->l_flag |= LW_WSUSPEND; /* * Kick the LWP and try to get it to the kernel boundary * so that it will release any locks that it holds. * setrunnable() will release the lock. */ if ((t->l_flag & LW_SINTR) != 0) setrunnable(t); else lwp_unlock(t); break; case LSSUSPENDED: lwp_unlock(t); break; case LSSTOP: t->l_flag |= LW_WSUSPEND; setrunnable(t); break; case LSIDL: case LSZOMB: error = EINTR; /* It's what Solaris does..... */ lwp_unlock(t); break; } return (error); } /* * Restart a suspended LWP. * * Must be called with p_lock held, and the LWP locked. Will unlock the * LWP before return. */ void lwp_continue(struct lwp *l) { KASSERT(mutex_owned(l->l_proc->p_lock)); KASSERT(lwp_locked(l, NULL)); /* If rebooting or not suspended, then just bail out. */ if ((l->l_flag & LW_WREBOOT) != 0) { lwp_unlock(l); return; } l->l_flag &= ~LW_WSUSPEND; if (l->l_stat != LSSUSPENDED) { lwp_unlock(l); return; } /* setrunnable() will release the lock. */ setrunnable(l); } /* * Wait for an LWP within the current process to exit. If 'lid' is * non-zero, we are waiting for a specific LWP. * * Must be called with p->p_lock held. */ int lwp_wait1(struct lwp *l, lwpid_t lid, lwpid_t *departed, int flags) { struct proc *p = l->l_proc; struct lwp *l2; int nfound, error; lwpid_t curlid; bool exiting; KASSERT(mutex_owned(p->p_lock)); p->p_nlwpwait++; l->l_waitingfor = lid; curlid = l->l_lid; exiting = ((flags & LWPWAIT_EXITCONTROL) != 0); for (;;) { /* * Avoid a race between exit1() and sigexit(): if the * process is dumping core, then we need to bail out: call * into lwp_userret() where we will be suspended until the * deed is done. */ if ((p->p_sflag & PS_WCORE) != 0) { mutex_exit(p->p_lock); lwp_userret(l); #ifdef DIAGNOSTIC panic("lwp_wait1"); #endif /* NOTREACHED */ } /* * First off, drain any detached LWP that is waiting to be * reaped. */ while ((l2 = p->p_zomblwp) != NULL) { p->p_zomblwp = NULL; lwp_free(l2, false, false);/* releases proc mutex */ mutex_enter(p->p_lock); } /* * Now look for an LWP to collect. If the whole process is * exiting, count detached LWPs as eligible to be collected, * but don't drain them here. */ nfound = 0; error = 0; LIST_FOREACH(l2, &p->p_lwps, l_sibling) { /* * If a specific wait and the target is waiting on * us, then avoid deadlock. This also traps LWPs * that try to wait on themselves. * * Note that this does not handle more complicated * cycles, like: t1 -> t2 -> t3 -> t1. The process * can still be killed so it is not a major problem. */ if (l2->l_lid == lid && l2->l_waitingfor == curlid) { error = EDEADLK; break; } if (l2 == l) continue; if ((l2->l_prflag & LPR_DETACHED) != 0) { nfound += exiting; continue; } if (lid != 0) { if (l2->l_lid != lid) continue; /* * Mark this LWP as the first waiter, if there * is no other. */ if (l2->l_waiter == 0) l2->l_waiter = curlid; } else if (l2->l_waiter != 0) { /* * It already has a waiter - so don't * collect it. If the waiter doesn't * grab it we'll get another chance * later. */ nfound++; continue; } nfound++; /* No need to lock the LWP in order to see LSZOMB. */ if (l2->l_stat != LSZOMB) continue; /* * We're no longer waiting. Reset the "first waiter" * pointer on the target, in case it was us. */ l->l_waitingfor = 0; l2->l_waiter = 0; p->p_nlwpwait--; if (departed) *departed = l2->l_lid; sched_lwp_collect(l2); /* lwp_free() releases the proc lock. */ lwp_free(l2, false, false); mutex_enter(p->p_lock); return 0; } if (error != 0) break; if (nfound == 0) { error = ESRCH; break; } /* * The kernel is careful to ensure that it can not deadlock * when exiting - just keep waiting. */ if (exiting) { KASSERT(p->p_nlwps > 1); cv_wait(&p->p_lwpcv, p->p_lock); continue; } /* * If all other LWPs are waiting for exits or suspends * and the supply of zombies and potential zombies is * exhausted, then we are about to deadlock. * * If the process is exiting (and this LWP is not the one * that is coordinating the exit) then bail out now. */ if ((p->p_sflag & PS_WEXIT) != 0 || p->p_nrlwps + p->p_nzlwps - p->p_ndlwps <= p->p_nlwpwait) { error = EDEADLK; break; } /* * Sit around and wait for something to happen. We'll be * awoken if any of the conditions examined change: if an * LWP exits, is collected, or is detached. */ if ((error = cv_wait_sig(&p->p_lwpcv, p->p_lock)) != 0) break; } /* * We didn't find any LWPs to collect, we may have received a * signal, or some other condition has caused us to bail out. * * If waiting on a specific LWP, clear the waiters marker: some * other LWP may want it. Then, kick all the remaining waiters * so that they can re-check for zombies and for deadlock. */ if (lid != 0) { LIST_FOREACH(l2, &p->p_lwps, l_sibling) { if (l2->l_lid == lid) { if (l2->l_waiter == curlid) l2->l_waiter = 0; break; } } } p->p_nlwpwait--; l->l_waitingfor = 0; cv_broadcast(&p->p_lwpcv); return error; } /* * Create a new LWP within process 'p2', using LWP 'l1' as a template. * The new LWP is created in state LSIDL and must be set running, * suspended, or stopped by the caller. */ int lwp_create(lwp_t *l1, proc_t *p2, vaddr_t uaddr, bool inmem, int flags, void *stack, size_t stacksize, void (*func)(void *), void *arg, lwp_t **rnewlwpp, int sclass) { struct lwp *l2, *isfree; turnstile_t *ts; KASSERT(l1 == curlwp || l1->l_proc == &proc0); /* * First off, reap any detached LWP waiting to be collected. * We can re-use its LWP structure and turnstile. */ isfree = NULL; if (p2->p_zomblwp != NULL) { mutex_enter(p2->p_lock); if ((isfree = p2->p_zomblwp) != NULL) { p2->p_zomblwp = NULL; lwp_free(isfree, true, false);/* releases proc mutex */ } else mutex_exit(p2->p_lock); } if (isfree == NULL) { l2 = pool_cache_get(lwp_cache, PR_WAITOK); memset(l2, 0, sizeof(*l2)); l2->l_ts = pool_cache_get(turnstile_cache, PR_WAITOK); SLIST_INIT(&l2->l_pi_lenders); } else { l2 = isfree; ts = l2->l_ts; KASSERT(l2->l_inheritedprio == -1); KASSERT(SLIST_EMPTY(&l2->l_pi_lenders)); memset(l2, 0, sizeof(*l2)); l2->l_ts = ts; } l2->l_stat = LSIDL; l2->l_proc = p2; l2->l_refcnt = 1; l2->l_class = sclass; /* * If vfork(), we want the LWP to run fast and on the same CPU * as its parent, so that it can reuse the VM context and cache * footprint on the local CPU. */ l2->l_kpriority = ((flags & LWP_VFORK) ? true : false); l2->l_kpribase = PRI_KERNEL; l2->l_priority = l1->l_priority; l2->l_inheritedprio = -1; l2->l_flag = inmem ? LW_INMEM : 0; l2->l_pflag = LP_MPSAFE; l2->l_fd = p2->p_fd; TAILQ_INIT(&l2->l_ld_locks); if (p2->p_flag & PK_SYSTEM) { /* Mark it as a system LWP and not a candidate for swapping */ l2->l_flag |= LW_SYSTEM; } kpreempt_disable(); l2->l_mutex = l1->l_cpu->ci_schedstate.spc_mutex; l2->l_cpu = l1->l_cpu; kpreempt_enable(); lwp_initspecific(l2); sched_lwp_fork(l1, l2); lwp_update_creds(l2); callout_init(&l2->l_timeout_ch, CALLOUT_MPSAFE); callout_setfunc(&l2->l_timeout_ch, sleepq_timeout, l2); mutex_init(&l2->l_swaplock, MUTEX_DEFAULT, IPL_NONE); cv_init(&l2->l_sigcv, "sigwait"); l2->l_syncobj = &sched_syncobj; if (rnewlwpp != NULL) *rnewlwpp = l2; l2->l_addr = UAREA_TO_USER(uaddr); uvm_lwp_fork(l1, l2, stack, stacksize, func, (arg != NULL) ? arg : l2); mutex_enter(p2->p_lock); if ((flags & LWP_DETACHED) != 0) { l2->l_prflag = LPR_DETACHED; p2->p_ndlwps++; } else l2->l_prflag = 0; l2->l_sigmask = l1->l_sigmask; CIRCLEQ_INIT(&l2->l_sigpend.sp_info); sigemptyset(&l2->l_sigpend.sp_set); p2->p_nlwpid++; if (p2->p_nlwpid == 0) p2->p_nlwpid++; l2->l_lid = p2->p_nlwpid; LIST_INSERT_HEAD(&p2->p_lwps, l2, l_sibling); p2->p_nlwps++; mutex_exit(p2->p_lock); mutex_enter(proc_lock); LIST_INSERT_HEAD(&alllwp, l2, l_list); mutex_exit(proc_lock); if ((p2->p_flag & PK_SYSTEM) == 0) { /* Locking is needed, since LWP is in the list of all LWPs */ lwp_lock(l2); /* Inherit a processor-set */ l2->l_psid = l1->l_psid; /* Inherit an affinity */ if (l1->l_flag & LW_AFFINITY) { proc_t *p = l1->l_proc; mutex_enter(p->p_lock); if (l1->l_flag & LW_AFFINITY) { kcpuset_use(l1->l_affinity); l2->l_affinity = l1->l_affinity; l2->l_flag |= LW_AFFINITY; } mutex_exit(p->p_lock); } /* Look for a CPU to start */ l2->l_cpu = sched_takecpu(l2); lwp_unlock_to(l2, l2->l_cpu->ci_schedstate.spc_mutex); } SYSCALL_TIME_LWP_INIT(l2); if (p2->p_emul->e_lwp_fork) (*p2->p_emul->e_lwp_fork)(l1, l2); return (0); } /* * Called by MD code when a new LWP begins execution. Must be called * with the previous LWP locked (so at splsched), or if there is no * previous LWP, at splsched. */ void lwp_startup(struct lwp *prev, struct lwp *new) { KASSERT(kpreempt_disabled()); if (prev != NULL) { /* * Normalize the count of the spin-mutexes, it was * increased in mi_switch(). Unmark the state of * context switch - it is finished for previous LWP. */ curcpu()->ci_mtx_count++; membar_exit(); prev->l_ctxswtch = 0; } KPREEMPT_DISABLE(new); spl0(); pmap_activate(new); LOCKDEBUG_BARRIER(NULL, 0); KPREEMPT_ENABLE(new); if ((new->l_pflag & LP_MPSAFE) == 0) { KERNEL_LOCK(1, new); } } /* * Exit an LWP. */ void lwp_exit(struct lwp *l) { struct proc *p = l->l_proc; struct lwp *l2; bool current; current = (l == curlwp); KASSERT(current || (l->l_stat == LSIDL && l->l_target_cpu == NULL)); /* * Verify that we hold no locks other than the kernel lock. */ LOCKDEBUG_BARRIER(&kernel_lock, 0); /* * If we are the last live LWP in a process, we need to exit the * entire process. We do so with an exit status of zero, because * it's a "controlled" exit, and because that's what Solaris does. * * We are not quite a zombie yet, but for accounting purposes we * must increment the count of zombies here. * * Note: the last LWP's specificdata will be deleted here. */ mutex_enter(p->p_lock); if (p->p_nlwps - p->p_nzlwps == 1) { KASSERT(current == true); /* XXXSMP kernel_lock not held */ exit1(l, 0); /* NOTREACHED */ } p->p_nzlwps++; mutex_exit(p->p_lock); if (p->p_emul->e_lwp_exit) (*p->p_emul->e_lwp_exit)(l); /* Delete the specificdata while it's still safe to sleep. */ specificdata_fini(lwp_specificdata_domain, &l->l_specdataref); /* * Release our cached credentials. */ kauth_cred_free(l->l_cred); callout_destroy(&l->l_timeout_ch); /* * While we can still block, mark the LWP as unswappable to * prevent conflicts with the with the swapper. */ if (current) uvm_lwp_hold(l); /* * Remove the LWP from the global list. */ mutex_enter(proc_lock); LIST_REMOVE(l, l_list); mutex_exit(proc_lock); /* * Get rid of all references to the LWP that others (e.g. procfs) * may have, and mark the LWP as a zombie. If the LWP is detached, * mark it waiting for collection in the proc structure. Note that * before we can do that, we need to free any other dead, deatched * LWP waiting to meet its maker. */ mutex_enter(p->p_lock); lwp_drainrefs(l); if ((l->l_prflag & LPR_DETACHED) != 0) { while ((l2 = p->p_zomblwp) != NULL) { p->p_zomblwp = NULL; lwp_free(l2, false, false);/* releases proc mutex */ mutex_enter(p->p_lock); l->l_refcnt++; lwp_drainrefs(l); } p->p_zomblwp = l; } /* * If we find a pending signal for the process and we have been * asked to check for signals, then we loose: arrange to have * all other LWPs in the process check for signals. */ if ((l->l_flag & LW_PENDSIG) != 0 && firstsig(&p->p_sigpend.sp_set) != 0) { LIST_FOREACH(l2, &p->p_lwps, l_sibling) { lwp_lock(l2); l2->l_flag |= LW_PENDSIG; lwp_unlock(l2); } } lwp_lock(l); l->l_stat = LSZOMB; if (l->l_name != NULL) strcpy(l->l_name, "(zombie)"); if (l->l_flag & LW_AFFINITY) l->l_flag &= ~LW_AFFINITY; lwp_unlock(l); p->p_nrlwps--; cv_broadcast(&p->p_lwpcv); if (l->l_lwpctl != NULL) l->l_lwpctl->lc_curcpu = LWPCTL_CPU_EXITED; mutex_exit(p->p_lock); /* Safe without lock since LWP is in zombie state */ if (l->l_affinity) { kcpuset_unuse(l->l_affinity, NULL); l->l_affinity = NULL; } /* * We can no longer block. At this point, lwp_free() may already * be gunning for us. On a multi-CPU system, we may be off p_lwps. * * Free MD LWP resources. */ #ifndef __NO_CPU_LWP_FREE cpu_lwp_free(l, 0); #endif if (current) { pmap_deactivate(l); /* * Release the kernel lock, and switch away into * oblivion. */ #ifdef notyet /* XXXSMP hold in lwp_userret() */ KERNEL_UNLOCK_LAST(l); #else KERNEL_UNLOCK_ALL(l, NULL); #endif lwp_exit_switchaway(l); } } /* * Free a dead LWP's remaining resources. * * XXXLWP limits. */ void lwp_free(struct lwp *l, bool recycle, bool last) { struct proc *p = l->l_proc; struct rusage *ru; ksiginfoq_t kq; KASSERT(l != curlwp); /* * If this was not the last LWP in the process, then adjust * counters and unlock. */ if (!last) { /* * Add the LWP's run time to the process' base value. * This needs to co-incide with coming off p_lwps. */ bintime_add(&p->p_rtime, &l->l_rtime); p->p_pctcpu += l->l_pctcpu; ru = &p->p_stats->p_ru; ruadd(ru, &l->l_ru); ru->ru_nvcsw += (l->l_ncsw - l->l_nivcsw); ru->ru_nivcsw += l->l_nivcsw; LIST_REMOVE(l, l_sibling); p->p_nlwps--; p->p_nzlwps--; if ((l->l_prflag & LPR_DETACHED) != 0) p->p_ndlwps--; /* * Have any LWPs sleeping in lwp_wait() recheck for * deadlock. */ cv_broadcast(&p->p_lwpcv); mutex_exit(p->p_lock); } #ifdef MULTIPROCESSOR /* * In the unlikely event that the LWP is still on the CPU, * then spin until it has switched away. We need to release * all locks to avoid deadlock against interrupt handlers on * the target CPU. */ if ((l->l_pflag & LP_RUNNING) != 0 || l->l_cpu->ci_curlwp == l) { int count; (void)count; /* XXXgcc */ KERNEL_UNLOCK_ALL(curlwp, &count); while ((l->l_pflag & LP_RUNNING) != 0 || l->l_cpu->ci_curlwp == l) SPINLOCK_BACKOFF_HOOK; KERNEL_LOCK(count, curlwp); } #endif /* * Destroy the LWP's remaining signal information. */ ksiginfo_queue_init(&kq); sigclear(&l->l_sigpend, NULL, &kq); ksiginfo_queue_drain(&kq); cv_destroy(&l->l_sigcv); mutex_destroy(&l->l_swaplock); /* * Free the LWP's turnstile and the LWP structure itself unless the * caller wants to recycle them. Also, free the scheduler specific * data. * * We can't return turnstile0 to the pool (it didn't come from it), * so if it comes up just drop it quietly and move on. * * We don't recycle the VM resources at this time. */ if (l->l_lwpctl != NULL) lwp_ctl_free(l); if (!recycle && l->l_ts != &turnstile0) pool_cache_put(turnstile_cache, l->l_ts); if (l->l_name != NULL) kmem_free(l->l_name, MAXCOMLEN); #ifndef __NO_CPU_LWP_FREE cpu_lwp_free2(l); #endif KASSERT((l->l_flag & LW_INMEM) != 0); uvm_lwp_exit(l); KASSERT(SLIST_EMPTY(&l->l_pi_lenders)); KASSERT(l->l_inheritedprio == -1); if (!recycle) pool_cache_put(lwp_cache, l); } /* * Migrate the LWP to the another CPU. Unlocks the LWP. */ void lwp_migrate(lwp_t *l, struct cpu_info *tci) { struct schedstate_percpu *tspc; int lstat = l->l_stat; KASSERT(lwp_locked(l, NULL)); KASSERT(tci != NULL); /* If LWP is still on the CPU, it must be handled like LSONPROC */ if ((l->l_pflag & LP_RUNNING) != 0) { lstat = LSONPROC; } /* * The destination CPU could be changed while previous migration * was not finished. */ if (l->l_target_cpu != NULL) { l->l_target_cpu = tci; lwp_unlock(l); return; } /* Nothing to do if trying to migrate to the same CPU */ if (l->l_cpu == tci) { lwp_unlock(l); return; } KASSERT(l->l_target_cpu == NULL); tspc = &tci->ci_schedstate; switch (lstat) { case LSRUN: if (l->l_flag & LW_INMEM) { l->l_target_cpu = tci; lwp_unlock(l); return; } case LSIDL: l->l_cpu = tci; lwp_unlock_to(l, tspc->spc_mutex); return; case LSSLEEP: l->l_cpu = tci; break; case LSSTOP: case LSSUSPENDED: l->l_cpu = tci; if (l->l_wchan == NULL) { lwp_unlock_to(l, tspc->spc_lwplock); return; } break; case LSONPROC: l->l_target_cpu = tci; spc_lock(l->l_cpu); cpu_need_resched(l->l_cpu, RESCHED_KPREEMPT); spc_unlock(l->l_cpu); break; } lwp_unlock(l); } /* * Find the LWP in the process. Arguments may be zero, in such case, * the calling process and first LWP in the list will be used. * On success - returns proc locked. */ struct lwp * lwp_find2(pid_t pid, lwpid_t lid) { proc_t *p; lwp_t *l; /* Find the process */ p = (pid == 0) ? curlwp->l_proc : p_find(pid, PFIND_UNLOCK_FAIL); if (p == NULL) return NULL; mutex_enter(p->p_lock); if (pid != 0) { /* Case of p_find */ mutex_exit(proc_lock); } /* Find the thread */ l = (lid == 0) ? LIST_FIRST(&p->p_lwps) : lwp_find(p, lid); if (l == NULL) { mutex_exit(p->p_lock); } return l; } /* * Look up a live LWP within the speicifed process, and return it locked. * * Must be called with p->p_lock held. */ struct lwp * lwp_find(struct proc *p, int id) { struct lwp *l; KASSERT(mutex_owned(p->p_lock)); LIST_FOREACH(l, &p->p_lwps, l_sibling) { if (l->l_lid == id) break; } /* * No need to lock - all of these conditions will * be visible with the process level mutex held. */ if (l != NULL && (l->l_stat == LSIDL || l->l_stat == LSZOMB)) l = NULL; return l; } /* * Update an LWP's cached credentials to mirror the process' master copy. * * This happens early in the syscall path, on user trap, and on LWP * creation. A long-running LWP can also voluntarily choose to update * it's credentials by calling this routine. This may be called from * LWP_CACHE_CREDS(), which checks l->l_cred != p->p_cred beforehand. */ void lwp_update_creds(struct lwp *l) { kauth_cred_t oc; struct proc *p; p = l->l_proc; oc = l->l_cred; mutex_enter(p->p_lock); kauth_cred_hold(p->p_cred); l->l_cred = p->p_cred; l->l_prflag &= ~LPR_CRMOD; mutex_exit(p->p_lock); if (oc != NULL) kauth_cred_free(oc); } /* * Verify that an LWP is locked, and optionally verify that the lock matches * one we specify. */ int lwp_locked(struct lwp *l, kmutex_t *mtx) { kmutex_t *cur = l->l_mutex; return mutex_owned(cur) && (mtx == cur || mtx == NULL); } /* * Lock an LWP. */ kmutex_t * lwp_lock_retry(struct lwp *l, kmutex_t *old) { /* * XXXgcc ignoring kmutex_t * volatile on i386 * * gcc version 4.1.2 20061021 prerelease (NetBSD nb1 20061021) */ #if 1 while (l->l_mutex != old) { #else for (;;) { #endif mutex_spin_exit(old); old = l->l_mutex; mutex_spin_enter(old); /* * mutex_enter() will have posted a read barrier. Re-test * l->l_mutex. If it has changed, we need to try again. */ #if 1 } #else } while (__predict_false(l->l_mutex != old)); #endif return old; } /* * Lend a new mutex to an LWP. The old mutex must be held. */ void lwp_setlock(struct lwp *l, kmutex_t *new) { KASSERT(mutex_owned(l->l_mutex)); membar_exit(); l->l_mutex = new; } /* * Lend a new mutex to an LWP, and release the old mutex. The old mutex * must be held. */ void lwp_unlock_to(struct lwp *l, kmutex_t *new) { kmutex_t *old; KASSERT(mutex_owned(l->l_mutex)); old = l->l_mutex; membar_exit(); l->l_mutex = new; mutex_spin_exit(old); } /* * Acquire a new mutex, and donate it to an LWP. The LWP must already be * locked. */ void lwp_relock(struct lwp *l, kmutex_t *new) { kmutex_t *old; KASSERT(mutex_owned(l->l_mutex)); old = l->l_mutex; if (old != new) { mutex_spin_enter(new); l->l_mutex = new; mutex_spin_exit(old); } } int lwp_trylock(struct lwp *l) { kmutex_t *old; for (;;) { if (!mutex_tryenter(old = l->l_mutex)) return 0; if (__predict_true(l->l_mutex == old)) return 1; mutex_spin_exit(old); } } u_int lwp_unsleep(lwp_t *l, bool cleanup) { KASSERT(mutex_owned(l->l_mutex)); return (*l->l_syncobj->sobj_unsleep)(l, cleanup); } /* * Handle exceptions for mi_userret(). Called if a member of LW_USERRET is * set. */ void lwp_userret(struct lwp *l) { struct proc *p; void (*hook)(void); int sig; KASSERT(l == curlwp); KASSERT(l->l_stat == LSONPROC); p = l->l_proc; #ifndef __HAVE_FAST_SOFTINTS /* Run pending soft interrupts. */ if (l->l_cpu->ci_data.cpu_softints != 0) softint_overlay(); #endif #ifdef KERN_SA /* Generate UNBLOCKED upcall if needed */ if (l->l_flag & LW_SA_BLOCKING) { sa_unblock_userret(l); /* NOTREACHED */ } #endif /* * It should be safe to do this read unlocked on a multiprocessor * system.. * * LW_SA_UPCALL will be handled after the while() loop, so don't * consider it now. */ while ((l->l_flag & (LW_USERRET & ~(LW_SA_UPCALL))) != 0) { /* * Process pending signals first, unless the process * is dumping core or exiting, where we will instead * enter the LW_WSUSPEND case below. */ if ((l->l_flag & (LW_PENDSIG | LW_WCORE | LW_WEXIT)) == LW_PENDSIG) { mutex_enter(p->p_lock); while ((sig = issignal(l)) != 0) postsig(sig); mutex_exit(p->p_lock); } /* * Core-dump or suspend pending. * * In case of core dump, suspend ourselves, so that the * kernel stack and therefore the userland registers saved * in the trapframe are around for coredump() to write them * out. We issue a wakeup on p->p_lwpcv so that sigexit() * will write the core file out once all other LWPs are * suspended. */ if ((l->l_flag & LW_WSUSPEND) != 0) { mutex_enter(p->p_lock); p->p_nrlwps--; cv_broadcast(&p->p_lwpcv); lwp_lock(l); l->l_stat = LSSUSPENDED; lwp_unlock(l); mutex_exit(p->p_lock); lwp_lock(l); mi_switch(l); } /* Process is exiting. */ if ((l->l_flag & LW_WEXIT) != 0) { lwp_exit(l); KASSERT(0); /* NOTREACHED */ } /* Call userret hook; used by Linux emulation. */ if ((l->l_flag & LW_WUSERRET) != 0) { lwp_lock(l); l->l_flag &= ~LW_WUSERRET; lwp_unlock(l); hook = p->p_userret; p->p_userret = NULL; (*hook)(); } } #ifdef KERN_SA /* * Timer events are handled specially. We only try once to deliver * pending timer upcalls; if if fails, we can try again on the next * loop around. If we need to re-enter lwp_userret(), MD code will * bounce us back here through the trap path after we return. */ if (p->p_timerpend) timerupcall(l); if (l->l_flag & LW_SA_UPCALL) sa_upcall_userret(l); #endif /* KERN_SA */ } /* * Force an LWP to enter the kernel, to take a trip through lwp_userret(). */ void lwp_need_userret(struct lwp *l) { KASSERT(lwp_locked(l, NULL)); /* * Since the tests in lwp_userret() are done unlocked, make sure * that the condition will be seen before forcing the LWP to enter * kernel mode. */ membar_producer(); cpu_signotify(l); } /* * Add one reference to an LWP. This will prevent the LWP from * exiting, thus keep the lwp structure and PCB around to inspect. */ void lwp_addref(struct lwp *l) { KASSERT(mutex_owned(l->l_proc->p_lock)); KASSERT(l->l_stat != LSZOMB); KASSERT(l->l_refcnt != 0); l->l_refcnt++; } /* * Remove one reference to an LWP. If this is the last reference, * then we must finalize the LWP's death. */ void lwp_delref(struct lwp *l) { struct proc *p = l->l_proc; mutex_enter(p->p_lock); KASSERT(l->l_stat != LSZOMB); KASSERT(l->l_refcnt > 0); if (--l->l_refcnt == 0) cv_broadcast(&p->p_lwpcv); mutex_exit(p->p_lock); } /* * Drain all references to the current LWP. */ void lwp_drainrefs(struct lwp *l) { struct proc *p = l->l_proc; KASSERT(mutex_owned(p->p_lock)); KASSERT(l->l_refcnt != 0); l->l_refcnt--; while (l->l_refcnt != 0) cv_wait(&p->p_lwpcv, p->p_lock); } /* * Return true if the specified LWP is 'alive'. Only p->p_lock need * be held. */ bool lwp_alive(lwp_t *l) { KASSERT(mutex_owned(l->l_proc->p_lock)); switch (l->l_stat) { case LSSLEEP: case LSRUN: case LSONPROC: case LSSTOP: case LSSUSPENDED: return true; default: return false; } } /* * Return first live LWP in the process. */ lwp_t * lwp_find_first(proc_t *p) { lwp_t *l; KASSERT(mutex_owned(p->p_lock)); LIST_FOREACH(l, &p->p_lwps, l_sibling) { if (lwp_alive(l)) { return l; } } return NULL; } /* * lwp_specific_key_create -- * Create a key for subsystem lwp-specific data. */ int lwp_specific_key_create(specificdata_key_t *keyp, specificdata_dtor_t dtor) { return (specificdata_key_create(lwp_specificdata_domain, keyp, dtor)); } /* * lwp_specific_key_delete -- * Delete a key for subsystem lwp-specific data. */ void lwp_specific_key_delete(specificdata_key_t key) { specificdata_key_delete(lwp_specificdata_domain, key); } /* * lwp_initspecific -- * Initialize an LWP's specificdata container. */ void lwp_initspecific(struct lwp *l) { int error; error = specificdata_init(lwp_specificdata_domain, &l->l_specdataref); KASSERT(error == 0); } /* * lwp_finispecific -- * Finalize an LWP's specificdata container. */ void lwp_finispecific(struct lwp *l) { specificdata_fini(lwp_specificdata_domain, &l->l_specdataref); } /* * lwp_getspecific -- * Return lwp-specific data corresponding to the specified key. * * Note: LWP specific data is NOT INTERLOCKED. An LWP should access * only its OWN SPECIFIC DATA. If it is necessary to access another * LWP's specifc data, care must be taken to ensure that doing so * would not cause internal data structure inconsistency (i.e. caller * can guarantee that the target LWP is not inside an lwp_getspecific() * or lwp_setspecific() call). */ void * lwp_getspecific(specificdata_key_t key) { return (specificdata_getspecific_unlocked(lwp_specificdata_domain, &curlwp->l_specdataref, key)); } void * _lwp_getspecific_by_lwp(struct lwp *l, specificdata_key_t key) { return (specificdata_getspecific_unlocked(lwp_specificdata_domain, &l->l_specdataref, key)); } /* * lwp_setspecific -- * Set lwp-specific data corresponding to the specified key. */ void lwp_setspecific(specificdata_key_t key, void *data) { specificdata_setspecific(lwp_specificdata_domain, &curlwp->l_specdataref, key, data); } /* * Allocate a new lwpctl structure for a user LWP. */ int lwp_ctl_alloc(vaddr_t *uaddr) { lcproc_t *lp; u_int bit, i, offset; struct uvm_object *uao; int error; lcpage_t *lcp; proc_t *p; lwp_t *l; l = curlwp; p = l->l_proc; if (l->l_lcpage != NULL) { lcp = l->l_lcpage; *uaddr = lcp->lcp_uaddr + (vaddr_t)l->l_lwpctl - lcp->lcp_kaddr; return (EINVAL); } /* First time around, allocate header structure for the process. */ if ((lp = p->p_lwpctl) == NULL) { lp = kmem_alloc(sizeof(*lp), KM_SLEEP); mutex_init(&lp->lp_lock, MUTEX_DEFAULT, IPL_NONE); lp->lp_uao = NULL; TAILQ_INIT(&lp->lp_pages); mutex_enter(p->p_lock); if (p->p_lwpctl == NULL) { p->p_lwpctl = lp; mutex_exit(p->p_lock); } else { mutex_exit(p->p_lock); mutex_destroy(&lp->lp_lock); kmem_free(lp, sizeof(*lp)); lp = p->p_lwpctl; } } /* * Set up an anonymous memory region to hold the shared pages. * Map them into the process' address space. The user vmspace * gets the first reference on the UAO. */ mutex_enter(&lp->lp_lock); if (lp->lp_uao == NULL) { lp->lp_uao = uao_create(LWPCTL_UAREA_SZ, 0); lp->lp_cur = 0; lp->lp_max = LWPCTL_UAREA_SZ; lp->lp_uva = p->p_emul->e_vm_default_addr(p, (vaddr_t)p->p_vmspace->vm_daddr, LWPCTL_UAREA_SZ); error = uvm_map(&p->p_vmspace->vm_map, &lp->lp_uva, LWPCTL_UAREA_SZ, lp->lp_uao, 0, 0, UVM_MAPFLAG(UVM_PROT_RW, UVM_PROT_RW, UVM_INH_NONE, UVM_ADV_NORMAL, 0)); if (error != 0) { uao_detach(lp->lp_uao); lp->lp_uao = NULL; mutex_exit(&lp->lp_lock); return error; } } /* Get a free block and allocate for this LWP. */ TAILQ_FOREACH(lcp, &lp->lp_pages, lcp_chain) { if (lcp->lcp_nfree != 0) break; } if (lcp == NULL) { /* Nothing available - try to set up a free page. */ if (lp->lp_cur == lp->lp_max) { mutex_exit(&lp->lp_lock); return ENOMEM; } lcp = kmem_alloc(LWPCTL_LCPAGE_SZ, KM_SLEEP); if (lcp == NULL) { mutex_exit(&lp->lp_lock); return ENOMEM; } /* * Wire the next page down in kernel space. Since this * is a new mapping, we must add a reference. */ uao = lp->lp_uao; (*uao->pgops->pgo_reference)(uao); lcp->lcp_kaddr = vm_map_min(kernel_map); error = uvm_map(kernel_map, &lcp->lcp_kaddr, PAGE_SIZE, uao, lp->lp_cur, PAGE_SIZE, UVM_MAPFLAG(UVM_PROT_RW, UVM_PROT_RW, UVM_INH_NONE, UVM_ADV_RANDOM, 0)); if (error != 0) { mutex_exit(&lp->lp_lock); kmem_free(lcp, LWPCTL_LCPAGE_SZ); (*uao->pgops->pgo_detach)(uao); return error; } error = uvm_map_pageable(kernel_map, lcp->lcp_kaddr, lcp->lcp_kaddr + PAGE_SIZE, FALSE, 0); if (error != 0) { mutex_exit(&lp->lp_lock); uvm_unmap(kernel_map, lcp->lcp_kaddr, lcp->lcp_kaddr + PAGE_SIZE); kmem_free(lcp, LWPCTL_LCPAGE_SZ); return error; } /* Prepare the page descriptor and link into the list. */ lcp->lcp_uaddr = lp->lp_uva + lp->lp_cur; lp->lp_cur += PAGE_SIZE; lcp->lcp_nfree = LWPCTL_PER_PAGE; lcp->lcp_rotor = 0; memset(lcp->lcp_bitmap, 0xff, LWPCTL_BITMAP_SZ); TAILQ_INSERT_HEAD(&lp->lp_pages, lcp, lcp_chain); } for (i = lcp->lcp_rotor; lcp->lcp_bitmap[i] == 0;) { if (++i >= LWPCTL_BITMAP_ENTRIES) i = 0; } bit = ffs(lcp->lcp_bitmap[i]) - 1; lcp->lcp_bitmap[i] ^= (1 << bit); lcp->lcp_rotor = i; lcp->lcp_nfree--; l->l_lcpage = lcp; offset = (i << 5) + bit; l->l_lwpctl = (lwpctl_t *)lcp->lcp_kaddr + offset; *uaddr = lcp->lcp_uaddr + offset * sizeof(lwpctl_t); mutex_exit(&lp->lp_lock); KPREEMPT_DISABLE(l); l->l_lwpctl->lc_curcpu = (int)curcpu()->ci_data.cpu_index; KPREEMPT_ENABLE(l); return 0; } /* * Free an lwpctl structure back to the per-process list. */ void lwp_ctl_free(lwp_t *l) { lcproc_t *lp; lcpage_t *lcp; u_int map, offset; lp = l->l_proc->p_lwpctl; KASSERT(lp != NULL); lcp = l->l_lcpage; offset = (u_int)((lwpctl_t *)l->l_lwpctl - (lwpctl_t *)lcp->lcp_kaddr); KASSERT(offset < LWPCTL_PER_PAGE); mutex_enter(&lp->lp_lock); lcp->lcp_nfree++; map = offset >> 5; lcp->lcp_bitmap[map] |= (1 << (offset & 31)); if (lcp->lcp_bitmap[lcp->lcp_rotor] == 0) lcp->lcp_rotor = map; if (TAILQ_FIRST(&lp->lp_pages)->lcp_nfree == 0) { TAILQ_REMOVE(&lp->lp_pages, lcp, lcp_chain); TAILQ_INSERT_HEAD(&lp->lp_pages, lcp, lcp_chain); } mutex_exit(&lp->lp_lock); } /* * Process is exiting; tear down lwpctl state. This can only be safely * called by the last LWP in the process. */ void lwp_ctl_exit(void) { lcpage_t *lcp, *next; lcproc_t *lp; proc_t *p; lwp_t *l; l = curlwp; l->l_lwpctl = NULL; l->l_lcpage = NULL; p = l->l_proc; lp = p->p_lwpctl; KASSERT(lp != NULL); KASSERT(p->p_nlwps == 1); for (lcp = TAILQ_FIRST(&lp->lp_pages); lcp != NULL; lcp = next) { next = TAILQ_NEXT(lcp, lcp_chain); uvm_unmap(kernel_map, lcp->lcp_kaddr, lcp->lcp_kaddr + PAGE_SIZE); kmem_free(lcp, LWPCTL_LCPAGE_SZ); } if (lp->lp_uao != NULL) { uvm_unmap(&p->p_vmspace->vm_map, lp->lp_uva, lp->lp_uva + LWPCTL_UAREA_SZ); } mutex_destroy(&lp->lp_lock); kmem_free(lp, sizeof(*lp)); p->p_lwpctl = NULL; } #if defined(DDB) void lwp_whatis(uintptr_t addr, void (*pr)(const char *, ...)) { lwp_t *l; LIST_FOREACH(l, &alllwp, l_list) { uintptr_t stack = (uintptr_t)KSTACK_LOWEST_ADDR(l); if (addr < stack || stack + KSTACK_SIZE <= addr) { continue; } (*pr)("%p is %p+%zu, LWP %p's stack\n", (void *)addr, (void *)stack, (size_t)(addr - stack), l); } } #endif /* defined(DDB) */