forked from Minki/linux
do_wait reorganization
This breaks out the guts of do_wait into three subfunctions. The control flow is less nonobvious without so much goto. do_wait_thread and ptrace_do_wait contain the main work of the outer loop. wait_consider_task contains the main work of the inner loop. Signed-off-by: Roland McGrath <roland@redhat.com>
This commit is contained in:
Roland McGrath
parent
33af79d12e
commit
98abed0200
215
kernel/exit.c
215
kernel/exit.c
@ -1238,7 +1238,7 @@ static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
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* the lock and this task is uninteresting. If we return nonzero, we have
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* released the lock and the system call should return.
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*/
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static int wait_task_zombie(struct task_struct *p, int noreap,
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static int wait_task_zombie(struct task_struct *p, int options,
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struct siginfo __user *infop,
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int __user *stat_addr, struct rusage __user *ru)
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{
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@ -1246,7 +1246,10 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
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int retval, status, traced;
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pid_t pid = task_pid_vnr(p);
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if (unlikely(noreap)) {
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if (!likely(options & WEXITED))
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return 0;
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if (unlikely(options & WNOWAIT)) {
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uid_t uid = p->uid;
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int exit_code = p->exit_code;
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int why, status;
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@ -1397,13 +1400,16 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
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* released the lock and the system call should return.
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*/
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static int wait_task_stopped(struct task_struct *p,
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int noreap, struct siginfo __user *infop,
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int options, struct siginfo __user *infop,
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int __user *stat_addr, struct rusage __user *ru)
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{
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int retval, exit_code, why;
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uid_t uid = 0; /* unneeded, required by compiler */
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pid_t pid;
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if (!(p->ptrace & PT_PTRACED) && !(options & WUNTRACED))
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return 0;
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exit_code = 0;
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spin_lock_irq(&p->sighand->siglock);
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@ -1421,7 +1427,7 @@ static int wait_task_stopped(struct task_struct *p,
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if (!exit_code)
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goto unlock_sig;
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if (!noreap)
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if (!unlikely(options & WNOWAIT))
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p->exit_code = 0;
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uid = p->uid;
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@ -1442,7 +1448,7 @@ unlock_sig:
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why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
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read_unlock(&tasklist_lock);
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if (unlikely(noreap))
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if (unlikely(options & WNOWAIT))
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return wait_noreap_copyout(p, pid, uid,
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why, exit_code,
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infop, ru);
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@ -1476,7 +1482,7 @@ unlock_sig:
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* the lock and this task is uninteresting. If we return nonzero, we have
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* released the lock and the system call should return.
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*/
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static int wait_task_continued(struct task_struct *p, int noreap,
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static int wait_task_continued(struct task_struct *p, int options,
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struct siginfo __user *infop,
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int __user *stat_addr, struct rusage __user *ru)
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{
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@ -1484,6 +1490,9 @@ static int wait_task_continued(struct task_struct *p, int noreap,
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pid_t pid;
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uid_t uid;
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if (!unlikely(options & WCONTINUED))
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return 0;
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if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
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return 0;
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@ -1493,7 +1502,7 @@ static int wait_task_continued(struct task_struct *p, int noreap,
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spin_unlock_irq(&p->sighand->siglock);
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return 0;
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}
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if (!noreap)
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if (!unlikely(options & WNOWAIT))
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p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
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spin_unlock_irq(&p->sighand->siglock);
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@ -1519,89 +1528,137 @@ static int wait_task_continued(struct task_struct *p, int noreap,
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return retval;
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}
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/*
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* Consider @p for a wait by @parent.
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*
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* -ECHILD should be in *@notask_error before the first call.
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* Returns nonzero for a final return, when we have unlocked tasklist_lock.
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* Returns zero if the search for a child should continue;
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* then *@notask_error is 0 if @p is an eligible child, or still -ECHILD.
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*/
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static int wait_consider_task(struct task_struct *parent,
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struct task_struct *p, int *notask_error,
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enum pid_type type, struct pid *pid, int options,
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struct siginfo __user *infop,
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int __user *stat_addr, struct rusage __user *ru)
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{
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int ret = eligible_child(type, pid, options, p);
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if (ret <= 0)
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return ret;
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if (p->exit_state == EXIT_DEAD)
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return 0;
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/*
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* We don't reap group leaders with subthreads.
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*/
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if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
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return wait_task_zombie(p, options, infop, stat_addr, ru);
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/*
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* It's stopped or running now, so it might
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* later continue, exit, or stop again.
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*/
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*notask_error = 0;
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if (task_is_stopped_or_traced(p))
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return wait_task_stopped(p, options, infop, stat_addr, ru);
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return wait_task_continued(p, options, infop, stat_addr, ru);
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}
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/*
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* Do the work of do_wait() for one thread in the group, @tsk.
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*
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* -ECHILD should be in *@notask_error before the first call.
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* Returns nonzero for a final return, when we have unlocked tasklist_lock.
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* Returns zero if the search for a child should continue; then
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* *@notask_error is 0 if there were any eligible children, or still -ECHILD.
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*/
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static int do_wait_thread(struct task_struct *tsk, int *notask_error,
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enum pid_type type, struct pid *pid, int options,
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struct siginfo __user *infop, int __user *stat_addr,
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struct rusage __user *ru)
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{
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struct task_struct *p;
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list_for_each_entry(p, &tsk->children, sibling) {
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int ret = wait_consider_task(tsk, p, notask_error,
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type, pid, options,
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infop, stat_addr, ru);
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if (ret)
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return ret;
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}
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return 0;
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}
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static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
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enum pid_type type, struct pid *pid, int options,
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struct siginfo __user *infop, int __user *stat_addr,
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struct rusage __user *ru)
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{
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struct task_struct *p;
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/*
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* If we never saw an eligile child, check for children stolen by
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* ptrace. We don't leave -ECHILD in *@notask_error if there are any,
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* because we will eventually be allowed to wait for them again.
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*/
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if (!*notask_error)
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return 0;
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list_for_each_entry(p, &tsk->ptrace_children, ptrace_list) {
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int ret = eligible_child(type, pid, options, p);
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if (unlikely(ret < 0))
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return ret;
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if (ret) {
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*notask_error = 0;
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return 0;
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}
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}
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return 0;
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}
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static long do_wait(enum pid_type type, struct pid *pid, int options,
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struct siginfo __user *infop, int __user *stat_addr,
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struct rusage __user *ru)
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{
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DECLARE_WAITQUEUE(wait, current);
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struct task_struct *tsk;
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int flag, retval;
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int retval;
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add_wait_queue(¤t->signal->wait_chldexit,&wait);
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repeat:
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/* If there is nothing that can match our critier just get out */
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/*
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* If there is nothing that can match our critiera just get out.
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* We will clear @retval to zero if we see any child that might later
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* match our criteria, even if we are not able to reap it yet.
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*/
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retval = -ECHILD;
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if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
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goto end;
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/*
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* We will set this flag if we see any child that might later
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* match our criteria, even if we are not able to reap it yet.
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*/
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flag = retval = 0;
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current->state = TASK_INTERRUPTIBLE;
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read_lock(&tasklist_lock);
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tsk = current;
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do {
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struct task_struct *p;
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list_for_each_entry(p, &tsk->children, sibling) {
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int ret = eligible_child(type, pid, options, p);
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if (!ret)
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continue;
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if (unlikely(ret < 0)) {
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retval = ret;
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} else if (task_is_stopped_or_traced(p)) {
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/*
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* It's stopped now, so it might later
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* continue, exit, or stop again.
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*/
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flag = 1;
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if (!(p->ptrace & PT_PTRACED) &&
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!(options & WUNTRACED))
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continue;
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retval = wait_task_stopped(p,
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(options & WNOWAIT), infop,
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stat_addr, ru);
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} else if (p->exit_state == EXIT_ZOMBIE &&
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!delay_group_leader(p)) {
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/*
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* We don't reap group leaders with subthreads.
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*/
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if (!likely(options & WEXITED))
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continue;
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retval = wait_task_zombie(p,
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(options & WNOWAIT), infop,
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stat_addr, ru);
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} else if (p->exit_state != EXIT_DEAD) {
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/*
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* It's running now, so it might later
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* exit, stop, or stop and then continue.
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*/
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flag = 1;
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if (!unlikely(options & WCONTINUED))
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continue;
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retval = wait_task_continued(p,
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(options & WNOWAIT), infop,
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stat_addr, ru);
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}
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if (retval != 0) /* tasklist_lock released */
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goto end;
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}
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if (!flag) {
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list_for_each_entry(p, &tsk->ptrace_children,
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ptrace_list) {
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flag = eligible_child(type, pid, options, p);
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if (!flag)
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continue;
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if (likely(flag > 0))
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break;
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retval = flag;
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goto end;
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}
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int tsk_result = do_wait_thread(tsk, &retval,
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type, pid, options,
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infop, stat_addr, ru);
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if (!tsk_result)
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tsk_result = ptrace_do_wait(tsk, &retval,
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type, pid, options,
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infop, stat_addr, ru);
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if (tsk_result) {
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/*
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* tasklist_lock is unlocked and we have a final result.
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*/
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retval = tsk_result;
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goto end;
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}
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if (options & __WNOTHREAD)
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break;
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tsk = next_thread(tsk);
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@ -1609,16 +1666,14 @@ repeat:
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} while (tsk != current);
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read_unlock(&tasklist_lock);
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if (flag) {
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if (options & WNOHANG)
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goto end;
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if (!retval && !(options & WNOHANG)) {
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retval = -ERESTARTSYS;
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if (signal_pending(current))
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goto end;
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schedule();
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goto repeat;
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if (!signal_pending(current)) {
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schedule();
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goto repeat;
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}
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}
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retval = -ECHILD;
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end:
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current->state = TASK_RUNNING;
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remove_wait_queue(¤t->signal->wait_chldexit,&wait);
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