/* * 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 extern void sem_exit (void); extern struct task_struct *child_reaper; int getrusage(struct task_struct *, int, struct rusage __user *); static void exit_mm(struct task_struct * tsk); static void __unhash_process(struct task_struct *p) { nr_threads--; detach_pid(p, PIDTYPE_PID); detach_pid(p, PIDTYPE_TGID); if (thread_group_leader(p)) { detach_pid(p, PIDTYPE_PGID); detach_pid(p, PIDTYPE_SID); if (p->pid) __get_cpu_var(process_counts)--; } REMOVE_LINKS(p); } void release_task(struct task_struct * p) { int zap_leader; task_t *leader; struct dentry *proc_dentry; repeat: atomic_dec(&p->user->processes); spin_lock(&p->proc_lock); proc_dentry = proc_pid_unhash(p); write_lock_irq(&tasklist_lock); if (unlikely(p->ptrace)) __ptrace_unlink(p); BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children)); __exit_signal(p); /* * Note that the fastpath in sys_times depends on __exit_signal having * updated the counters before a task is removed from the tasklist of * the process by __unhash_process. */ __unhash_process(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) { BUG_ON(leader->exit_signal == -1); do_notify_parent(leader, leader->exit_signal); /* * 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. * * do_notify_parent() will have marked it self-reaping in * that case. */ zap_leader = (leader->exit_signal == -1); } sched_exit(p); write_unlock_irq(&tasklist_lock); spin_unlock(&p->proc_lock); proc_pid_flush(proc_dentry); release_thread(p); put_task_struct(p); p = leader; if (unlikely(zap_leader)) goto repeat; } /* we are using it only for SMP init */ void unhash_process(struct task_struct *p) { struct dentry *proc_dentry; spin_lock(&p->proc_lock); proc_dentry = proc_pid_unhash(p); write_lock_irq(&tasklist_lock); __unhash_process(p); write_unlock_irq(&tasklist_lock); spin_unlock(&p->proc_lock); proc_pid_flush(proc_dentry); } /* * 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... */ int session_of_pgrp(int pgrp) { struct task_struct *p; int sid = -1; read_lock(&tasklist_lock); do_each_task_pid(pgrp, PIDTYPE_PGID, p) { if (p->signal->session > 0) { sid = p->signal->session; goto out; } } while_each_task_pid(pgrp, PIDTYPE_PGID, p); p = find_task_by_pid(pgrp); if (p) sid = p->signal->session; out: read_unlock(&tasklist_lock); 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(int pgrp, task_t *ignored_task) { struct task_struct *p; int ret = 1; do_each_task_pid(pgrp, PIDTYPE_PGID, p) { if (p == ignored_task || p->exit_state || p->real_parent->pid == 1) continue; if (process_group(p->real_parent) != pgrp && p->real_parent->signal->session == p->signal->session) { ret = 0; break; } } while_each_task_pid(pgrp, PIDTYPE_PGID, p); return ret; /* (sighing) "Often!" */ } int is_orphaned_pgrp(int pgrp) { int retval; read_lock(&tasklist_lock); retval = will_become_orphaned_pgrp(pgrp, NULL); read_unlock(&tasklist_lock); return retval; } static int has_stopped_jobs(int pgrp) { int retval = 0; struct task_struct *p; do_each_task_pid(pgrp, PIDTYPE_PGID, p) { if (p->state != TASK_STOPPED) continue; /* If p is stopped by a debugger on a signal that won't stop it, then don't count p as stopped. This isn't perfect but it's a good approximation. */ if (unlikely (p->ptrace) && p->exit_code != SIGSTOP && p->exit_code != SIGTSTP && p->exit_code != SIGTTOU && p->exit_code != SIGTTIN) continue; retval = 1; break; } while_each_task_pid(pgrp, PIDTYPE_PGID, p); return retval; } /** * reparent_to_init - Reparent the calling kernel thread to the init task. * * If a kernel thread is launched as a result of a system call, or if * it ever exits, it should generally reparent itself to init so that * it 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_init() gives the caller full capabilities. */ static void reparent_to_init(void) { write_lock_irq(&tasklist_lock); ptrace_unlink(current); /* Reparent to init */ REMOVE_LINKS(current); current->parent = child_reaper; current->real_parent = child_reaper; SET_LINKS(current); /* Set the exit signal to SIGCHLD so we signal init on exit */ current->exit_signal = SIGCHLD; if ((current->policy == SCHED_NORMAL || current->policy == SCHED_BATCH) && (task_nice(current) < 0)) set_user_nice(current, 0); /* cpus_allowed? */ /* rt_priority? */ /* signals? */ security_task_reparent_to_init(current); memcpy(current->signal->rlim, init_task.signal->rlim, sizeof(current->signal->rlim)); atomic_inc(&(INIT_USER->__count)); write_unlock_irq(&tasklist_lock); switch_uid(INIT_USER); } void __set_special_pids(pid_t session, pid_t pgrp) { struct task_struct *curr = current->group_leader; if (curr->signal->session != session) { detach_pid(curr, PIDTYPE_SID); curr->signal->session = session; attach_pid(curr, PIDTYPE_SID, session); } if (process_group(curr) != pgrp) { detach_pid(curr, PIDTYPE_PGID); curr->signal->pgrp = pgrp; attach_pid(curr, PIDTYPE_PGID, pgrp); } } void set_special_pids(pid_t session, pid_t pgrp) { write_lock_irq(&tasklist_lock); __set_special_pids(session, pgrp); write_unlock_irq(&tasklist_lock); } /* * Let kernel threads use this to say that they * allow a certain signal (since daemonize() will * have disabled all of them by default). */ int allow_signal(int sig) { if (!valid_signal(sig) || sig < 1) return -EINVAL; spin_lock_irq(¤t->sighand->siglock); sigdelset(¤t->blocked, sig); if (!current->mm) { /* 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); sigaddset(¤t->blocked, sig); 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; struct fs_struct *fs; 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); set_special_pids(1, 1); down(&tty_sem); current->signal->tty = NULL; up(&tty_sem); /* Block and flush all signals */ sigfillset(&blocked); sigprocmask(SIG_BLOCK, &blocked, NULL); flush_signals(current); /* Become as one with the init task */ exit_fs(current); /* current->fs->count--; */ fs = init_task.fs; current->fs = fs; atomic_inc(&fs->count); exit_namespace(current); current->namespace = init_task.namespace; get_namespace(current->namespace); exit_files(current); current->files = init_task.files; atomic_inc(¤t->files->count); reparent_to_init(); } 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. */ fdt = files_fdtable(files); for (;;) { unsigned long set; i = j * __NFDBITS; if (i >= fdt->max_fdset || 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); } 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 fastcall 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. */ fdt = files_fdtable(files); if (fdt == &files->fdtab) fdt->free_files = files; else kmem_cache_free(files_cachep, files); free_fdtable(fdt); } } EXPORT_SYMBOL(put_files_struct); static inline 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); } } void exit_files(struct task_struct *tsk) { __exit_files(tsk); } static inline void __put_fs_struct(struct fs_struct *fs) { /* No need to hold fs->lock if we are killing it */ if (atomic_dec_and_test(&fs->count)) { dput(fs->root); mntput(fs->rootmnt); dput(fs->pwd); mntput(fs->pwdmnt); if (fs->altroot) { dput(fs->altroot); mntput(fs->altrootmnt); } kmem_cache_free(fs_cachep, fs); } } void put_fs_struct(struct fs_struct *fs) { __put_fs_struct(fs); } static inline void __exit_fs(struct task_struct *tsk) { struct fs_struct * fs = tsk->fs; if (fs) { task_lock(tsk); tsk->fs = NULL; task_unlock(tsk); __put_fs_struct(fs); } } void exit_fs(struct task_struct *tsk) { __exit_fs(tsk); } EXPORT_SYMBOL_GPL(exit_fs); /* * 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; mm_release(tsk, mm); if (!mm) return; /* * Serialize with any possible pending coredump. * We must hold mmap_sem around checking core_waiters * and clearing tsk->mm. The core-inducing thread * will increment core_waiters for each thread in the * group with ->mm != NULL. */ down_read(&mm->mmap_sem); if (mm->core_waiters) { up_read(&mm->mmap_sem); down_write(&mm->mmap_sem); if (!--mm->core_waiters) complete(mm->core_startup_done); up_write(&mm->mmap_sem); wait_for_completion(&mm->core_done); down_read(&mm->mmap_sem); } atomic_inc(&mm->mm_count); if (mm != tsk->active_mm) BUG(); /* more a memory barrier than a real lock */ task_lock(tsk); tsk->mm = NULL; up_read(&mm->mmap_sem); enter_lazy_tlb(mm, current); task_unlock(tsk); mmput(mm); } static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper) { /* * Make sure we're not reparenting to ourselves and that * the parent is not a zombie. */ BUG_ON(p == reaper || reaper->exit_state >= EXIT_ZOMBIE); p->real_parent = reaper; } static void reparent_thread(task_t *p, task_t *father, int traced) { if (p->pdeath_signal) /* We already hold the tasklist_lock here. */ group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p); /* Move the child from its dying parent to the new one. */ if (unlikely(traced)) { /* Preserve ptrace links if someone else is tracing this child. */ list_del_init(&p->ptrace_list); if (p->parent != p->real_parent) list_add(&p->ptrace_list, &p->real_parent->ptrace_children); } else { /* If this child is being traced, then we're the one tracing it * anyway, so let go of it. */ p->ptrace = 0; list_del_init(&p->sibling); p->parent = p->real_parent; list_add_tail(&p->sibling, &p->parent->children); if (p->state == TASK_TRACED) { /* * If it was at a trace stop, turn it into * a normal stop since it's no longer being * traced. */ ptrace_untrace(p); } } /* If this is a threaded reparent there is no need to * notify anyone anything has happened. */ if (p->real_parent->group_leader == father->group_leader) return; /* We don't want people slaying init. */ if (p->exit_signal != -1) p->exit_signal = SIGCHLD; /* If we'd notified the old parent about this child's death, * also notify the new parent. */ if (!traced && p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 && thread_group_empty(p)) do_notify_parent(p, p->exit_signal); /* * process group orphan check * Case ii: Our child is in a different pgrp * than we are, and it was the only connection * outside, so the child pgrp is now orphaned. */ if ((process_group(p) != process_group(father)) && (p->signal->session == father->signal->session)) { int pgrp = process_group(p); if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) { __kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp); __kill_pg_info(SIGCONT, SEND_SIG_PRIV, pgrp); } } } /* * 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 global child reaper process (ie "init") */ static void forget_original_parent(struct task_struct * father, struct list_head *to_release) { struct task_struct *p, *reaper = father; struct list_head *_p, *_n; do { reaper = next_thread(reaper); if (reaper == father) { reaper = child_reaper; break; } } while (reaper->exit_state); /* * There are only two places where our children can be: * * - in our child list * - in our ptraced child list * * Search them and reparent children. */ list_for_each_safe(_p, _n, &father->children) { int ptrace; p = list_entry(_p,struct task_struct,sibling); ptrace = p->ptrace; /* if father isn't the real parent, then ptrace must be enabled */ BUG_ON(father != p->real_parent && !ptrace); if (father == p->real_parent) { /* reparent with a reaper, real father it's us */ choose_new_parent(p, reaper, child_reaper); reparent_thread(p, father, 0); } else { /* reparent ptraced task to its real parent */ __ptrace_unlink (p); if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 && thread_group_empty(p)) do_notify_parent(p, p->exit_signal); } /* * if the ptraced child is a zombie with exit_signal == -1 * we must collect it before we exit, or it will remain * zombie forever since we prevented it from self-reap itself * while it was being traced by us, to be able to see it in wait4. */ if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1)) list_add(&p->ptrace_list, to_release); } list_for_each_safe(_p, _n, &father->ptrace_children) { p = list_entry(_p,struct task_struct,ptrace_list); choose_new_parent(p, reaper, child_reaper); reparent_thread(p, father, 1); } } /* * Send signals to all our closest relatives so that they know * to properly mourn us.. */ static void exit_notify(struct task_struct *tsk) { int state; struct task_struct *t; struct list_head ptrace_dead, *_p, *_n; if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT) && !thread_group_empty(tsk)) { /* * This occurs when there was a race between our exit * syscall and a group signal choosing us as the one to * wake up. It could be that we are the only thread * alerted to check for pending signals, but another thread * should be woken now to take the signal since we will not. * Now we'll wake all the threads in the group just to make * sure someone gets all the pending signals. */ read_lock(&tasklist_lock); spin_lock_irq(&tsk->sighand->siglock); for (t = next_thread(tsk); t != tsk; t = next_thread(t)) if (!signal_pending(t) && !(t->flags & PF_EXITING)) { recalc_sigpending_tsk(t); if (signal_pending(t)) signal_wake_up(t, 0); } spin_unlock_irq(&tsk->sighand->siglock); read_unlock(&tasklist_lock); } write_lock_irq(&tasklist_lock); /* * 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) */ INIT_LIST_HEAD(&ptrace_dead); forget_original_parent(tsk, &ptrace_dead); BUG_ON(!list_empty(&tsk->children)); BUG_ON(!list_empty(&tsk->ptrace_children)); /* * 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) * * Case i: Our father is in a different pgrp than we are * and we were the only connection outside, so our pgrp * is about to become orphaned. */ t = tsk->real_parent; if ((process_group(t) != process_group(tsk)) && (t->signal->session == tsk->signal->session) && will_become_orphaned_pgrp(process_group(tsk), tsk) && has_stopped_jobs(process_group(tsk))) { __kill_pg_info(SIGHUP, SEND_SIG_PRIV, process_group(tsk)); __kill_pg_info(SIGCONT, SEND_SIG_PRIV, process_group(tsk)); } /* Let father know we died * * Thread signals are configurable, but you aren't going to use * that to send signals to arbitary processes. * That stops right now. * * If the parent exec id doesn't match the exec id we saved * when we started then we know the parent has changed security * domain. * * If our self_exec id doesn't match our parent_exec_id then * we have changed execution domain as these two values started * the same after a fork. * */ if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 && ( tsk->parent_exec_id != t->self_exec_id || tsk->self_exec_id != tsk->parent_exec_id) && !capable(CAP_KILL)) tsk->exit_signal = SIGCHLD; /* If something other than our normal parent is ptracing us, then * send it a SIGCHLD instead of honoring exit_signal. exit_signal * only has special meaning to our real parent. */ if (tsk->exit_signal != -1 && thread_group_empty(tsk)) { int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD; do_notify_parent(tsk, signal); } else if (tsk->ptrace) { do_notify_parent(tsk, SIGCHLD); } state = EXIT_ZOMBIE; if (tsk->exit_signal == -1 && (likely(tsk->ptrace == 0) || unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT))) state = EXIT_DEAD; tsk->exit_state = state; write_unlock_irq(&tasklist_lock); list_for_each_safe(_p, _n, &ptrace_dead) { list_del_init(_p); t = list_entry(_p,struct task_struct,ptrace_list); release_task(t); } /* If the process is dead, release it - nobody will wait for it */ if (state == EXIT_DEAD) release_task(tsk); } fastcall NORET_TYPE void do_exit(long code) { struct task_struct *tsk = current; int group_dead; profile_task_exit(tsk); WARN_ON(atomic_read(&tsk->fs_excl)); if (unlikely(in_interrupt())) panic("Aiee, killing interrupt handler!"); if (unlikely(!tsk->pid)) panic("Attempted to kill the idle task!"); if (unlikely(tsk->pid == 1)) panic("Attempted to kill init!"); if (tsk->io_context) exit_io_context(); if (unlikely(current->ptrace & PT_TRACE_EXIT)) { current->ptrace_message = code; ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP); } /* * 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"); set_current_state(TASK_UNINTERRUPTIBLE); schedule(); } tsk->flags |= PF_EXITING; if (unlikely(in_atomic())) printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n", current->comm, current->pid, preempt_count()); acct_update_integrals(tsk); if (tsk->mm) { update_hiwater_rss(tsk->mm); update_hiwater_vm(tsk->mm); } group_dead = atomic_dec_and_test(&tsk->signal->live); if (group_dead) { hrtimer_cancel(&tsk->signal->real_timer); exit_itimers(tsk->signal); acct_process(code); } exit_mm(tsk); exit_sem(tsk); __exit_files(tsk); __exit_fs(tsk); exit_namespace(tsk); exit_thread(); cpuset_exit(tsk); exit_keys(tsk); if (group_dead && tsk->signal->leader) disassociate_ctty(1); module_put(task_thread_info(tsk)->exec_domain->module); if (tsk->binfmt) module_put(tsk->binfmt->module); tsk->exit_code = code; proc_exit_connector(tsk); exit_notify(tsk); #ifdef CONFIG_NUMA mpol_free(tsk->mempolicy); tsk->mempolicy = NULL; #endif /* * If DEBUG_MUTEXES is on, make sure we are holding no locks: */ mutex_debug_check_no_locks_held(tsk); /* PF_DEAD causes final put_task_struct after we schedule. */ preempt_disable(); BUG_ON(tsk->flags & PF_DEAD); tsk->flags |= PF_DEAD; schedule(); BUG(); /* Avoid "noreturn function does return". */ for (;;) ; } 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); asmlinkage long sys_exit(int error_code) { do_exit((error_code&0xff)<<8); } task_t fastcall *next_thread(const task_t *p) { return pid_task(p->pids[PIDTYPE_TGID].pid_list.next, PIDTYPE_TGID); } EXPORT_SYMBOL(next_thread); /* * 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) { BUG_ON(exit_code & 0x80); /* core dumps don't get here */ if (current->signal->flags & SIGNAL_GROUP_EXIT) exit_code = current->signal->group_exit_code; else if (!thread_group_empty(current)) { struct signal_struct *const sig = current->signal; struct sighand_struct *const sighand = current->sighand; read_lock(&tasklist_lock); spin_lock_irq(&sighand->siglock); if (sig->flags & SIGNAL_GROUP_EXIT) /* Another thread got here before we took the lock. */ exit_code = sig->group_exit_code; else { sig->group_exit_code = exit_code; zap_other_threads(current); } spin_unlock_irq(&sighand->siglock); read_unlock(&tasklist_lock); } 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. */ asmlinkage void sys_exit_group(int error_code) { do_group_exit((error_code & 0xff) << 8); } static int eligible_child(pid_t pid, int options, task_t *p) { if (pid > 0) { if (p->pid != pid) return 0; } else if (!pid) { if (process_group(p) != process_group(current)) return 0; } else if (pid != -1) { if (process_group(p) != -pid) return 0; } /* * Do not consider detached threads that are * not ptraced: */ if (p->exit_signal == -1 && !p->ptrace) 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) ^ ((options & __WCLONE) != 0)) && !(options & __WALL)) return 0; /* * Do not consider thread group leaders that are * in a non-empty thread group: */ if (current->tgid != p->tgid && delay_group_leader(p)) return 2; if (security_task_wait(p)) return 0; return 1; } static int wait_noreap_copyout(task_t *p, pid_t pid, uid_t uid, int why, int status, struct siginfo __user *infop, struct rusage __user *rusagep) { int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0; put_task_struct(p); 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(task_t *p, int noreap, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { unsigned long state; int retval; int status; if (unlikely(noreap)) { pid_t pid = p->pid; uid_t uid = p->uid; int exit_code = p->exit_code; int why, status; if (unlikely(p->exit_state != EXIT_ZOMBIE)) return 0; if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) return 0; 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(p, pid, uid, why, status, infop, ru); } /* * 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; } if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) { /* * This can only happen in a race with a ptraced thread * dying on another processor. */ return 0; } if (likely(p->real_parent == p->parent) && likely(p->signal)) { struct signal_struct *psig; struct signal_struct *sig; /* * 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 p->parent->signal fields, * as other threads in the parent group can be right * here reaping other children at the same time. */ spin_lock_irq(&p->parent->sighand->siglock); psig = p->parent->signal; sig = p->signal; psig->cutime = cputime_add(psig->cutime, cputime_add(p->utime, cputime_add(sig->utime, sig->cutime))); psig->cstime = cputime_add(psig->cstime, cputime_add(p->stime, cputime_add(sig->stime, sig->cstime))); 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; spin_unlock_irq(&p->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 = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0; status = (p->signal->flags & SIGNAL_GROUP_EXIT) ? p->signal->group_exit_code : p->exit_code; if (!retval && stat_addr) retval = put_user(status, stat_addr); 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(p->pid, &infop->si_pid); if (!retval && infop) retval = put_user(p->uid, &infop->si_uid); if (retval) { // TODO: is this safe? p->exit_state = EXIT_ZOMBIE; return retval; } retval = p->pid; if (p->real_parent != p->parent) { write_lock_irq(&tasklist_lock); /* Double-check with lock held. */ if (p->real_parent != p->parent) { __ptrace_unlink(p); // TODO: is this safe? p->exit_state = EXIT_ZOMBIE; /* * If this is not a detached task, notify the parent. * If it's still not detached after that, don't release * it now. */ if (p->exit_signal != -1) { do_notify_parent(p, p->exit_signal); if (p->exit_signal != -1) p = NULL; } } write_unlock_irq(&tasklist_lock); } if (p != NULL) release_task(p); BUG_ON(!retval); return retval; } /* * Handle sys_wait4 work for one task in state TASK_STOPPED. 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_stopped(task_t *p, int delayed_group_leader, int noreap, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { int retval, exit_code; if (!p->exit_code) return 0; if (delayed_group_leader && !(p->ptrace & PT_PTRACED) && p->signal && p->signal->group_stop_count > 0) /* * A group stop is in progress and this is the group leader. * We won't report until all threads have stopped. */ 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); read_unlock(&tasklist_lock); if (unlikely(noreap)) { pid_t pid = p->pid; uid_t uid = p->uid; int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED; exit_code = p->exit_code; if (unlikely(!exit_code) || unlikely(p->exit_state)) goto bail_ref; return wait_noreap_copyout(p, pid, uid, why, (exit_code << 8) | 0x7f, infop, ru); } write_lock_irq(&tasklist_lock); /* * This uses xchg to be atomic with the thread resuming and setting * it. It must also be done with the write lock held to prevent a * race with the EXIT_ZOMBIE case. */ exit_code = xchg(&p->exit_code, 0); if (unlikely(p->exit_state)) { /* * The task resumed and then died. Let the next iteration * catch it in EXIT_ZOMBIE. Note that exit_code might * already be zero here if it resumed and did _exit(0). * The task itself is dead and won't touch exit_code again; * other processors in this function are locked out. */ p->exit_code = exit_code; exit_code = 0; } if (unlikely(exit_code == 0)) { /* * Another thread in this function got to it first, or it * resumed, or it resumed and then died. */ write_unlock_irq(&tasklist_lock); bail_ref: put_task_struct(p); /* * We are returning to the wait loop without having successfully * removed the process and having released the lock. We cannot * continue, since the "p" task pointer is potentially stale. * * Return -EAGAIN, and do_wait() will restart the loop from the * beginning. Do _not_ re-acquire the lock. */ return -EAGAIN; } /* move to end of parent's list to avoid starvation */ remove_parent(p); add_parent(p, p->parent); write_unlock_irq(&tasklist_lock); retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0; if (!retval && stat_addr) retval = put_user((exit_code << 8) | 0x7f, stat_addr); 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)((p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED), &infop->si_code); if (!retval && infop) retval = put_user(exit_code, &infop->si_status); if (!retval && infop) retval = put_user(p->pid, &infop->si_pid); if (!retval && infop) retval = put_user(p->uid, &infop->si_uid); if (!retval) retval = p->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(task_t *p, int noreap, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { int retval; pid_t pid; uid_t uid; if (unlikely(!p->signal)) 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 (!noreap) p->signal->flags &= ~SIGNAL_STOP_CONTINUED; spin_unlock_irq(&p->sighand->siglock); pid = p->pid; uid = p->uid; get_task_struct(p); read_unlock(&tasklist_lock); if (!infop) { retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0; put_task_struct(p); if (!retval && stat_addr) retval = put_user(0xffff, stat_addr); if (!retval) retval = p->pid; } else { retval = wait_noreap_copyout(p, pid, uid, CLD_CONTINUED, SIGCONT, infop, ru); BUG_ON(retval == 0); } return retval; } static inline int my_ptrace_child(struct task_struct *p) { if (!(p->ptrace & PT_PTRACED)) return 0; if (!(p->ptrace & PT_ATTACHED)) return 1; /* * This child was PTRACE_ATTACH'd. We should be seeing it only if * we are the attacher. If we are the real parent, this is a race * inside ptrace_attach. It is waiting for the tasklist_lock, * which we have to switch the parent links, but has already set * the flags in p->ptrace. */ return (p->parent != p->real_parent); } static long do_wait(pid_t pid, int options, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { DECLARE_WAITQUEUE(wait, current); struct task_struct *tsk; int flag, retval; add_wait_queue(¤t->signal->wait_chldexit,&wait); repeat: /* * We will set this flag if we see any child that might later * match our criteria, even if we are not able to reap it yet. */ flag = 0; current->state = TASK_INTERRUPTIBLE; read_lock(&tasklist_lock); tsk = current; do { struct task_struct *p; struct list_head *_p; int ret; list_for_each(_p,&tsk->children) { p = list_entry(_p,struct task_struct,sibling); ret = eligible_child(pid, options, p); if (!ret) continue; switch (p->state) { case TASK_TRACED: /* * When we hit the race with PTRACE_ATTACH, * we will not report this child. But the * race means it has not yet been moved to * our ptrace_children list, so we need to * set the flag here to avoid a spurious ECHILD * when the race happens with the only child. */ flag = 1; if (!my_ptrace_child(p)) continue; /*FALLTHROUGH*/ case TASK_STOPPED: /* * It's stopped now, so it might later * continue, exit, or stop again. */ flag = 1; if (!(options & WUNTRACED) && !my_ptrace_child(p)) continue; retval = wait_task_stopped(p, ret == 2, (options & WNOWAIT), infop, stat_addr, ru); if (retval == -EAGAIN) goto repeat; if (retval != 0) /* He released the lock. */ goto end; break; default: // case EXIT_DEAD: if (p->exit_state == EXIT_DEAD) continue; // case EXIT_ZOMBIE: if (p->exit_state == EXIT_ZOMBIE) { /* * Eligible but we cannot release * it yet: */ if (ret == 2) goto check_continued; if (!likely(options & WEXITED)) continue; retval = wait_task_zombie( p, (options & WNOWAIT), infop, stat_addr, ru); /* He released the lock. */ if (retval != 0) goto end; break; } check_continued: /* * It's running now, so it might later * exit, stop, or stop and then continue. */ flag = 1; if (!unlikely(options & WCONTINUED)) continue; retval = wait_task_continued( p, (options & WNOWAIT), infop, stat_addr, ru); if (retval != 0) /* He released the lock. */ goto end; break; } } if (!flag) { list_for_each(_p, &tsk->ptrace_children) { p = list_entry(_p, struct task_struct, ptrace_list); if (!eligible_child(pid, options, p)) continue; flag = 1; break; } } if (options & __WNOTHREAD) break; tsk = next_thread(tsk); if (tsk->signal != current->signal) BUG(); } while (tsk != current); read_unlock(&tasklist_lock); if (flag) { retval = 0; if (options & WNOHANG) goto end; retval = -ERESTARTSYS; if (signal_pending(current)) goto end; schedule(); goto repeat; } retval = -ECHILD; end: current->state = TASK_RUNNING; remove_wait_queue(¤t->signal->wait_chldexit,&wait); if (infop) { if (retval > 0) retval = 0; else { /* * For a WNOHANG return, clear out all the fields * we would set so the user can easily tell the * difference. */ if (!retval) retval = put_user(0, &infop->si_signo); if (!retval) retval = put_user(0, &infop->si_errno); if (!retval) retval = put_user(0, &infop->si_code); if (!retval) retval = put_user(0, &infop->si_pid); if (!retval) retval = put_user(0, &infop->si_uid); if (!retval) retval = put_user(0, &infop->si_status); } } return retval; } asmlinkage long sys_waitid(int which, pid_t pid, struct siginfo __user *infop, int options, struct rusage __user *ru) { long ret; if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED)) return -EINVAL; if (!(options & (WEXITED|WSTOPPED|WCONTINUED))) return -EINVAL; switch (which) { case P_ALL: pid = -1; break; case P_PID: if (pid <= 0) return -EINVAL; break; case P_PGID: if (pid <= 0) return -EINVAL; pid = -pid; break; default: return -EINVAL; } ret = do_wait(pid, options, infop, NULL, ru); /* avoid REGPARM breakage on x86: */ prevent_tail_call(ret); return ret; } asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr, int options, struct rusage __user *ru) { long ret; if (options & ~(WNOHANG|WUNTRACED|WCONTINUED| __WNOTHREAD|__WCLONE|__WALL)) return -EINVAL; ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru); /* avoid REGPARM breakage on x86: */ prevent_tail_call(ret); return ret; } #ifdef __ARCH_WANT_SYS_WAITPID /* * sys_waitpid() remains for compatibility. waitpid() should be * implemented by calling sys_wait4() from libc.a. */ asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options) { return sys_wait4(pid, stat_addr, options, NULL); } #endif