/*- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD * * Copyright (C) 2001 Julian Elischer . * All rights reserved. * * 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(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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. */ #include "opt_witness.h" #include "opt_hwpmc_hooks.h" #include __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef HWPMC_HOOKS #include #endif #include #include #include #include #include #include #include #include /* * Asserts below verify the stability of struct thread and struct proc * layout, as exposed by KBI to modules. On head, the KBI is allowed * to drift, change to the structures must be accompanied by the * assert update. * * On the stable branches after KBI freeze, conditions must not be * violated. Typically new fields are moved to the end of the * structures. */ #ifdef __amd64__ _Static_assert(offsetof(struct thread, td_flags) == 0x108, "struct thread KBI td_flags"); _Static_assert(offsetof(struct thread, td_pflags) == 0x114, "struct thread KBI td_pflags"); _Static_assert(offsetof(struct thread, td_frame) == 0x4b0, "struct thread KBI td_frame"); _Static_assert(offsetof(struct thread, td_emuldata) == 0x6c0, "struct thread KBI td_emuldata"); _Static_assert(offsetof(struct proc, p_flag) == 0xb8, "struct proc KBI p_flag"); _Static_assert(offsetof(struct proc, p_pid) == 0xc4, "struct proc KBI p_pid"); _Static_assert(offsetof(struct proc, p_filemon) == 0x3c8, "struct proc KBI p_filemon"); _Static_assert(offsetof(struct proc, p_comm) == 0x3e4, "struct proc KBI p_comm"); _Static_assert(offsetof(struct proc, p_emuldata) == 0x4c8, "struct proc KBI p_emuldata"); #endif #ifdef __i386__ _Static_assert(offsetof(struct thread, td_flags) == 0x9c, "struct thread KBI td_flags"); _Static_assert(offsetof(struct thread, td_pflags) == 0xa8, "struct thread KBI td_pflags"); _Static_assert(offsetof(struct thread, td_frame) == 0x30c, "struct thread KBI td_frame"); _Static_assert(offsetof(struct thread, td_emuldata) == 0x350, "struct thread KBI td_emuldata"); _Static_assert(offsetof(struct proc, p_flag) == 0x6c, "struct proc KBI p_flag"); _Static_assert(offsetof(struct proc, p_pid) == 0x78, "struct proc KBI p_pid"); _Static_assert(offsetof(struct proc, p_filemon) == 0x270, "struct proc KBI p_filemon"); _Static_assert(offsetof(struct proc, p_comm) == 0x288, "struct proc KBI p_comm"); _Static_assert(offsetof(struct proc, p_emuldata) == 0x314, "struct proc KBI p_emuldata"); #endif SDT_PROVIDER_DECLARE(proc); SDT_PROBE_DEFINE(proc, , , lwp__exit); /* * thread related storage. */ static uma_zone_t thread_zone; struct thread_domain_data { struct thread *tdd_zombies; int tdd_reapticks; } __aligned(CACHE_LINE_SIZE); static struct thread_domain_data thread_domain_data[MAXMEMDOM]; static struct task thread_reap_task; static struct callout thread_reap_callout; static void thread_zombie(struct thread *); static void thread_reap(void); static void thread_reap_all(void); static void thread_reap_task_cb(void *, int); static void thread_reap_callout_cb(void *); static int thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary); static void thread_free_batched(struct thread *td); static __exclusive_cache_line struct mtx tid_lock; static bitstr_t *tid_bitmap; static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); static int maxthread; SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN, &maxthread, 0, "Maximum number of threads"); static __exclusive_cache_line int nthreads; static LIST_HEAD(tidhashhead, thread) *tidhashtbl; static u_long tidhash; static u_long tidhashlock; static struct rwlock *tidhashtbl_lock; #define TIDHASH(tid) (&tidhashtbl[(tid) & tidhash]) #define TIDHASHLOCK(tid) (&tidhashtbl_lock[(tid) & tidhashlock]) EVENTHANDLER_LIST_DEFINE(thread_ctor); EVENTHANDLER_LIST_DEFINE(thread_dtor); EVENTHANDLER_LIST_DEFINE(thread_init); EVENTHANDLER_LIST_DEFINE(thread_fini); static bool thread_count_inc_try(void) { int nthreads_new; nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1; if (nthreads_new >= maxthread - 100) { if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 || nthreads_new >= maxthread) { atomic_subtract_int(&nthreads, 1); return (false); } } return (true); } static bool thread_count_inc(void) { static struct timeval lastfail; static int curfail; thread_reap(); if (thread_count_inc_try()) { return (true); } thread_reap_all(); if (thread_count_inc_try()) { return (true); } if (ppsratecheck(&lastfail, &curfail, 1)) { printf("maxthread limit exceeded by uid %u " "(pid %d); consider increasing kern.maxthread\n", curthread->td_ucred->cr_ruid, curproc->p_pid); } return (false); } static void thread_count_sub(int n) { atomic_subtract_int(&nthreads, n); } static void thread_count_dec(void) { thread_count_sub(1); } static lwpid_t tid_alloc(void) { static lwpid_t trytid; lwpid_t tid; mtx_lock(&tid_lock); /* * It is an invariant that the bitmap is big enough to hold maxthread * IDs. If we got to this point there has to be at least one free. */ if (trytid >= maxthread) trytid = 0; bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); if (tid == -1) { KASSERT(trytid != 0, ("unexpectedly ran out of IDs")); trytid = 0; bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); KASSERT(tid != -1, ("unexpectedly ran out of IDs")); } bit_set(tid_bitmap, tid); trytid = tid + 1; mtx_unlock(&tid_lock); return (tid + NO_PID); } static void tid_free_locked(lwpid_t rtid) { lwpid_t tid; mtx_assert(&tid_lock, MA_OWNED); KASSERT(rtid >= NO_PID, ("%s: invalid tid %d\n", __func__, rtid)); tid = rtid - NO_PID; KASSERT(bit_test(tid_bitmap, tid) != 0, ("thread ID %d not allocated\n", rtid)); bit_clear(tid_bitmap, tid); } static void tid_free(lwpid_t rtid) { mtx_lock(&tid_lock); tid_free_locked(rtid); mtx_unlock(&tid_lock); } static void tid_free_batch(lwpid_t *batch, int n) { int i; mtx_lock(&tid_lock); for (i = 0; i < n; i++) { tid_free_locked(batch[i]); } mtx_unlock(&tid_lock); } /* * Batching for thread reapping. */ struct tidbatch { lwpid_t tab[16]; int n; }; static void tidbatch_prep(struct tidbatch *tb) { tb->n = 0; } static void tidbatch_add(struct tidbatch *tb, struct thread *td) { KASSERT(tb->n < nitems(tb->tab), ("%s: count too high %d", __func__, tb->n)); tb->tab[tb->n] = td->td_tid; tb->n++; } static void tidbatch_process(struct tidbatch *tb) { KASSERT(tb->n <= nitems(tb->tab), ("%s: count too high %d", __func__, tb->n)); if (tb->n == nitems(tb->tab)) { tid_free_batch(tb->tab, tb->n); tb->n = 0; } } static void tidbatch_final(struct tidbatch *tb) { KASSERT(tb->n <= nitems(tb->tab), ("%s: count too high %d", __func__, tb->n)); if (tb->n != 0) { tid_free_batch(tb->tab, tb->n); } } /* * Prepare a thread for use. */ static int thread_ctor(void *mem, int size, void *arg, int flags) { struct thread *td; td = (struct thread *)mem; TD_SET_STATE(td, TDS_INACTIVE); td->td_lastcpu = td->td_oncpu = NOCPU; /* * Note that td_critnest begins life as 1 because the thread is not * running and is thereby implicitly waiting to be on the receiving * end of a context switch. */ td->td_critnest = 1; td->td_lend_user_pri = PRI_MAX; #ifdef AUDIT audit_thread_alloc(td); #endif #ifdef KDTRACE_HOOKS kdtrace_thread_ctor(td); #endif umtx_thread_alloc(td); MPASS(td->td_sel == NULL); return (0); } /* * Reclaim a thread after use. */ static void thread_dtor(void *mem, int size, void *arg) { struct thread *td; td = (struct thread *)mem; #ifdef INVARIANTS /* Verify that this thread is in a safe state to free. */ switch (TD_GET_STATE(td)) { case TDS_INHIBITED: case TDS_RUNNING: case TDS_CAN_RUN: case TDS_RUNQ: /* * We must never unlink a thread that is in one of * these states, because it is currently active. */ panic("bad state for thread unlinking"); /* NOTREACHED */ case TDS_INACTIVE: break; default: panic("bad thread state"); /* NOTREACHED */ } #endif #ifdef AUDIT audit_thread_free(td); #endif #ifdef KDTRACE_HOOKS kdtrace_thread_dtor(td); #endif /* Free all OSD associated to this thread. */ osd_thread_exit(td); ast_kclear(td); seltdfini(td); } /* * Initialize type-stable parts of a thread (when newly created). */ static int thread_init(void *mem, int size, int flags) { struct thread *td; td = (struct thread *)mem; td->td_allocdomain = vm_phys_domain(vtophys(td)); td->td_sleepqueue = sleepq_alloc(); td->td_turnstile = turnstile_alloc(); td->td_rlqe = NULL; EVENTHANDLER_DIRECT_INVOKE(thread_init, td); umtx_thread_init(td); td->td_kstack = 0; td->td_sel = NULL; return (0); } /* * Tear down type-stable parts of a thread (just before being discarded). */ static void thread_fini(void *mem, int size) { struct thread *td; td = (struct thread *)mem; EVENTHANDLER_DIRECT_INVOKE(thread_fini, td); rlqentry_free(td->td_rlqe); turnstile_free(td->td_turnstile); sleepq_free(td->td_sleepqueue); umtx_thread_fini(td); MPASS(td->td_sel == NULL); } /* * For a newly created process, * link up all the structures and its initial threads etc. * called from: * {arch}/{arch}/machdep.c {arch}_init(), init386() etc. * proc_dtor() (should go away) * proc_init() */ void proc_linkup0(struct proc *p, struct thread *td) { TAILQ_INIT(&p->p_threads); /* all threads in proc */ proc_linkup(p, td); } void proc_linkup(struct proc *p, struct thread *td) { sigqueue_init(&p->p_sigqueue, p); p->p_ksi = ksiginfo_alloc(1); if (p->p_ksi != NULL) { /* XXX p_ksi may be null if ksiginfo zone is not ready */ p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; } LIST_INIT(&p->p_mqnotifier); p->p_numthreads = 0; thread_link(td, p); } static void ast_suspend(struct thread *td, int tda __unused) { struct proc *p; p = td->td_proc; /* * We need to check to see if we have to exit or wait due to a * single threading requirement or some other STOP condition. */ PROC_LOCK(p); thread_suspend_check(0); PROC_UNLOCK(p); } extern int max_threads_per_proc; /* * Initialize global thread allocation resources. */ void threadinit(void) { u_long i; lwpid_t tid0; uint32_t flags; /* * Place an upper limit on threads which can be allocated. * * Note that other factors may make the de facto limit much lower. * * Platform limits are somewhat arbitrary but deemed "more than good * enough" for the foreseable future. */ if (maxthread == 0) { #ifdef _LP64 maxthread = MIN(maxproc * max_threads_per_proc, 1000000); #else maxthread = MIN(maxproc * max_threads_per_proc, 100000); #endif } mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK); /* * Handle thread0. */ thread_count_inc(); tid0 = tid_alloc(); if (tid0 != THREAD0_TID) panic("tid0 %d != %d\n", tid0, THREAD0_TID); flags = UMA_ZONE_NOFREE; #ifdef __aarch64__ /* * Force thread structures to be allocated from the direct map. * Otherwise, superpage promotions and demotions may temporarily * invalidate thread structure mappings. For most dynamically allocated * structures this is not a problem, but translation faults cannot be * handled without accessing curthread. */ flags |= UMA_ZONE_CONTIG; #endif thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), thread_ctor, thread_dtor, thread_init, thread_fini, 32 - 1, flags); tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); tidhashlock = (tidhash + 1) / 64; if (tidhashlock > 0) tidhashlock--; tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1), M_TIDHASH, M_WAITOK | M_ZERO); for (i = 0; i < tidhashlock + 1; i++) rw_init(&tidhashtbl_lock[i], "tidhash"); TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL); callout_init(&thread_reap_callout, 1); callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL); ast_register(TDA_SUSPEND, ASTR_ASTF_REQUIRED, 0, ast_suspend); } /* * Place an unused thread on the zombie list. */ void thread_zombie(struct thread *td) { struct thread_domain_data *tdd; struct thread *ztd; tdd = &thread_domain_data[td->td_allocdomain]; ztd = atomic_load_ptr(&tdd->tdd_zombies); for (;;) { td->td_zombie = ztd; if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies, (uintptr_t *)&ztd, (uintptr_t)td)) break; continue; } } /* * Release a thread that has exited after cpu_throw(). */ void thread_stash(struct thread *td) { atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); thread_zombie(td); } /* * Reap zombies from passed domain. */ static void thread_reap_domain(struct thread_domain_data *tdd) { struct thread *itd, *ntd; struct tidbatch tidbatch; struct credbatch credbatch; int tdcount; struct plimit *lim; int limcount; /* * Reading upfront is pessimal if followed by concurrent atomic_swap, * but most of the time the list is empty. */ if (tdd->tdd_zombies == NULL) return; itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies, (uintptr_t)NULL); if (itd == NULL) return; /* * Multiple CPUs can get here, the race is fine as ticks is only * advisory. */ tdd->tdd_reapticks = ticks; tidbatch_prep(&tidbatch); credbatch_prep(&credbatch); tdcount = 0; lim = NULL; limcount = 0; while (itd != NULL) { ntd = itd->td_zombie; EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd); tidbatch_add(&tidbatch, itd); credbatch_add(&credbatch, itd); MPASS(itd->td_limit != NULL); if (lim != itd->td_limit) { if (limcount != 0) { lim_freen(lim, limcount); limcount = 0; } } lim = itd->td_limit; limcount++; thread_free_batched(itd); tidbatch_process(&tidbatch); credbatch_process(&credbatch); tdcount++; if (tdcount == 32) { thread_count_sub(tdcount); tdcount = 0; } itd = ntd; } tidbatch_final(&tidbatch); credbatch_final(&credbatch); if (tdcount != 0) { thread_count_sub(tdcount); } MPASS(limcount != 0); lim_freen(lim, limcount); } /* * Reap zombies from all domains. */ static void thread_reap_all(void) { struct thread_domain_data *tdd; int i, domain; domain = PCPU_GET(domain); for (i = 0; i < vm_ndomains; i++) { tdd = &thread_domain_data[(i + domain) % vm_ndomains]; thread_reap_domain(tdd); } } /* * Reap zombies from local domain. */ static void thread_reap(void) { struct thread_domain_data *tdd; int domain; domain = PCPU_GET(domain); tdd = &thread_domain_data[domain]; thread_reap_domain(tdd); } static void thread_reap_task_cb(void *arg __unused, int pending __unused) { thread_reap_all(); } static void thread_reap_callout_cb(void *arg __unused) { struct thread_domain_data *tdd; int i, cticks, lticks; bool wantreap; wantreap = false; cticks = atomic_load_int(&ticks); for (i = 0; i < vm_ndomains; i++) { tdd = &thread_domain_data[i]; lticks = tdd->tdd_reapticks; if (tdd->tdd_zombies != NULL && (u_int)(cticks - lticks) > 5 * hz) { wantreap = true; break; } } if (wantreap) taskqueue_enqueue(taskqueue_thread, &thread_reap_task); callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL); } /* * Calling this function guarantees that any thread that exited before * the call is reaped when the function returns. By 'exited' we mean * a thread removed from the process linkage with thread_unlink(). * Practically this means that caller must lock/unlock corresponding * process lock before the call, to synchronize with thread_exit(). */ void thread_reap_barrier(void) { struct task *t; /* * First do context switches to each CPU to ensure that all * PCPU pc_deadthreads are moved to zombie list. */ quiesce_all_cpus("", PDROP); /* * Second, fire the task in the same thread as normal * thread_reap() is done, to serialize reaping. */ t = malloc(sizeof(*t), M_TEMP, M_WAITOK); TASK_INIT(t, 0, thread_reap_task_cb, t); taskqueue_enqueue(taskqueue_thread, t); taskqueue_drain(taskqueue_thread, t); free(t, M_TEMP); } /* * Allocate a thread. */ struct thread * thread_alloc(int pages) { struct thread *td; lwpid_t tid; if (!thread_count_inc()) { return (NULL); } tid = tid_alloc(); td = uma_zalloc(thread_zone, M_WAITOK); KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); if (!vm_thread_new(td, pages)) { uma_zfree(thread_zone, td); tid_free(tid); thread_count_dec(); return (NULL); } td->td_tid = tid; bzero(&td->td_sa.args, sizeof(td->td_sa.args)); kmsan_thread_alloc(td); cpu_thread_alloc(td); EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); return (td); } int thread_alloc_stack(struct thread *td, int pages) { KASSERT(td->td_kstack == 0, ("thread_alloc_stack called on a thread with kstack")); if (!vm_thread_new(td, pages)) return (0); cpu_thread_alloc(td); return (1); } /* * Deallocate a thread. */ static void thread_free_batched(struct thread *td) { lock_profile_thread_exit(td); if (td->td_cpuset) cpuset_rel(td->td_cpuset); td->td_cpuset = NULL; cpu_thread_free(td); if (td->td_kstack != 0) vm_thread_dispose(td); callout_drain(&td->td_slpcallout); /* * Freeing handled by the caller. */ td->td_tid = -1; kmsan_thread_free(td); uma_zfree(thread_zone, td); } void thread_free(struct thread *td) { lwpid_t tid; EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); tid = td->td_tid; thread_free_batched(td); tid_free(tid); thread_count_dec(); } void thread_cow_get_proc(struct thread *newtd, struct proc *p) { PROC_LOCK_ASSERT(p, MA_OWNED); newtd->td_realucred = crcowget(p->p_ucred); newtd->td_ucred = newtd->td_realucred; newtd->td_limit = lim_hold(p->p_limit); newtd->td_cowgen = p->p_cowgen; } void thread_cow_get(struct thread *newtd, struct thread *td) { MPASS(td->td_realucred == td->td_ucred); newtd->td_realucred = crcowget(td->td_realucred); newtd->td_ucred = newtd->td_realucred; newtd->td_limit = lim_hold(td->td_limit); newtd->td_cowgen = td->td_cowgen; } void thread_cow_free(struct thread *td) { if (td->td_realucred != NULL) crcowfree(td); if (td->td_limit != NULL) lim_free(td->td_limit); } void thread_cow_update(struct thread *td) { struct proc *p; struct ucred *oldcred; struct plimit *oldlimit; p = td->td_proc; PROC_LOCK(p); oldcred = crcowsync(); oldlimit = lim_cowsync(); td->td_cowgen = p->p_cowgen; PROC_UNLOCK(p); if (oldcred != NULL) crfree(oldcred); if (oldlimit != NULL) lim_free(oldlimit); } void thread_cow_synced(struct thread *td) { struct proc *p; p = td->td_proc; PROC_LOCK_ASSERT(p, MA_OWNED); MPASS(td->td_cowgen != p->p_cowgen); MPASS(td->td_ucred == p->p_ucred); MPASS(td->td_limit == p->p_limit); td->td_cowgen = p->p_cowgen; } /* * Discard the current thread and exit from its context. * Always called with scheduler locked. * * Because we can't free a thread while we're operating under its context, * push the current thread into our CPU's deadthread holder. This means * we needn't worry about someone else grabbing our context before we * do a cpu_throw(). */ void thread_exit(void) { uint64_t runtime, new_switchtime; struct thread *td; struct thread *td2; struct proc *p; int wakeup_swapper; td = curthread; p = td->td_proc; PROC_SLOCK_ASSERT(p, MA_OWNED); mtx_assert(&Giant, MA_NOTOWNED); PROC_LOCK_ASSERT(p, MA_OWNED); KASSERT(p != NULL, ("thread exiting without a process")); CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, (long)p->p_pid, td->td_name); SDT_PROBE0(proc, , , lwp__exit); KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); MPASS(td->td_realucred == td->td_ucred); /* * drop FPU & debug register state storage, or any other * architecture specific resources that * would not be on a new untouched process. */ cpu_thread_exit(td); /* * The last thread is left attached to the process * So that the whole bundle gets recycled. Skip * all this stuff if we never had threads. * EXIT clears all sign of other threads when * it goes to single threading, so the last thread always * takes the short path. */ if (p->p_flag & P_HADTHREADS) { if (p->p_numthreads > 1) { atomic_add_int(&td->td_proc->p_exitthreads, 1); thread_unlink(td); td2 = FIRST_THREAD_IN_PROC(p); sched_exit_thread(td2, td); /* * The test below is NOT true if we are the * sole exiting thread. P_STOPPED_SINGLE is unset * in exit1() after it is the only survivor. */ if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { if (p->p_numthreads == p->p_suspcount) { thread_lock(p->p_singlethread); wakeup_swapper = thread_unsuspend_one( p->p_singlethread, p, false); if (wakeup_swapper) kick_proc0(); } } PCPU_SET(deadthread, td); } else { /* * The last thread is exiting.. but not through exit() */ panic ("thread_exit: Last thread exiting on its own"); } } #ifdef HWPMC_HOOKS /* * If this thread is part of a process that is being tracked by hwpmc(4), * inform the module of the thread's impending exit. */ if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); #endif PROC_UNLOCK(p); PROC_STATLOCK(p); thread_lock(td); PROC_SUNLOCK(p); /* Do the same timestamp bookkeeping that mi_switch() would do. */ new_switchtime = cpu_ticks(); runtime = new_switchtime - PCPU_GET(switchtime); td->td_runtime += runtime; td->td_incruntime += runtime; PCPU_SET(switchtime, new_switchtime); PCPU_SET(switchticks, ticks); VM_CNT_INC(v_swtch); /* Save our resource usage in our process. */ td->td_ru.ru_nvcsw++; ruxagg_locked(p, td); rucollect(&p->p_ru, &td->td_ru); PROC_STATUNLOCK(p); TD_SET_STATE(td, TDS_INACTIVE); #ifdef WITNESS witness_thread_exit(td); #endif CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); sched_throw(td); panic("I'm a teapot!"); /* NOTREACHED */ } /* * Do any thread specific cleanups that may be needed in wait() * called with Giant, proc and schedlock not held. */ void thread_wait(struct proc *p) { struct thread *td; mtx_assert(&Giant, MA_NOTOWNED); KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); td = FIRST_THREAD_IN_PROC(p); /* Lock the last thread so we spin until it exits cpu_throw(). */ thread_lock(td); thread_unlock(td); lock_profile_thread_exit(td); cpuset_rel(td->td_cpuset); td->td_cpuset = NULL; cpu_thread_clean(td); thread_cow_free(td); callout_drain(&td->td_slpcallout); thread_reap(); /* check for zombie threads etc. */ } /* * Link a thread to a process. * set up anything that needs to be initialized for it to * be used by the process. */ void thread_link(struct thread *td, struct proc *p) { /* * XXX This can't be enabled because it's called for proc0 before * its lock has been created. * PROC_LOCK_ASSERT(p, MA_OWNED); */ TD_SET_STATE(td, TDS_INACTIVE); td->td_proc = p; td->td_flags = TDF_INMEM; LIST_INIT(&td->td_contested); LIST_INIT(&td->td_lprof[0]); LIST_INIT(&td->td_lprof[1]); #ifdef EPOCH_TRACE SLIST_INIT(&td->td_epochs); #endif sigqueue_init(&td->td_sigqueue, p); callout_init(&td->td_slpcallout, 1); TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); p->p_numthreads++; } /* * Called from: * thread_exit() */ void thread_unlink(struct thread *td) { struct proc *p = td->td_proc; PROC_LOCK_ASSERT(p, MA_OWNED); #ifdef EPOCH_TRACE MPASS(SLIST_EMPTY(&td->td_epochs)); #endif TAILQ_REMOVE(&p->p_threads, td, td_plist); p->p_numthreads--; /* could clear a few other things here */ /* Must NOT clear links to proc! */ } static int calc_remaining(struct proc *p, int mode) { int remaining; PROC_LOCK_ASSERT(p, MA_OWNED); PROC_SLOCK_ASSERT(p, MA_OWNED); if (mode == SINGLE_EXIT) remaining = p->p_numthreads; else if (mode == SINGLE_BOUNDARY) remaining = p->p_numthreads - p->p_boundary_count; else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) remaining = p->p_numthreads - p->p_suspcount; else panic("calc_remaining: wrong mode %d", mode); return (remaining); } static int remain_for_mode(int mode) { return (mode == SINGLE_ALLPROC ? 0 : 1); } static int weed_inhib(int mode, struct thread *td2, struct proc *p) { int wakeup_swapper; PROC_LOCK_ASSERT(p, MA_OWNED); PROC_SLOCK_ASSERT(p, MA_OWNED); THREAD_LOCK_ASSERT(td2, MA_OWNED); wakeup_swapper = 0; /* * Since the thread lock is dropped by the scheduler we have * to retry to check for races. */ restart: switch (mode) { case SINGLE_EXIT: if (TD_IS_SUSPENDED(td2)) { wakeup_swapper |= thread_unsuspend_one(td2, p, true); thread_lock(td2); goto restart; } if (TD_CAN_ABORT(td2)) { wakeup_swapper |= sleepq_abort(td2, EINTR); return (wakeup_swapper); } break; case SINGLE_BOUNDARY: case SINGLE_NO_EXIT: if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0) { wakeup_swapper |= thread_unsuspend_one(td2, p, false); thread_lock(td2); goto restart; } if (TD_CAN_ABORT(td2)) { wakeup_swapper |= sleepq_abort(td2, ERESTART); return (wakeup_swapper); } break; case SINGLE_ALLPROC: /* * ALLPROC suspend tries to avoid spurious EINTR for * threads sleeping interruptable, by suspending the * thread directly, similarly to sig_suspend_threads(). * Since such sleep is not neccessary performed at the user * boundary, TDF_ALLPROCSUSP is used to avoid immediate * un-suspend. */ if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_ALLPROCSUSP) == 0) { wakeup_swapper |= thread_unsuspend_one(td2, p, false); thread_lock(td2); goto restart; } if (TD_CAN_ABORT(td2)) { td2->td_flags |= TDF_ALLPROCSUSP; wakeup_swapper |= sleepq_abort(td2, ERESTART); return (wakeup_swapper); } break; default: break; } thread_unlock(td2); return (wakeup_swapper); } /* * Enforce single-threading. * * Returns 1 if the caller must abort (another thread is waiting to * exit the process or similar). Process is locked! * Returns 0 when you are successfully the only thread running. * A process has successfully single threaded in the suspend mode when * There are no threads in user mode. Threads in the kernel must be * allowed to continue until they get to the user boundary. They may even * copy out their return values and data before suspending. They may however be * accelerated in reaching the user boundary as we will wake up * any sleeping threads that are interruptable. (PCATCH). */ int thread_single(struct proc *p, int mode) { struct thread *td; struct thread *td2; int remaining, wakeup_swapper; td = curthread; KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, ("invalid mode %d", mode)); /* * If allowing non-ALLPROC singlethreading for non-curproc * callers, calc_remaining() and remain_for_mode() should be * adjusted to also account for td->td_proc != p. For now * this is not implemented because it is not used. */ KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || (mode != SINGLE_ALLPROC && td->td_proc == p), ("mode %d proc %p curproc %p", mode, p, td->td_proc)); mtx_assert(&Giant, MA_NOTOWNED); PROC_LOCK_ASSERT(p, MA_OWNED); /* * Is someone already single threading? * Or may be singlethreading is not needed at all. */ if (mode == SINGLE_ALLPROC) { while ((p->p_flag & P_STOPPED_SINGLE) != 0) { if ((p->p_flag2 & P2_WEXIT) != 0) return (1); msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0); } } else if ((p->p_flag & P_HADTHREADS) == 0) return (0); if (p->p_singlethread != NULL && p->p_singlethread != td) return (1); if (mode == SINGLE_EXIT) { p->p_flag |= P_SINGLE_EXIT; p->p_flag &= ~P_SINGLE_BOUNDARY; } else { p->p_flag &= ~P_SINGLE_EXIT; if (mode == SINGLE_BOUNDARY) p->p_flag |= P_SINGLE_BOUNDARY; else p->p_flag &= ~P_SINGLE_BOUNDARY; } if (mode == SINGLE_ALLPROC) { p->p_flag |= P_TOTAL_STOP; thread_lock(td); td->td_flags |= TDF_DOING_SA; thread_unlock(td); } p->p_flag |= P_STOPPED_SINGLE; PROC_SLOCK(p); p->p_singlethread = td; remaining = calc_remaining(p, mode); while (remaining != remain_for_mode(mode)) { if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) goto stopme; wakeup_swapper = 0; FOREACH_THREAD_IN_PROC(p, td2) { if (td2 == td) continue; thread_lock(td2); ast_sched_locked(td2, TDA_SUSPEND); if (TD_IS_INHIBITED(td2)) { wakeup_swapper |= weed_inhib(mode, td2, p); #ifdef SMP } else if (TD_IS_RUNNING(td2)) { forward_signal(td2); thread_unlock(td2); #endif } else thread_unlock(td2); } if (wakeup_swapper) kick_proc0(); remaining = calc_remaining(p, mode); /* * Maybe we suspended some threads.. was it enough? */ if (remaining == remain_for_mode(mode)) break; stopme: /* * Wake us up when everyone else has suspended. * In the mean time we suspend as well. */ thread_suspend_switch(td, p); remaining = calc_remaining(p, mode); } if (mode == SINGLE_EXIT) { /* * Convert the process to an unthreaded process. The * SINGLE_EXIT is called by exit1() or execve(), in * both cases other threads must be retired. */ KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); p->p_singlethread = NULL; p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); /* * Wait for any remaining threads to exit cpu_throw(). */ while (p->p_exitthreads != 0) { PROC_SUNLOCK(p); PROC_UNLOCK(p); sched_relinquish(td); PROC_LOCK(p); PROC_SLOCK(p); } } else if (mode == SINGLE_BOUNDARY) { /* * Wait until all suspended threads are removed from * the processors. The thread_suspend_check() * increments p_boundary_count while it is still * running, which makes it possible for the execve() * to destroy vmspace while our other threads are * still using the address space. * * We lock the thread, which is only allowed to * succeed after context switch code finished using * the address space. */ FOREACH_THREAD_IN_PROC(p, td2) { if (td2 == td) continue; thread_lock(td2); KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, ("td %p not on boundary", td2)); KASSERT(TD_IS_SUSPENDED(td2), ("td %p is not suspended", td2)); thread_unlock(td2); } } PROC_SUNLOCK(p); if (mode == SINGLE_ALLPROC) { thread_lock(td); td->td_flags &= ~TDF_DOING_SA; thread_unlock(td); } return (0); } bool thread_suspend_check_needed(void) { struct proc *p; struct thread *td; td = curthread; p = td->td_proc; PROC_LOCK_ASSERT(p, MA_OWNED); return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && (td->td_dbgflags & TDB_SUSPEND) != 0)); } /* * Called in from locations that can safely check to see * whether we have to suspend or at least throttle for a * single-thread event (e.g. fork). * * Such locations include userret(). * If the "return_instead" argument is non zero, the thread must be able to * accept 0 (caller may continue), or 1 (caller must abort) as a result. * * The 'return_instead' argument tells the function if it may do a * thread_exit() or suspend, or whether the caller must abort and back * out instead. * * If the thread that set the single_threading request has set the * P_SINGLE_EXIT bit in the process flags then this call will never return * if 'return_instead' is false, but will exit. * * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 *---------------+--------------------+--------------------- * 0 | returns 0 | returns 0 or 1 * | when ST ends | immediately *---------------+--------------------+--------------------- * 1 | thread exits | returns 1 * | | immediately * 0 = thread_exit() or suspension ok, * other = return error instead of stopping the thread. * * While a full suspension is under effect, even a single threading * thread would be suspended if it made this call (but it shouldn't). * This call should only be made from places where * thread_exit() would be safe as that may be the outcome unless * return_instead is set. */ int thread_suspend_check(int return_instead) { struct thread *td; struct proc *p; int wakeup_swapper; td = curthread; p = td->td_proc; mtx_assert(&Giant, MA_NOTOWNED); PROC_LOCK_ASSERT(p, MA_OWNED); while (thread_suspend_check_needed()) { if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { KASSERT(p->p_singlethread != NULL, ("singlethread not set")); /* * The only suspension in action is a * single-threading. Single threader need not stop. * It is safe to access p->p_singlethread unlocked * because it can only be set to our address by us. */ if (p->p_singlethread == td) return (0); /* Exempt from stopping. */ } if ((p->p_flag & P_SINGLE_EXIT) && return_instead) return (EINTR); /* Should we goto user boundary if we didn't come from there? */ if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) return (ERESTART); /* * Ignore suspend requests if they are deferred. */ if ((td->td_flags & TDF_SBDRY) != 0) { KASSERT(return_instead, ("TDF_SBDRY set for unsafe thread_suspend_check")); KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != (TDF_SEINTR | TDF_SERESTART), ("both TDF_SEINTR and TDF_SERESTART")); return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); } /* * If the process is waiting for us to exit, * this thread should just suicide. * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. */ if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { PROC_UNLOCK(p); /* * Allow Linux emulation layer to do some work * before thread suicide. */ if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) (p->p_sysent->sv_thread_detach)(td); umtx_thread_exit(td); kern_thr_exit(td); panic("stopped thread did not exit"); } PROC_SLOCK(p); thread_stopped(p); if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { if (p->p_numthreads == p->p_suspcount + 1) { thread_lock(p->p_singlethread); wakeup_swapper = thread_unsuspend_one( p->p_singlethread, p, false); if (wakeup_swapper) kick_proc0(); } } PROC_UNLOCK(p); thread_lock(td); /* * When a thread suspends, it just * gets taken off all queues. */ thread_suspend_one(td); if (return_instead == 0) { p->p_boundary_count++; td->td_flags |= TDF_BOUNDARY; } PROC_SUNLOCK(p); mi_switch(SW_INVOL | SWT_SUSPEND); PROC_LOCK(p); } return (0); } /* * Check for possible stops and suspensions while executing a * casueword or similar transiently failing operation. * * The sleep argument controls whether the function can handle a stop * request itself or it should return ERESTART and the request is * proceed at the kernel/user boundary in ast. * * Typically, when retrying due to casueword(9) failure (rv == 1), we * should handle the stop requests there, with exception of cases when * the thread owns a kernel resource, for instance busied the umtx * key, or when functions return immediately if thread_check_susp() * returned non-zero. On the other hand, retrying the whole lock * operation, we better not stop there but delegate the handling to * ast. * * If the request is for thread termination P_SINGLE_EXIT, we cannot * handle it at all, and simply return EINTR. */ int thread_check_susp(struct thread *td, bool sleep) { struct proc *p; int error; /* * The check for TDA_SUSPEND is racy, but it is enough to * eventually break the lockstep loop. */ if (!td_ast_pending(td, TDA_SUSPEND)) return (0); error = 0; p = td->td_proc; PROC_LOCK(p); if (p->p_flag & P_SINGLE_EXIT) error = EINTR; else if (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) error = sleep ? thread_suspend_check(0) : ERESTART; PROC_UNLOCK(p); return (error); } void thread_suspend_switch(struct thread *td, struct proc *p) { KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); PROC_LOCK_ASSERT(p, MA_OWNED); PROC_SLOCK_ASSERT(p, MA_OWNED); /* * We implement thread_suspend_one in stages here to avoid * dropping the proc lock while the thread lock is owned. */ if (p == td->td_proc) { thread_stopped(p); p->p_suspcount++; } PROC_UNLOCK(p); thread_lock(td); ast_unsched_locked(td, TDA_SUSPEND); TD_SET_SUSPENDED(td); sched_sleep(td, 0); PROC_SUNLOCK(p); DROP_GIANT(); mi_switch(SW_VOL | SWT_SUSPEND); PICKUP_GIANT(); PROC_LOCK(p); PROC_SLOCK(p); } void thread_suspend_one(struct thread *td) { struct proc *p; p = td->td_proc; PROC_SLOCK_ASSERT(p, MA_OWNED); THREAD_LOCK_ASSERT(td, MA_OWNED); KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); p->p_suspcount++; ast_unsched_locked(td, TDA_SUSPEND); TD_SET_SUSPENDED(td); sched_sleep(td, 0); } static int thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) { THREAD_LOCK_ASSERT(td, MA_OWNED); KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); TD_CLR_SUSPENDED(td); td->td_flags &= ~TDF_ALLPROCSUSP; if (td->td_proc == p) { PROC_SLOCK_ASSERT(p, MA_OWNED); p->p_suspcount--; if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { td->td_flags &= ~TDF_BOUNDARY; p->p_boundary_count--; } } return (setrunnable(td, 0)); } void thread_run_flash(struct thread *td) { struct proc *p; p = td->td_proc; PROC_LOCK_ASSERT(p, MA_OWNED); if (TD_ON_SLEEPQ(td)) sleepq_remove_nested(td); else thread_lock(td); THREAD_LOCK_ASSERT(td, MA_OWNED); KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); TD_CLR_SUSPENDED(td); PROC_SLOCK(p); MPASS(p->p_suspcount > 0); p->p_suspcount--; PROC_SUNLOCK(p); if (setrunnable(td, 0)) kick_proc0(); } /* * Allow all threads blocked by single threading to continue running. */ void thread_unsuspend(struct proc *p) { struct thread *td; int wakeup_swapper; PROC_LOCK_ASSERT(p, MA_OWNED); PROC_SLOCK_ASSERT(p, MA_OWNED); wakeup_swapper = 0; if (!P_SHOULDSTOP(p)) { FOREACH_THREAD_IN_PROC(p, td) { thread_lock(td); if (TD_IS_SUSPENDED(td) && (td->td_flags & TDF_DOING_SA) == 0) { wakeup_swapper |= thread_unsuspend_one(td, p, true); } else thread_unlock(td); } } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && p->p_numthreads == p->p_suspcount) { /* * Stopping everything also did the job for the single * threading request. Now we've downgraded to single-threaded, * let it continue. */ if (p->p_singlethread->td_proc == p) { thread_lock(p->p_singlethread); wakeup_swapper = thread_unsuspend_one( p->p_singlethread, p, false); } } if (wakeup_swapper) kick_proc0(); } /* * End the single threading mode.. */ void thread_single_end(struct proc *p, int mode) { struct thread *td; int wakeup_swapper; KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, ("invalid mode %d", mode)); PROC_LOCK_ASSERT(p, MA_OWNED); KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), ("mode %d does not match P_TOTAL_STOP", mode)); KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, ("thread_single_end from other thread %p %p", curthread, p->p_singlethread)); KASSERT(mode != SINGLE_BOUNDARY || (p->p_flag & P_SINGLE_BOUNDARY) != 0, ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | P_TOTAL_STOP); PROC_SLOCK(p); p->p_singlethread = NULL; wakeup_swapper = 0; /* * If there are other threads they may now run, * unless of course there is a blanket 'stop order' * on the process. The single threader must be allowed * to continue however as this is a bad place to stop. */ if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { FOREACH_THREAD_IN_PROC(p, td) { thread_lock(td); if (TD_IS_SUSPENDED(td)) { wakeup_swapper |= thread_unsuspend_one(td, p, true); } else thread_unlock(td); } } KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, ("inconsistent boundary count %d", p->p_boundary_count)); PROC_SUNLOCK(p); if (wakeup_swapper) kick_proc0(); wakeup(&p->p_flag); } /* * Locate a thread by number and return with proc lock held. * * thread exit establishes proc -> tidhash lock ordering, but lookup * takes tidhash first and needs to return locked proc. * * The problem is worked around by relying on type-safety of both * structures and doing the work in 2 steps: * - tidhash-locked lookup which saves both thread and proc pointers * - proc-locked verification that the found thread still matches */ static bool tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) { #define RUN_THRESH 16 struct proc *p; struct thread *td; int run; bool locked; run = 0; rw_rlock(TIDHASHLOCK(tid)); locked = true; LIST_FOREACH(td, TIDHASH(tid), td_hash) { if (td->td_tid != tid) { run++; continue; } p = td->td_proc; if (pid != -1 && p->p_pid != pid) { td = NULL; break; } if (run > RUN_THRESH) { if (rw_try_upgrade(TIDHASHLOCK(tid))) { LIST_REMOVE(td, td_hash); LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); rw_wunlock(TIDHASHLOCK(tid)); locked = false; break; } } break; } if (locked) rw_runlock(TIDHASHLOCK(tid)); if (td == NULL) return (false); *pp = p; *tdp = td; return (true); } struct thread * tdfind(lwpid_t tid, pid_t pid) { struct proc *p; struct thread *td; td = curthread; if (td->td_tid == tid) { if (pid != -1 && td->td_proc->p_pid != pid) return (NULL); PROC_LOCK(td->td_proc); return (td); } for (;;) { if (!tdfind_hash(tid, pid, &p, &td)) return (NULL); PROC_LOCK(p); if (td->td_tid != tid) { PROC_UNLOCK(p); continue; } if (td->td_proc != p) { PROC_UNLOCK(p); continue; } if (p->p_state == PRS_NEW) { PROC_UNLOCK(p); return (NULL); } return (td); } } void tidhash_add(struct thread *td) { rw_wlock(TIDHASHLOCK(td->td_tid)); LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); rw_wunlock(TIDHASHLOCK(td->td_tid)); } void tidhash_remove(struct thread *td) { rw_wlock(TIDHASHLOCK(td->td_tid)); LIST_REMOVE(td, td_hash); rw_wunlock(TIDHASHLOCK(td->td_tid)); }