/* * linux/kernel/exit.c * * Copyright (C) 1991, 1992 Linus Torvalds */ #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 #include #include #include #include #include #include #include #include #include #include #include /* for audit_free() */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include static void exit_mm(struct task_struct * tsk); static void __unhash_process(struct task_struct *p, bool group_dead) { nr_threads--; detach_pid(p, PIDTYPE_PID); if (group_dead) { detach_pid(p, PIDTYPE_PGID); detach_pid(p, PIDTYPE_SID); list_del_rcu(&p->tasks); list_del_init(&p->sibling); __this_cpu_dec(process_counts); } list_del_rcu(&p->thread_group); } /* * This function expects the tasklist_lock write-locked. */ static void __exit_signal(struct task_struct *tsk) { struct signal_struct *sig = tsk->signal; bool group_dead = thread_group_leader(tsk); struct sighand_struct *sighand; struct tty_struct *uninitialized_var(tty); sighand = rcu_dereference_check(tsk->sighand, lockdep_tasklist_lock_is_held()); spin_lock(&sighand->siglock); posix_cpu_timers_exit(tsk); if (group_dead) { posix_cpu_timers_exit_group(tsk); tty = sig->tty; sig->tty = NULL; } else { /* * This can only happen if the caller is de_thread(). * FIXME: this is the temporary hack, we should teach * posix-cpu-timers to handle this case correctly. */ if (unlikely(has_group_leader_pid(tsk))) posix_cpu_timers_exit_group(tsk); /* * If there is any task waiting for the group exit * then notify it: */ if (sig->notify_count > 0 && !--sig->notify_count) wake_up_process(sig->group_exit_task); if (tsk == sig->curr_target) sig->curr_target = next_thread(tsk); /* * Accumulate here the counters for all threads but the * group leader as they die, so they can be added into * the process-wide totals when those are taken. * The group leader stays around as a zombie as long * as there are other threads. When it gets reaped, * the exit.c code will add its counts into these totals. * We won't ever get here for the group leader, since it * will have been the last reference on the signal_struct. */ sig->utime = cputime_add(sig->utime, tsk->utime); sig->stime = cputime_add(sig->stime, tsk->stime); sig->gtime = cputime_add(sig->gtime, tsk->gtime); sig->min_flt += tsk->min_flt; sig->maj_flt += tsk->maj_flt; sig->nvcsw += tsk->nvcsw; sig->nivcsw += tsk->nivcsw; sig->inblock += task_io_get_inblock(tsk); sig->oublock += task_io_get_oublock(tsk); task_io_accounting_add(&sig->ioac, &tsk->ioac); sig->sum_sched_runtime += tsk->se.sum_exec_runtime; } sig->nr_threads--; __unhash_process(tsk, group_dead); /* * Do this under ->siglock, we can race with another thread * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals. */ flush_sigqueue(&tsk->pending); tsk->sighand = NULL; spin_unlock(&sighand->siglock); __cleanup_sighand(sighand); clear_tsk_thread_flag(tsk,TIF_SIGPENDING); if (group_dead) { flush_sigqueue(&sig->shared_pending); tty_kref_put(tty); } } static void delayed_put_task_struct(struct rcu_head *rhp) { struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); perf_event_delayed_put(tsk); trace_sched_process_free(tsk); put_task_struct(tsk); } void release_task(struct task_struct * p) { struct task_struct *leader; int zap_leader; repeat: /* don't need to get the RCU readlock here - the process is dead and * can't be modifying its own credentials. But shut RCU-lockdep up */ rcu_read_lock(); atomic_dec(&__task_cred(p)->user->processes); rcu_read_unlock(); proc_flush_task(p); write_lock_irq(&tasklist_lock); ptrace_release_task(p); __exit_signal(p); /* * If we are the last non-leader member of the thread * group, and the leader is zombie, then notify the * group leader's parent process. (if it wants notification.) */ zap_leader = 0; leader = p->group_leader; if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) { /* * If we were the last child thread and the leader has * exited already, and the leader's parent ignores SIGCHLD, * then we are the one who should release the leader. */ zap_leader = do_notify_parent(leader, leader->exit_signal); if (zap_leader) leader->exit_state = EXIT_DEAD; } write_unlock_irq(&tasklist_lock); release_thread(p); call_rcu(&p->rcu, delayed_put_task_struct); p = leader; if (unlikely(zap_leader)) goto repeat; } /* * This checks not only the pgrp, but falls back on the pid if no * satisfactory pgrp is found. I dunno - gdb doesn't work correctly * without this... * * The caller must hold rcu lock or the tasklist lock. */ struct pid *session_of_pgrp(struct pid *pgrp) { struct task_struct *p; struct pid *sid = NULL; p = pid_task(pgrp, PIDTYPE_PGID); if (p == NULL) p = pid_task(pgrp, PIDTYPE_PID); if (p != NULL) sid = task_session(p); return sid; } /* * Determine if a process group is "orphaned", according to the POSIX * definition in 2.2.2.52. Orphaned process groups are not to be affected * by terminal-generated stop signals. Newly orphaned process groups are * to receive a SIGHUP and a SIGCONT. * * "I ask you, have you ever known what it is to be an orphan?" */ static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task) { struct task_struct *p; do_each_pid_task(pgrp, PIDTYPE_PGID, p) { if ((p == ignored_task) || (p->exit_state && thread_group_empty(p)) || is_global_init(p->real_parent)) continue; if (task_pgrp(p->real_parent) != pgrp && task_session(p->real_parent) == task_session(p)) return 0; } while_each_pid_task(pgrp, PIDTYPE_PGID, p); return 1; } int is_current_pgrp_orphaned(void) { int retval; read_lock(&tasklist_lock); retval = will_become_orphaned_pgrp(task_pgrp(current), NULL); read_unlock(&tasklist_lock); return retval; } static bool has_stopped_jobs(struct pid *pgrp) { struct task_struct *p; do_each_pid_task(pgrp, PIDTYPE_PGID, p) { if (p->signal->flags & SIGNAL_STOP_STOPPED) return true; } while_each_pid_task(pgrp, PIDTYPE_PGID, p); return false; } /* * Check to see if any process groups have become orphaned as * a result of our exiting, and if they have any stopped jobs, * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) */ static void kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent) { struct pid *pgrp = task_pgrp(tsk); struct task_struct *ignored_task = tsk; if (!parent) /* exit: our father is in a different pgrp than * we are and we were the only connection outside. */ parent = tsk->real_parent; else /* reparent: our child is in a different pgrp than * we are, and it was the only connection outside. */ ignored_task = NULL; if (task_pgrp(parent) != pgrp && task_session(parent) == task_session(tsk) && will_become_orphaned_pgrp(pgrp, ignored_task) && has_stopped_jobs(pgrp)) { __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp); __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp); } } /** * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd * * If a kernel thread is launched as a result of a system call, or if * it ever exits, it should generally reparent itself to kthreadd so it * isn't in the way of other processes and is correctly cleaned up on exit. * * The various task state such as scheduling policy and priority may have * been inherited from a user process, so we reset them to sane values here. * * NOTE that reparent_to_kthreadd() gives the caller full capabilities. */ static void reparent_to_kthreadd(void) { write_lock_irq(&tasklist_lock); ptrace_unlink(current); /* Reparent to init */ current->real_parent = current->parent = kthreadd_task; list_move_tail(¤t->sibling, ¤t->real_parent->children); /* Set the exit signal to SIGCHLD so we signal init on exit */ current->exit_signal = SIGCHLD; if (task_nice(current) < 0) set_user_nice(current, 0); /* cpus_allowed? */ /* rt_priority? */ /* signals? */ memcpy(current->signal->rlim, init_task.signal->rlim, sizeof(current->signal->rlim)); atomic_inc(&init_cred.usage); commit_creds(&init_cred); write_unlock_irq(&tasklist_lock); } void __set_special_pids(struct pid *pid) { struct task_struct *curr = current->group_leader; if (task_session(curr) != pid) change_pid(curr, PIDTYPE_SID, pid); if (task_pgrp(curr) != pid) change_pid(curr, PIDTYPE_PGID, pid); } static void set_special_pids(struct pid *pid) { write_lock_irq(&tasklist_lock); __set_special_pids(pid); write_unlock_irq(&tasklist_lock); } /* * Let kernel threads use this to say that they allow a certain signal. * Must not be used if kthread was cloned with CLONE_SIGHAND. */ int allow_signal(int sig) { if (!valid_signal(sig) || sig < 1) return -EINVAL; spin_lock_irq(¤t->sighand->siglock); /* This is only needed for daemonize()'ed kthreads */ sigdelset(¤t->blocked, sig); /* * Kernel threads handle their own signals. Let the signal code * know it'll be handled, so that they don't get converted to * SIGKILL or just silently dropped. */ current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2; recalc_sigpending(); spin_unlock_irq(¤t->sighand->siglock); return 0; } EXPORT_SYMBOL(allow_signal); int disallow_signal(int sig) { if (!valid_signal(sig) || sig < 1) return -EINVAL; spin_lock_irq(¤t->sighand->siglock); current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN; recalc_sigpending(); spin_unlock_irq(¤t->sighand->siglock); return 0; } EXPORT_SYMBOL(disallow_signal); /* * Put all the gunge required to become a kernel thread without * attached user resources in one place where it belongs. */ void daemonize(const char *name, ...) { va_list args; sigset_t blocked; va_start(args, name); vsnprintf(current->comm, sizeof(current->comm), name, args); va_end(args); /* * If we were started as result of loading a module, close all of the * user space pages. We don't need them, and if we didn't close them * they would be locked into memory. */ exit_mm(current); /* * We don't want to have TIF_FREEZE set if the system-wide hibernation * or suspend transition begins right now. */ current->flags |= (PF_NOFREEZE | PF_KTHREAD); if (current->nsproxy != &init_nsproxy) { get_nsproxy(&init_nsproxy); switch_task_namespaces(current, &init_nsproxy); } set_special_pids(&init_struct_pid); proc_clear_tty(current); /* Block and flush all signals */ sigfillset(&blocked); sigprocmask(SIG_BLOCK, &blocked, NULL); flush_signals(current); /* Become as one with the init task */ daemonize_fs_struct(); exit_files(current); current->files = init_task.files; atomic_inc(¤t->files->count); reparent_to_kthreadd(); } EXPORT_SYMBOL(daemonize); static void close_files(struct files_struct * files) { int i, j; struct fdtable *fdt; j = 0; /* * It is safe to dereference the fd table without RCU or * ->file_lock because this is the last reference to the * files structure. But use RCU to shut RCU-lockdep up. */ rcu_read_lock(); fdt = files_fdtable(files); rcu_read_unlock(); for (;;) { unsigned long set; i = j * __NFDBITS; if (i >= fdt->max_fds) break; set = fdt->open_fds->fds_bits[j++]; while (set) { if (set & 1) { struct file * file = xchg(&fdt->fd[i], NULL); if (file) { filp_close(file, files); cond_resched(); } } i++; set >>= 1; } } } struct files_struct *get_files_struct(struct task_struct *task) { struct files_struct *files; task_lock(task); files = task->files; if (files) atomic_inc(&files->count); task_unlock(task); return files; } void put_files_struct(struct files_struct *files) { struct fdtable *fdt; if (atomic_dec_and_test(&files->count)) { close_files(files); /* * Free the fd and fdset arrays if we expanded them. * If the fdtable was embedded, pass files for freeing * at the end of the RCU grace period. Otherwise, * you can free files immediately. */ rcu_read_lock(); fdt = files_fdtable(files); if (fdt != &files->fdtab) kmem_cache_free(files_cachep, files); free_fdtable(fdt); rcu_read_unlock(); } } void reset_files_struct(struct files_struct *files) { struct task_struct *tsk = current; struct files_struct *old; old = tsk->files; task_lock(tsk); tsk->files = files; task_unlock(tsk); put_files_struct(old); } void exit_files(struct task_struct *tsk) { struct files_struct * files = tsk->files; if (files) { task_lock(tsk); tsk->files = NULL; task_unlock(tsk); put_files_struct(files); } } #ifdef CONFIG_MM_OWNER /* * A task is exiting. If it owned this mm, find a new owner for the mm. */ void mm_update_next_owner(struct mm_struct *mm) { struct task_struct *c, *g, *p = current; retry: /* * If the exiting or execing task is not the owner, it's * someone else's problem. */ if (mm->owner != p) return; /* * The current owner is exiting/execing and there are no other * candidates. Do not leave the mm pointing to a possibly * freed task structure. */ if (atomic_read(&mm->mm_users) <= 1) { mm->owner = NULL; return; } read_lock(&tasklist_lock); /* * Search in the children */ list_for_each_entry(c, &p->children, sibling) { if (c->mm == mm) goto assign_new_owner; } /* * Search in the siblings */ list_for_each_entry(c, &p->real_parent->children, sibling) { if (c->mm == mm) goto assign_new_owner; } /* * Search through everything else. We should not get * here often */ do_each_thread(g, c) { if (c->mm == mm) goto assign_new_owner; } while_each_thread(g, c); read_unlock(&tasklist_lock); /* * We found no owner yet mm_users > 1: this implies that we are * most likely racing with swapoff (try_to_unuse()) or /proc or * ptrace or page migration (get_task_mm()). Mark owner as NULL. */ mm->owner = NULL; return; assign_new_owner: BUG_ON(c == p); get_task_struct(c); /* * The task_lock protects c->mm from changing. * We always want mm->owner->mm == mm */ task_lock(c); /* * Delay read_unlock() till we have the task_lock() * to ensure that c does not slip away underneath us */ read_unlock(&tasklist_lock); if (c->mm != mm) { task_unlock(c); put_task_struct(c); goto retry; } mm->owner = c; task_unlock(c); put_task_struct(c); } #endif /* CONFIG_MM_OWNER */ /* * Turn us into a lazy TLB process if we * aren't already.. */ static void exit_mm(struct task_struct * tsk) { struct mm_struct *mm = tsk->mm; struct core_state *core_state; mm_release(tsk, mm); if (!mm) return; /* * Serialize with any possible pending coredump. * We must hold mmap_sem around checking core_state * and clearing tsk->mm. The core-inducing thread * will increment ->nr_threads for each thread in the * group with ->mm != NULL. */ down_read(&mm->mmap_sem); core_state = mm->core_state; if (core_state) { struct core_thread self; up_read(&mm->mmap_sem); self.task = tsk; self.next = xchg(&core_state->dumper.next, &self); /* * Implies mb(), the result of xchg() must be visible * to core_state->dumper. */ if (atomic_dec_and_test(&core_state->nr_threads)) complete(&core_state->startup); for (;;) { set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (!self.task) /* see coredump_finish() */ break; schedule(); } __set_task_state(tsk, TASK_RUNNING); down_read(&mm->mmap_sem); } atomic_inc(&mm->mm_count); BUG_ON(mm != tsk->active_mm); /* more a memory barrier than a real lock */ task_lock(tsk); tsk->mm = NULL; up_read(&mm->mmap_sem); enter_lazy_tlb(mm, current); /* We don't want this task to be frozen prematurely */ clear_freeze_flag(tsk); task_unlock(tsk); mm_update_next_owner(mm); mmput(mm); } /* * When we die, we re-parent all our children. * Try to give them to another thread in our thread * group, and if no such member exists, give it to * the child reaper process (ie "init") in our pid * space. */ static struct task_struct *find_new_reaper(struct task_struct *father) __releases(&tasklist_lock) __acquires(&tasklist_lock) { struct pid_namespace *pid_ns = task_active_pid_ns(father); struct task_struct *thread; thread = father; while_each_thread(father, thread) { if (thread->flags & PF_EXITING) continue; if (unlikely(pid_ns->child_reaper == father)) pid_ns->child_reaper = thread; return thread; } if (unlikely(pid_ns->child_reaper == father)) { write_unlock_irq(&tasklist_lock); if (unlikely(pid_ns == &init_pid_ns)) panic("Attempted to kill init!"); zap_pid_ns_processes(pid_ns); write_lock_irq(&tasklist_lock); /* * We can not clear ->child_reaper or leave it alone. * There may by stealth EXIT_DEAD tasks on ->children, * forget_original_parent() must move them somewhere. */ pid_ns->child_reaper = init_pid_ns.child_reaper; } return pid_ns->child_reaper; } /* * Any that need to be release_task'd are put on the @dead list. */ static void reparent_leader(struct task_struct *father, struct task_struct *p, struct list_head *dead) { list_move_tail(&p->sibling, &p->real_parent->children); if (p->exit_state == EXIT_DEAD) return; /* * If this is a threaded reparent there is no need to * notify anyone anything has happened. */ if (same_thread_group(p->real_parent, father)) return; /* We don't want people slaying init. */ p->exit_signal = SIGCHLD; /* If it has exited notify the new parent about this child's death. */ if (!p->ptrace && p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) { if (do_notify_parent(p, p->exit_signal)) { p->exit_state = EXIT_DEAD; list_move_tail(&p->sibling, dead); } } kill_orphaned_pgrp(p, father); } static void forget_original_parent(struct task_struct *father) { struct task_struct *p, *n, *reaper; LIST_HEAD(dead_children); write_lock_irq(&tasklist_lock); /* * Note that exit_ptrace() and find_new_reaper() might * drop tasklist_lock and reacquire it. */ exit_ptrace(father); reaper = find_new_reaper(father); list_for_each_entry_safe(p, n, &father->children, sibling) { struct task_struct *t = p; do { t->real_parent = reaper; if (t->parent == father) { BUG_ON(t->ptrace); t->parent = t->real_parent; } if (t->pdeath_signal) group_send_sig_info(t->pdeath_signal, SEND_SIG_NOINFO, t); } while_each_thread(p, t); reparent_leader(father, p, &dead_children); } write_unlock_irq(&tasklist_lock); BUG_ON(!list_empty(&father->children)); list_for_each_entry_safe(p, n, &dead_children, sibling) { list_del_init(&p->sibling); release_task(p); } } /* * Send signals to all our closest relatives so that they know * to properly mourn us.. */ static void exit_notify(struct task_struct *tsk, int group_dead) { bool autoreap; /* * This does two things: * * A. Make init inherit all the child processes * B. Check to see if any process groups have become orphaned * as a result of our exiting, and if they have any stopped * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) */ forget_original_parent(tsk); exit_task_namespaces(tsk); write_lock_irq(&tasklist_lock); if (group_dead) kill_orphaned_pgrp(tsk->group_leader, NULL); if (unlikely(tsk->ptrace)) { int sig = thread_group_leader(tsk) && thread_group_empty(tsk) && !ptrace_reparented(tsk) ? tsk->exit_signal : SIGCHLD; autoreap = do_notify_parent(tsk, sig); } else if (thread_group_leader(tsk)) { autoreap = thread_group_empty(tsk) && do_notify_parent(tsk, tsk->exit_signal); } else { autoreap = true; } tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE; /* mt-exec, de_thread() is waiting for group leader */ if (unlikely(tsk->signal->notify_count < 0)) wake_up_process(tsk->signal->group_exit_task); write_unlock_irq(&tasklist_lock); /* If the process is dead, release it - nobody will wait for it */ if (autoreap) release_task(tsk); } #ifdef CONFIG_DEBUG_STACK_USAGE static void check_stack_usage(void) { static DEFINE_SPINLOCK(low_water_lock); static int lowest_to_date = THREAD_SIZE; unsigned long free; free = stack_not_used(current); if (free >= lowest_to_date) return; spin_lock(&low_water_lock); if (free < lowest_to_date) { printk(KERN_WARNING "%s used greatest stack depth: %lu bytes " "left\n", current->comm, free); lowest_to_date = free; } spin_unlock(&low_water_lock); } #else static inline void check_stack_usage(void) {} #endif NORET_TYPE void do_exit(long code) { struct task_struct *tsk = current; int group_dead; profile_task_exit(tsk); WARN_ON(blk_needs_flush_plug(tsk)); if (unlikely(in_interrupt())) panic("Aiee, killing interrupt handler!"); if (unlikely(!tsk->pid)) panic("Attempted to kill the idle task!"); /* * If do_exit is called because this processes oopsed, it's possible * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before * continuing. Amongst other possible reasons, this is to prevent * mm_release()->clear_child_tid() from writing to a user-controlled * kernel address. */ set_fs(USER_DS); ptrace_event(PTRACE_EVENT_EXIT, code); validate_creds_for_do_exit(tsk); /* * We're taking recursive faults here in do_exit. Safest is to just * leave this task alone and wait for reboot. */ if (unlikely(tsk->flags & PF_EXITING)) { printk(KERN_ALERT "Fixing recursive fault but reboot is needed!\n"); /* * We can do this unlocked here. The futex code uses * this flag just to verify whether the pi state * cleanup has been done or not. In the worst case it * loops once more. We pretend that the cleanup was * done as there is no way to return. Either the * OWNER_DIED bit is set by now or we push the blocked * task into the wait for ever nirwana as well. */ tsk->flags |= PF_EXITPIDONE; set_current_state(TASK_UNINTERRUPTIBLE); schedule(); } exit_irq_thread(); exit_signals(tsk); /* sets PF_EXITING */ /* * tsk->flags are checked in the futex code to protect against * an exiting task cleaning up the robust pi futexes. */ smp_mb(); raw_spin_unlock_wait(&tsk->pi_lock); if (unlikely(in_atomic())) printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n", current->comm, task_pid_nr(current), preempt_count()); acct_update_integrals(tsk); /* sync mm's RSS info before statistics gathering */ if (tsk->mm) sync_mm_rss(tsk, tsk->mm); group_dead = atomic_dec_and_test(&tsk->signal->live); if (group_dead) { hrtimer_cancel(&tsk->signal->real_timer); exit_itimers(tsk->signal); if (tsk->mm) setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); } acct_collect(code, group_dead); if (group_dead) tty_audit_exit(); if (unlikely(tsk->audit_context)) audit_free(tsk); tsk->exit_code = code; taskstats_exit(tsk, group_dead); exit_mm(tsk); if (group_dead) acct_process(); trace_sched_process_exit(tsk); exit_sem(tsk); exit_shm(tsk); exit_files(tsk); exit_fs(tsk); check_stack_usage(); exit_thread(); /* * Flush inherited counters to the parent - before the parent * gets woken up by child-exit notifications. * * because of cgroup mode, must be called before cgroup_exit() */ perf_event_exit_task(tsk); cgroup_exit(tsk, 1); if (group_dead) disassociate_ctty(1); module_put(task_thread_info(tsk)->exec_domain->module); proc_exit_connector(tsk); /* * FIXME: do that only when needed, using sched_exit tracepoint */ ptrace_put_breakpoints(tsk); exit_notify(tsk, group_dead); #ifdef CONFIG_NUMA task_lock(tsk); mpol_put(tsk->mempolicy); tsk->mempolicy = NULL; task_unlock(tsk); #endif #ifdef CONFIG_FUTEX if (unlikely(current->pi_state_cache)) kfree(current->pi_state_cache); #endif /* * Make sure we are holding no locks: */ debug_check_no_locks_held(tsk); /* * We can do this unlocked here. The futex code uses this flag * just to verify whether the pi state cleanup has been done * or not. In the worst case it loops once more. */ tsk->flags |= PF_EXITPIDONE; if (tsk->io_context) exit_io_context(tsk); if (tsk->splice_pipe) __free_pipe_info(tsk->splice_pipe); validate_creds_for_do_exit(tsk); preempt_disable(); exit_rcu(); /* * The setting of TASK_RUNNING by try_to_wake_up() may be delayed * when the following two conditions become true. * - There is race condition of mmap_sem (It is acquired by * exit_mm()), and * - SMI occurs before setting TASK_RUNINNG. * (or hypervisor of virtual machine switches to other guest) * As a result, we may become TASK_RUNNING after becoming TASK_DEAD * * To avoid it, we have to wait for releasing tsk->pi_lock which * is held by try_to_wake_up() */ smp_mb(); raw_spin_unlock_wait(&tsk->pi_lock); /* causes final put_task_struct in finish_task_switch(). */ tsk->state = TASK_DEAD; schedule(); BUG(); /* Avoid "noreturn function does return". */ for (;;) cpu_relax(); /* For when BUG is null */ } EXPORT_SYMBOL_GPL(do_exit); NORET_TYPE void complete_and_exit(struct completion *comp, long code) { if (comp) complete(comp); do_exit(code); } EXPORT_SYMBOL(complete_and_exit); SYSCALL_DEFINE1(exit, int, error_code) { do_exit((error_code&0xff)<<8); } /* * Take down every thread in the group. This is called by fatal signals * as well as by sys_exit_group (below). */ NORET_TYPE void do_group_exit(int exit_code) { struct signal_struct *sig = current->signal; BUG_ON(exit_code & 0x80); /* core dumps don't get here */ if (signal_group_exit(sig)) exit_code = sig->group_exit_code; else if (!thread_group_empty(current)) { struct sighand_struct *const sighand = current->sighand; spin_lock_irq(&sighand->siglock); if (signal_group_exit(sig)) /* Another thread got here before we took the lock. */ exit_code = sig->group_exit_code; else { sig->group_exit_code = exit_code; sig->flags = SIGNAL_GROUP_EXIT; zap_other_threads(current); } spin_unlock_irq(&sighand->siglock); } do_exit(exit_code); /* NOTREACHED */ } /* * this kills every thread in the thread group. Note that any externally * wait4()-ing process will get the correct exit code - even if this * thread is not the thread group leader. */ SYSCALL_DEFINE1(exit_group, int, error_code) { do_group_exit((error_code & 0xff) << 8); /* NOTREACHED */ return 0; } struct wait_opts { enum pid_type wo_type; int wo_flags; struct pid *wo_pid; struct siginfo __user *wo_info; int __user *wo_stat; struct rusage __user *wo_rusage; wait_queue_t child_wait; int notask_error; }; static inline struct pid *task_pid_type(struct task_struct *task, enum pid_type type) { if (type != PIDTYPE_PID) task = task->group_leader; return task->pids[type].pid; } static int eligible_pid(struct wait_opts *wo, struct task_struct *p) { return wo->wo_type == PIDTYPE_MAX || task_pid_type(p, wo->wo_type) == wo->wo_pid; } static int eligible_child(struct wait_opts *wo, struct task_struct *p) { if (!eligible_pid(wo, p)) return 0; /* Wait for all children (clone and not) if __WALL is set; * otherwise, wait for clone children *only* if __WCLONE is * set; otherwise, wait for non-clone children *only*. (Note: * A "clone" child here is one that reports to its parent * using a signal other than SIGCHLD.) */ if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE)) && !(wo->wo_flags & __WALL)) return 0; return 1; } static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p, pid_t pid, uid_t uid, int why, int status) { struct siginfo __user *infop; int retval = wo->wo_rusage ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0; put_task_struct(p); infop = wo->wo_info; if (infop) { if (!retval) retval = put_user(SIGCHLD, &infop->si_signo); if (!retval) retval = put_user(0, &infop->si_errno); if (!retval) retval = put_user((short)why, &infop->si_code); if (!retval) retval = put_user(pid, &infop->si_pid); if (!retval) retval = put_user(uid, &infop->si_uid); if (!retval) retval = put_user(status, &infop->si_status); } if (!retval) retval = pid; return retval; } /* * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold * read_lock(&tasklist_lock) on entry. If we return zero, we still hold * the lock and this task is uninteresting. If we return nonzero, we have * released the lock and the system call should return. */ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) { unsigned long state; int retval, status, traced; pid_t pid = task_pid_vnr(p); uid_t uid = __task_cred(p)->uid; struct siginfo __user *infop; if (!likely(wo->wo_flags & WEXITED)) return 0; if (unlikely(wo->wo_flags & WNOWAIT)) { int exit_code = p->exit_code; int why; get_task_struct(p); read_unlock(&tasklist_lock); if ((exit_code & 0x7f) == 0) { why = CLD_EXITED; status = exit_code >> 8; } else { why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED; status = exit_code & 0x7f; } return wait_noreap_copyout(wo, p, pid, uid, why, status); } /* * Try to move the task's state to DEAD * only one thread is allowed to do this: */ state = xchg(&p->exit_state, EXIT_DEAD); if (state != EXIT_ZOMBIE) { BUG_ON(state != EXIT_DEAD); return 0; } traced = ptrace_reparented(p); /* * It can be ptraced but not reparented, check * thread_group_leader() to filter out sub-threads. */ if (likely(!traced) && thread_group_leader(p)) { struct signal_struct *psig; struct signal_struct *sig; unsigned long maxrss; cputime_t tgutime, tgstime; /* * The resource counters for the group leader are in its * own task_struct. Those for dead threads in the group * are in its signal_struct, as are those for the child * processes it has previously reaped. All these * accumulate in the parent's signal_struct c* fields. * * We don't bother to take a lock here to protect these * p->signal fields, because they are only touched by * __exit_signal, which runs with tasklist_lock * write-locked anyway, and so is excluded here. We do * need to protect the access to parent->signal fields, * as other threads in the parent group can be right * here reaping other children at the same time. * * We use thread_group_times() to get times for the thread * group, which consolidates times for all threads in the * group including the group leader. */ thread_group_times(p, &tgutime, &tgstime); spin_lock_irq(&p->real_parent->sighand->siglock); psig = p->real_parent->signal; sig = p->signal; psig->cutime = cputime_add(psig->cutime, cputime_add(tgutime, sig->cutime)); psig->cstime = cputime_add(psig->cstime, cputime_add(tgstime, sig->cstime)); psig->cgtime = cputime_add(psig->cgtime, cputime_add(p->gtime, cputime_add(sig->gtime, sig->cgtime))); psig->cmin_flt += p->min_flt + sig->min_flt + sig->cmin_flt; psig->cmaj_flt += p->maj_flt + sig->maj_flt + sig->cmaj_flt; psig->cnvcsw += p->nvcsw + sig->nvcsw + sig->cnvcsw; psig->cnivcsw += p->nivcsw + sig->nivcsw + sig->cnivcsw; psig->cinblock += task_io_get_inblock(p) + sig->inblock + sig->cinblock; psig->coublock += task_io_get_oublock(p) + sig->oublock + sig->coublock; maxrss = max(sig->maxrss, sig->cmaxrss); if (psig->cmaxrss < maxrss) psig->cmaxrss = maxrss; task_io_accounting_add(&psig->ioac, &p->ioac); task_io_accounting_add(&psig->ioac, &sig->ioac); spin_unlock_irq(&p->real_parent->sighand->siglock); } /* * Now we are sure this task is interesting, and no other * thread can reap it because we set its state to EXIT_DEAD. */ read_unlock(&tasklist_lock); retval = wo->wo_rusage ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0; status = (p->signal->flags & SIGNAL_GROUP_EXIT) ? p->signal->group_exit_code : p->exit_code; if (!retval && wo->wo_stat) retval = put_user(status, wo->wo_stat); infop = wo->wo_info; if (!retval && infop) retval = put_user(SIGCHLD, &infop->si_signo); if (!retval && infop) retval = put_user(0, &infop->si_errno); if (!retval && infop) { int why; if ((status & 0x7f) == 0) { why = CLD_EXITED; status >>= 8; } else { why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; status &= 0x7f; } retval = put_user((short)why, &infop->si_code); if (!retval) retval = put_user(status, &infop->si_status); } if (!retval && infop) retval = put_user(pid, &infop->si_pid); if (!retval && infop) retval = put_user(uid, &infop->si_uid); if (!retval) retval = pid; if (traced) { write_lock_irq(&tasklist_lock); /* We dropped tasklist, ptracer could die and untrace */ ptrace_unlink(p); /* * If this is not a sub-thread, notify the parent. * If parent wants a zombie, don't release it now. */ if (thread_group_leader(p) && !do_notify_parent(p, p->exit_signal)) { p->exit_state = EXIT_ZOMBIE; p = NULL; } write_unlock_irq(&tasklist_lock); } if (p != NULL) release_task(p); return retval; } static int *task_stopped_code(struct task_struct *p, bool ptrace) { if (ptrace) { if (task_is_stopped_or_traced(p) && !(p->jobctl & JOBCTL_LISTENING)) return &p->exit_code; } else { if (p->signal->flags & SIGNAL_STOP_STOPPED) return &p->signal->group_exit_code; } return NULL; } /** * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED * @wo: wait options * @ptrace: is the wait for ptrace * @p: task to wait for * * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED. * * CONTEXT: * read_lock(&tasklist_lock), which is released if return value is * non-zero. Also, grabs and releases @p->sighand->siglock. * * RETURNS: * 0 if wait condition didn't exist and search for other wait conditions * should continue. Non-zero return, -errno on failure and @p's pid on * success, implies that tasklist_lock is released and wait condition * search should terminate. */ static int wait_task_stopped(struct wait_opts *wo, int ptrace, struct task_struct *p) { struct siginfo __user *infop; int retval, exit_code, *p_code, why; uid_t uid = 0; /* unneeded, required by compiler */ pid_t pid; /* * Traditionally we see ptrace'd stopped tasks regardless of options. */ if (!ptrace && !(wo->wo_flags & WUNTRACED)) return 0; if (!task_stopped_code(p, ptrace)) return 0; exit_code = 0; spin_lock_irq(&p->sighand->siglock); p_code = task_stopped_code(p, ptrace); if (unlikely(!p_code)) goto unlock_sig; exit_code = *p_code; if (!exit_code) goto unlock_sig; if (!unlikely(wo->wo_flags & WNOWAIT)) *p_code = 0; uid = task_uid(p); unlock_sig: spin_unlock_irq(&p->sighand->siglock); if (!exit_code) return 0; /* * Now we are pretty sure this task is interesting. * Make sure it doesn't get reaped out from under us while we * give up the lock and then examine it below. We don't want to * keep holding onto the tasklist_lock while we call getrusage and * possibly take page faults for user memory. */ get_task_struct(p); pid = task_pid_vnr(p); why = ptrace ? CLD_TRAPPED : CLD_STOPPED; read_unlock(&tasklist_lock); if (unlikely(wo->wo_flags & WNOWAIT)) return wait_noreap_copyout(wo, p, pid, uid, why, exit_code); retval = wo->wo_rusage ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0; if (!retval && wo->wo_stat) retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat); infop = wo->wo_info; if (!retval && infop) retval = put_user(SIGCHLD, &infop->si_signo); if (!retval && infop) retval = put_user(0, &infop->si_errno); if (!retval && infop) retval = put_user((short)why, &infop->si_code); if (!retval && infop) retval = put_user(exit_code, &infop->si_status); if (!retval && infop) retval = put_user(pid, &infop->si_pid); if (!retval && infop) retval = put_user(uid, &infop->si_uid); if (!retval) retval = pid; put_task_struct(p); BUG_ON(!retval); return retval; } /* * Handle do_wait work for one task in a live, non-stopped state. * read_lock(&tasklist_lock) on entry. If we return zero, we still hold * the lock and this task is uninteresting. If we return nonzero, we have * released the lock and the system call should return. */ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) { int retval; pid_t pid; uid_t uid; if (!unlikely(wo->wo_flags & WCONTINUED)) return 0; if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) return 0; spin_lock_irq(&p->sighand->siglock); /* Re-check with the lock held. */ if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) { spin_unlock_irq(&p->sighand->siglock); return 0; } if (!unlikely(wo->wo_flags & WNOWAIT)) p->signal->flags &= ~SIGNAL_STOP_CONTINUED; uid = task_uid(p); spin_unlock_irq(&p->sighand->siglock); pid = task_pid_vnr(p); get_task_struct(p); read_unlock(&tasklist_lock); if (!wo->wo_info) { retval = wo->wo_rusage ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0; put_task_struct(p); if (!retval && wo->wo_stat) retval = put_user(0xffff, wo->wo_stat); if (!retval) retval = pid; } else { retval = wait_noreap_copyout(wo, p, pid, uid, CLD_CONTINUED, SIGCONT); BUG_ON(retval == 0); } return retval; } /* * Consider @p for a wait by @parent. * * -ECHILD should be in ->notask_error before the first call. * Returns nonzero for a final return, when we have unlocked tasklist_lock. * Returns zero if the search for a child should continue; * then ->notask_error is 0 if @p is an eligible child, * or another error from security_task_wait(), or still -ECHILD. */ static int wait_consider_task(struct wait_opts *wo, int ptrace, struct task_struct *p) { int ret = eligible_child(wo, p); if (!ret) return ret; ret = security_task_wait(p); if (unlikely(ret < 0)) { /* * If we have not yet seen any eligible child, * then let this error code replace -ECHILD. * A permission error will give the user a clue * to look for security policy problems, rather * than for mysterious wait bugs. */ if (wo->notask_error) wo->notask_error = ret; return 0; } /* dead body doesn't have much to contribute */ if (unlikely(p->exit_state == EXIT_DEAD)) { /* * But do not ignore this task until the tracer does * wait_task_zombie()->do_notify_parent(). */ if (likely(!ptrace) && unlikely(ptrace_reparented(p))) wo->notask_error = 0; return 0; } /* slay zombie? */ if (p->exit_state == EXIT_ZOMBIE) { /* * A zombie ptracee is only visible to its ptracer. * Notification and reaping will be cascaded to the real * parent when the ptracer detaches. */ if (likely(!ptrace) && unlikely(p->ptrace)) { /* it will become visible, clear notask_error */ wo->notask_error = 0; return 0; } /* we don't reap group leaders with subthreads */ if (!delay_group_leader(p)) return wait_task_zombie(wo, p); /* * Allow access to stopped/continued state via zombie by * falling through. Clearing of notask_error is complex. * * When !@ptrace: * * If WEXITED is set, notask_error should naturally be * cleared. If not, subset of WSTOPPED|WCONTINUED is set, * so, if there are live subthreads, there are events to * wait for. If all subthreads are dead, it's still safe * to clear - this function will be called again in finite * amount time once all the subthreads are released and * will then return without clearing. * * When @ptrace: * * Stopped state is per-task and thus can't change once the * target task dies. Only continued and exited can happen. * Clear notask_error if WCONTINUED | WEXITED. */ if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED))) wo->notask_error = 0; } else { /* * If @p is ptraced by a task in its real parent's group, * hide group stop/continued state when looking at @p as * the real parent; otherwise, a single stop can be * reported twice as group and ptrace stops. * * If a ptracer wants to distinguish the two events for its * own children, it should create a separate process which * takes the role of real parent. */ if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p)) return 0; /* * @p is alive and it's gonna stop, continue or exit, so * there always is something to wait for. */ wo->notask_error = 0; } /* * Wait for stopped. Depending on @ptrace, different stopped state * is used and the two don't interact with each other. */ ret = wait_task_stopped(wo, ptrace, p); if (ret) return ret; /* * Wait for continued. There's only one continued state and the * ptracer can consume it which can confuse the real parent. Don't * use WCONTINUED from ptracer. You don't need or want it. */ return wait_task_continued(wo, p); } /* * Do the work of do_wait() for one thread in the group, @tsk. * * -ECHILD should be in ->notask_error before the first call. * Returns nonzero for a final return, when we have unlocked tasklist_lock. * Returns zero if the search for a child should continue; then * ->notask_error is 0 if there were any eligible children, * or another error from security_task_wait(), or still -ECHILD. */ static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk) { struct task_struct *p; list_for_each_entry(p, &tsk->children, sibling) { int ret = wait_consider_task(wo, 0, p); if (ret) return ret; } return 0; } static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk) { struct task_struct *p; list_for_each_entry(p, &tsk->ptraced, ptrace_entry) { int ret = wait_consider_task(wo, 1, p); if (ret) return ret; } return 0; } static int child_wait_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) { struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait); struct task_struct *p = key; if (!eligible_pid(wo, p)) return 0; if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent) return 0; return default_wake_function(wait, mode, sync, key); } void __wake_up_parent(struct task_struct *p, struct task_struct *parent) { __wake_up_sync_key(&parent->signal->wait_chldexit, TASK_INTERRUPTIBLE, 1, p); } static long do_wait(struct wait_opts *wo) { struct task_struct *tsk; int retval; trace_sched_process_wait(wo->wo_pid); init_waitqueue_func_entry(&wo->child_wait, child_wait_callback); wo->child_wait.private = current; add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); repeat: /* * If there is nothing that can match our critiera just get out. * We will clear ->notask_error to zero if we see any child that * might later match our criteria, even if we are not able to reap * it yet. */ wo->notask_error = -ECHILD; if ((wo->wo_type < PIDTYPE_MAX) && (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type]))) goto notask; set_current_state(TASK_INTERRUPTIBLE); read_lock(&tasklist_lock); tsk = current; do { retval = do_wait_thread(wo, tsk); if (retval) goto end; retval = ptrace_do_wait(wo, tsk); if (retval) goto end; if (wo->wo_flags & __WNOTHREAD) break; } while_each_thread(current, tsk); read_unlock(&tasklist_lock); notask: retval = wo->notask_error; if (!retval && !(wo->wo_flags & WNOHANG)) { retval = -ERESTARTSYS; if (!signal_pending(current)) { schedule(); goto repeat; } } end: __set_current_state(TASK_RUNNING); remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); return retval; } SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, infop, int, options, struct rusage __user *, ru) { struct wait_opts wo; struct pid *pid = NULL; enum pid_type type; long ret; if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED)) return -EINVAL; if (!(options & (WEXITED|WSTOPPED|WCONTINUED))) return -EINVAL; switch (which) { case P_ALL: type = PIDTYPE_MAX; break; case P_PID: type = PIDTYPE_PID; if (upid <= 0) return -EINVAL; break; case P_PGID: type = PIDTYPE_PGID; if (upid <= 0) return -EINVAL; break; default: return -EINVAL; } if (type < PIDTYPE_MAX) pid = find_get_pid(upid); wo.wo_type = type; wo.wo_pid = pid; wo.wo_flags = options; wo.wo_info = infop; wo.wo_stat = NULL; wo.wo_rusage = ru; ret = do_wait(&wo); if (ret > 0) { ret = 0; } else if (infop) { /* * For a WNOHANG return, clear out all the fields * we would set so the user can easily tell the * difference. */ if (!ret) ret = put_user(0, &infop->si_signo); if (!ret) ret = put_user(0, &infop->si_errno); if (!ret) ret = put_user(0, &infop->si_code); if (!ret) ret = put_user(0, &infop->si_pid); if (!ret) ret = put_user(0, &infop->si_uid); if (!ret) ret = put_user(0, &infop->si_status); } put_pid(pid); /* avoid REGPARM breakage on x86: */ asmlinkage_protect(5, ret, which, upid, infop, options, ru); return ret; } SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr, int, options, struct rusage __user *, ru) { struct wait_opts wo; struct pid *pid = NULL; enum pid_type type; long ret; if (options & ~(WNOHANG|WUNTRACED|WCONTINUED| __WNOTHREAD|__WCLONE|__WALL)) return -EINVAL; if (upid == -1) type = PIDTYPE_MAX; else if (upid < 0) { type = PIDTYPE_PGID; pid = find_get_pid(-upid); } else if (upid == 0) { type = PIDTYPE_PGID; pid = get_task_pid(current, PIDTYPE_PGID); } else /* upid > 0 */ { type = PIDTYPE_PID; pid = find_get_pid(upid); } wo.wo_type = type; wo.wo_pid = pid; wo.wo_flags = options | WEXITED; wo.wo_info = NULL; wo.wo_stat = stat_addr; wo.wo_rusage = ru; ret = do_wait(&wo); put_pid(pid); /* avoid REGPARM breakage on x86: */ asmlinkage_protect(4, ret, upid, stat_addr, options, ru); return ret; } #ifdef __ARCH_WANT_SYS_WAITPID /* * sys_waitpid() remains for compatibility. waitpid() should be * implemented by calling sys_wait4() from libc.a. */ SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options) { return sys_wait4(pid, stat_addr, options, NULL); } #endif