a.patch

commit 01df5daee0ec4c2d4b0714095bfed1d475846f7e
Author: Yichun Zhang (agentzh) <agentzh@gmail.com>
Date:   Wed Oct 28 22:28:41 2020 -0700

    fixed Dl hang.

diff --git a/runtime/linux/task_finder2.c b/runtime/linux/task_finder2.c
index 0ba614741..8aa0ed71a 100644
--- a/runtime/linux/task_finder2.c
+++ b/runtime/linux/task_finder2.c
@@ -876,7 +876,7 @@ __stp_utrace_attach_match_filename(struct task_struct *tsk,
                // when the thread gets quiesced.
                rc = __stp_utrace_attach(tsk, &tgt->ops, tgt,
                                         __STP_ATTACHED_TASK_EVENTS,
-                                        UTRACE_STOP);
+                                        UTRACE_INTERRUPT);
                if (rc != 0 && rc != EPERM)
                        break;
                tgt->engine_attached = 1;
@@ -1778,7 +1778,7 @@ stap_start_task_finder(void)
                        // Set up events we need for attached tasks.
                        rc = __stp_utrace_attach(tsk, &tgt->ops, tgt,
                                                 __STP_ATTACHED_TASK_EVENTS,
-                                                UTRACE_STOP);
+                                                UTRACE_INTERRUPT);

                        dbug_task(2, "__stp_utrace_attach() for %d returned %d", tsk->tgid,
                                  rc);