Fedora kernel-2.6.17-1.2142_FC4 patched with stable patch-2.6.17.4-vs2.0.2-rc26.diff
[linux-2.6.git] / kernel / exit.c
index c84802f..fedcdea 100644 (file)
@@ -10,6 +10,7 @@
 #include <linux/interrupt.h>
 #include <linux/smp_lock.h>
 #include <linux/module.h>
+#include <linux/capability.h>
 #include <linux/completion.h>
 #include <linux/personality.h>
 #include <linux/tty.h>
 #include <linux/cpuset.h>
 #include <linux/syscalls.h>
 #include <linux/signal.h>
+#include <linux/posix-timers.h>
+#include <linux/cn_proc.h>
+#include <linux/mutex.h>
+#include <linux/futex.h>
+#include <linux/compat.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/audit.h> /* for audit_free() */
 #include <linux/vs_limit.h>
+#include <linux/vs_context.h>
 #include <linux/vs_network.h>
+#include <linux/vs_cvirt.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -46,21 +56,86 @@ static void exit_mm(struct task_struct * tsk);
 static void __unhash_process(struct task_struct *p)
 {
        nr_threads--;
-       /* tasklist_lock is held, is this sufficient? */
-       if (p->vx_info) {
-               atomic_dec(&p->vx_info->cvirt.nr_threads);
-               vx_nproc_dec(p);
-       }
        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)--;
+
+               list_del_rcu(&p->tasks);
+               __get_cpu_var(process_counts)--;
        }
+       list_del_rcu(&p->thread_group);
+       remove_parent(p);
+}
 
-       REMOVE_LINKS(p);
+/*
+ * This function expects the tasklist_lock write-locked.
+ */
+static void __exit_signal(struct task_struct *tsk)
+{
+       struct signal_struct *sig = tsk->signal;
+       struct sighand_struct *sighand;
+
+       BUG_ON(!sig);
+       BUG_ON(!atomic_read(&sig->count));
+
+       rcu_read_lock();
+       sighand = rcu_dereference(tsk->sighand);
+       spin_lock(&sighand->siglock);
+
+       posix_cpu_timers_exit(tsk);
+       if (atomic_dec_and_test(&sig->count))
+               posix_cpu_timers_exit_group(tsk);
+       else {
+               /*
+                * If there is any task waiting for the group exit
+                * then notify it:
+                */
+               if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
+                       wake_up_process(sig->group_exit_task);
+                       sig->group_exit_task = NULL;
+               }
+               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->min_flt += tsk->min_flt;
+               sig->maj_flt += tsk->maj_flt;
+               sig->nvcsw += tsk->nvcsw;
+               sig->nivcsw += tsk->nivcsw;
+               sig->sched_time += tsk->sched_time;
+               sig = NULL; /* Marker for below. */
+       }
+
+       __unhash_process(tsk);
+
+       tsk->signal = NULL;
+       tsk->sighand = NULL;
+       spin_unlock(&sighand->siglock);
+       rcu_read_unlock();
+
+       __cleanup_sighand(sighand);
+       clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
+       flush_sigqueue(&tsk->pending);
+       if (sig) {
+               flush_sigqueue(&sig->shared_pending);
+               __cleanup_signal(sig);
+       }
+}
+
+static void delayed_put_task_struct(struct rcu_head *rhp)
+{
+       put_task_struct(container_of(rhp, struct task_struct, rcu));
 }
 
 void release_task(struct task_struct * p)
@@ -69,17 +144,14 @@ void release_task(struct task_struct * p)
        task_t *leader;
        struct dentry *proc_dentry;
 
-repeat: 
+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);
+       ptrace_unlink(p);
        BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
        __exit_signal(p);
-       __exit_sighand(p);
-       __unhash_process(p);
 
        /*
         * If we are the last non-leader member of the thread
@@ -107,32 +179,13 @@ repeat:
        spin_unlock(&p->proc_lock);
        proc_pid_flush(proc_dentry);
        release_thread(p);
-       if (p->vx_info)
-               release_vx_info(p->vx_info, p);
-       if (p->nx_info)
-               release_nx_info(p->nx_info, p);
-       put_task_struct(p);
+       call_rcu(&p->rcu, delayed_put_task_struct);
 
        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
@@ -197,7 +250,7 @@ int is_orphaned_pgrp(int pgrp)
        return retval;
 }
 
-static inline int has_stopped_jobs(int pgrp)
+static int has_stopped_jobs(int pgrp)
 {
        int retval = 0;
        struct task_struct *p;
@@ -234,22 +287,24 @@ static inline int has_stopped_jobs(int pgrp)
  *
  * NOTE that reparent_to_init() gives the caller full capabilities.
  */
-static inline void reparent_to_init(void)
+static void reparent_to_init(void)
 {
        write_lock_irq(&tasklist_lock);
 
        ptrace_unlink(current);
        /* Reparent to init */
-       REMOVE_LINKS(current);
-       /* FIXME handle vchild_reaper/initpid */
+       remove_parent(current);
+       /* FIXME: handle vchild_reaper/initpid */
        current->parent = child_reaper;
        current->real_parent = child_reaper;
-       SET_LINKS(current);
+       add_parent(current);
 
        /* Set the exit signal to SIGCHLD so we signal init on exit */
        current->exit_signal = SIGCHLD;
 
-       if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
+       if ((current->policy == SCHED_NORMAL ||
+                       current->policy == SCHED_BATCH)
+                               && (task_nice(current) < 0))
                set_user_nice(current, 0);
        /* cpus_allowed? */
        /* rt_priority? */
@@ -264,7 +319,7 @@ static inline void reparent_to_init(void)
 
 void __set_special_pids(pid_t session, pid_t pgrp)
 {
-       struct task_struct *curr = current;
+       struct task_struct *curr = current->group_leader;
 
        if (curr->signal->session != session) {
                detach_pid(curr, PIDTYPE_SID);
@@ -348,9 +403,9 @@ void daemonize(const char *name, ...)
        exit_mm(current);
 
        set_special_pids(1, 1);
-       down(&tty_sem);
+       mutex_lock(&tty_mutex);
        current->signal->tty = NULL;
-       up(&tty_sem);
+       mutex_unlock(&tty_mutex);
 
        /* Block and flush all signals */
        sigfillset(&blocked);
@@ -363,6 +418,9 @@ void daemonize(const char *name, ...)
        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(&current->files->count);
@@ -372,20 +430,28 @@ void daemonize(const char *name, ...)
 
 EXPORT_SYMBOL(daemonize);
 
-static inline void close_files(struct files_struct * files)
+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 >= files->max_fdset || i >= files->max_fds)
+               if (i >= fdt->max_fdset || i >= fdt->max_fds)
                        break;
-               set = files->open_fds->fds_bits[j++];
+               set = fdt->open_fds->fds_bits[j++];
                while (set) {
                        if (set & 1) {
-                               struct file * file = xchg(&files->fd[i], NULL);
+                               struct file * file = xchg(&fdt->fd[i], NULL);
                                if (file)
                                        filp_close(file, files);
                                vx_openfd_dec(i);
@@ -411,18 +477,22 @@ struct files_struct *get_files_struct(struct task_struct *task)
 
 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.
                 */
-               if (files->fd != &files->fd_array[0])
-                       free_fd_array(files->fd, files->max_fds);
-               if (files->max_fdset > __FD_SETSIZE) {
-                       free_fdset(files->open_fds, files->max_fdset);
-                       free_fdset(files->close_on_exec, files->max_fdset);
-               }
-               kmem_cache_free(files_cachep, files);
+               fdt = files_fdtable(files);
+               if (fdt == &files->fdtab)
+                       fdt->free_files = files;
+               else
+                       kmem_cache_free(files_cachep, files);
+               free_fdtable(fdt);
        }
 }
 
@@ -525,17 +595,22 @@ static void exit_mm(struct task_struct * tsk)
        mmput(mm);
 }
 
-static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper)
+static inline void choose_new_parent(task_t *p, task_t *reaper)
 {
+       /* check for reaper context */
+       vxwprintk((p->xid != reaper->xid) && (reaper != child_reaper),
+               "rogue reaper: %p[%d,#%u] <> %p[%d,#%u]",
+               p, p->pid, p->xid, reaper, reaper->pid, reaper->xid);
+
        /*
         * 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);
+       BUG_ON(p == reaper || reaper->exit_state);
        p->real_parent = reaper;
 }
 
-static inline void reparent_thread(task_t *p, task_t *father, int traced)
+static void reparent_thread(task_t *p, task_t *father, int traced)
 {
        /* We don't want people slaying init.  */
        if (p->exit_signal != -1)
@@ -543,7 +618,7 @@ static inline 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, (void *) 0, p);
+               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)) {
@@ -556,9 +631,9 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
                 * anyway, so let go of it.
                 */
                p->ptrace = 0;
-               list_del_init(&p->sibling);
+               remove_parent(p);
                p->parent = p->real_parent;
-               list_add_tail(&p->sibling, &p->parent->children);
+               add_parent(p);
 
                /* If we'd notified the old parent about this child's death,
                 * also notify the new parent.
@@ -587,8 +662,8 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
                int pgrp = process_group(p);
 
                if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
-                       __kill_pg_info(SIGHUP, (void *)1, pgrp);
-                       __kill_pg_info(SIGCONT, (void *)1, pgrp);
+                       __kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp);
+                       __kill_pg_info(SIGCONT, SEND_SIG_PRIV, pgrp);
                }
        }
 }
@@ -599,17 +674,16 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
  * group, and if no such member exists, give it to
  * the global child reaper process (ie "init")
  */
-static inline void forget_original_parent(struct task_struct * father,
+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;
 
-       /* FIXME handle vchild_reaper/initpid */
        do {
                reaper = next_thread(reaper);
                if (reaper == father) {
-                       reaper = child_reaper;
+                       reaper = vx_child_reaper(father);
                        break;
                }
        } while (reaper->exit_state);
@@ -633,7 +707,7 @@ static inline void forget_original_parent(struct task_struct * father,
 
                if (father == p->real_parent) {
                        /* reparent with a reaper, real father it's us */
-                       choose_new_parent(p, reaper, child_reaper);
+                       choose_new_parent(p, vx_child_reaper(p));
                        reparent_thread(p, father, 0);
                } else {
                        /* reparent ptraced task to its real parent */
@@ -654,7 +728,8 @@ static inline void forget_original_parent(struct task_struct * father,
        }
        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);
+               /* check for reaper context */
+               choose_new_parent(p, reaper);
                reparent_thread(p, father, 1);
        }
 }
@@ -724,8 +799,8 @@ static void exit_notify(struct task_struct *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, (void *)1, process_group(tsk));
-               __kill_pg_info(SIGCONT, (void *)1, 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 
@@ -780,10 +855,6 @@ static void exit_notify(struct task_struct *tsk)
        /* If the process is dead, release it - nobody will wait for it */
        if (state == EXIT_DEAD)
                release_task(tsk);
-
-       /* PF_DEAD causes final put_task_struct after we schedule. */
-       preempt_disable();
-       tsk->flags |= PF_DEAD;
 }
 
 fastcall NORET_TYPE void do_exit(long code)
@@ -793,29 +864,34 @@ fastcall NORET_TYPE void do_exit(long code)
 
        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))
+       if (unlikely(tsk == child_reaper))
                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);
        }
 
-       tsk->flags |= PF_EXITING;
-
        /*
-        * Make sure we don't try to process any timer firings
-        * while we are already exiting.
+        * We're taking recursive faults here in do_exit. Safest is to just
+        * leave this task alone and wait for reboot.
         */
-       tsk->it_virt_expires = cputime_zero;
-       tsk->it_prof_expires = cputime_zero;
-       tsk->it_sched_expires = 0;
+       if (unlikely(tsk->flags & PF_EXITING)) {
+               printk(KERN_ALERT
+                       "Fixing recursive fault but reboot is needed!\n");
+               if (tsk->io_context)
+                       exit_io_context();
+               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",
@@ -823,16 +899,39 @@ fastcall NORET_TYPE void do_exit(long code)
                                preempt_count());
 
        acct_update_integrals(tsk);
-       update_mem_hiwater(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)
+       if (group_dead) {
+               hrtimer_cancel(&tsk->signal->real_timer);
+               exit_itimers(tsk->signal);
                acct_process(code);
+               if (current->tux_info) {
+#ifdef CONFIG_TUX_DEBUG
+                       printk("Possibly unexpected TUX-thread exit(%ld) at %p?\n",
+                               code, __builtin_return_address(0));
+#endif
+                       current->tux_exit();
+               }
+       }
+       if (unlikely(tsk->robust_list))
+               exit_robust_list(tsk);
+#if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
+       if (unlikely(tsk->compat_robust_list))
+               compat_exit_robust_list(tsk);
+#endif
+       if (unlikely(tsk->audit_context))
+               audit_free(tsk);
        exit_mm(tsk);
 
        exit_sem(tsk);
        __exit_files(tsk);
        __exit_fs(tsk);
        exit_namespace(tsk);
+       exit_vx_info(tsk, code);
+       exit_nx_info(tsk);
        exit_thread();
        cpuset_exit(tsk);
        exit_keys(tsk);
@@ -840,18 +939,33 @@ fastcall NORET_TYPE void do_exit(long code)
        if (group_dead && tsk->signal->leader)
                disassociate_ctty(1);
 
-       module_put(tsk->thread_info->exec_domain->module);
+       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);
+
+       if (tsk->io_context)
+               exit_io_context();
+
+       if (tsk->splice_pipe)
+               __free_pipe_info(tsk->splice_pipe);
+
+       /* PF_DEAD causes final put_task_struct after we schedule. */
+       preempt_disable();
+       BUG_ON(tsk->flags & PF_DEAD);
+       tsk->flags |= PF_DEAD;
 
-       BUG_ON(!(current->flags & PF_DEAD));
        schedule();
        BUG();
        /* Avoid "noreturn function does return".  */
@@ -875,13 +989,6 @@ 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).
@@ -896,18 +1003,15 @@ do_group_exit(int 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->flags = SIGNAL_GROUP_EXIT;
                        sig->group_exit_code = exit_code;
                        zap_other_threads(current);
                }
                spin_unlock_irq(&sighand->siglock);
-               read_unlock(&tasklist_lock);
        }
 
        do_exit(exit_code);
@@ -1044,6 +1148,9 @@ static int wait_task_zombie(task_t *p, int noreap,
        }
 
        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
@@ -1060,24 +1167,26 @@ static int wait_task_zombie(task_t *p, int noreap,
                 * here reaping other children at the same time.
                 */
                spin_lock_irq(&p->parent->sighand->siglock);
-               p->parent->signal->cutime =
-                       cputime_add(p->parent->signal->cutime,
+               psig = p->parent->signal;
+               sig = p->signal;
+               psig->cutime =
+                       cputime_add(psig->cutime,
                        cputime_add(p->utime,
-                       cputime_add(p->signal->utime,
-                                   p->signal->cutime)));
-               p->parent->signal->cstime =
-                       cputime_add(p->parent->signal->cstime,
+                       cputime_add(sig->utime,
+                                   sig->cutime)));
+               psig->cstime =
+                       cputime_add(psig->cstime,
                        cputime_add(p->stime,
-                       cputime_add(p->signal->stime,
-                                   p->signal->cstime)));
-               p->parent->signal->cmin_flt +=
-                       p->min_flt + p->signal->min_flt + p->signal->cmin_flt;
-               p->parent->signal->cmaj_flt +=
-                       p->maj_flt + p->signal->maj_flt + p->signal->cmaj_flt;
-               p->parent->signal->cnvcsw +=
-                       p->nvcsw + p->signal->nvcsw + p->signal->cnvcsw;
-               p->parent->signal->cnivcsw +=
-                       p->nivcsw + p->signal->nivcsw + p->signal->cnivcsw;
+                       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);
        }
 
@@ -1185,7 +1294,7 @@ static int wait_task_stopped(task_t *p, int delayed_group_leader, int noreap,
 
                exit_code = p->exit_code;
                if (unlikely(!exit_code) ||
-                   unlikely(p->state > TASK_STOPPED))
+                   unlikely(p->state & TASK_TRACED))
                        goto bail_ref;
                return wait_noreap_copyout(p, pid, uid,
                                           why, (exit_code << 8) | 0x7f,
@@ -1232,7 +1341,7 @@ bail_ref:
 
        /* move to end of parent's list to avoid starvation */
        remove_parent(p);
-       add_parent(p, p->parent);
+       add_parent(p);
 
        write_unlock_irq(&tasklist_lock);
 
@@ -1361,6 +1470,15 @@ repeat:
 
                        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*/