return NULL;
}
-/*
- * 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.
+/**
+ * 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)
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);
return 0;
}
- if (likely(!ptrace) && unlikely(task_ptrace(p))) {
+ /* dead body doesn't have much to contribute */
+ if (p->exit_state == EXIT_DEAD)
+ 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(task_ptrace(p))) {
+ /* 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);
+
/*
- * This child is hidden by ptrace.
- * We aren't allowed to see it now, but eventually we will.
+ * 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) && task_ptrace(p) &&
+ same_thread_group(p->parent, p->real_parent))
+ 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;
- return 0;
}
- if (p->exit_state == EXIT_DEAD)
- return 0;
-
/*
- * We don't reap group leaders with subthreads.
+ * Wait for stopped. Depending on @ptrace, different stopped state
+ * is used and the two don't interact with each other.
*/
- if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
- return wait_task_zombie(wo, p);
+ ret = wait_task_stopped(wo, ptrace, p);
+ if (ret)
+ return ret;
/*
- * It's stopped or running now, so it might
- * later continue, exit, or stop again.
+ * 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.
*/
- wo->notask_error = 0;
-
- if (task_stopped_code(p, ptrace))
- return wait_task_stopped(wo, ptrace, p);
-
return wait_task_continued(wo, p);
}
git.openpandora.org / pandora-kernel.git / blobdiff