From c5516866e80f0d30806a8dc366b616aa3b4ff579 Mon Sep 17 00:00:00 2001
From: David Smith <dsmith@redhat.com>
Date: Thu, 11 Oct 2012 10:55:58 -0500
Subject: [PATCH] Fixed PR14659 so that ptrace can be used on tasks probed with
 systemtap.

* runtime/stp_utrace.c (utrace_set_events): No longer set
  TIF_SYSCALL_TRACE on the target task.
  (utrace_reset): No longer clear TIF_SYSCALL_TRACE on the target task.
* testsuite/systemtap.base/ptrace.exp: New testcase.
---
 runtime/stp_utrace.c                |  8 -----
 testsuite/systemtap.base/ptrace.exp | 46 +++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 8 deletions(-)
 create mode 100644 testsuite/systemtap.base/ptrace.exp

diff --git a/runtime/stp_utrace.c b/runtime/stp_utrace.c
index d14475569..6a0735cdd 100644
--- a/runtime/stp_utrace.c
+++ b/runtime/stp_utrace.c
@@ -809,11 +809,6 @@ int utrace_set_events(struct task_struct *target,
 	engine->flags = events | (engine->flags & ENGINE_STOP);
 	utrace->utrace_flags |= events;
 
-	/* FIXME: Hmm, unsure about calling set_tsk_thread_flag()... */
-	if ((events & UTRACE_EVENT_SYSCALL) &&
-	    !(old_utrace_flags & UTRACE_EVENT_SYSCALL))
-		set_tsk_thread_flag(target, TIF_SYSCALL_TRACE);
-
 	ret = 0;
 	if ((old_flags & ~events) && target != current &&
 	    !task_is_stopped_or_traced(target) && !target->exit_state) {
@@ -953,9 +948,6 @@ static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
 		 */
 		BUG_ON(utrace->death);
 		flags &= UTRACE_EVENT(REAP);
-	} else if (!(flags & UTRACE_EVENT_SYSCALL) &&
-		   test_tsk_thread_flag(task, TIF_SYSCALL_TRACE)) {
-		clear_tsk_thread_flag(task, TIF_SYSCALL_TRACE);
 	}
 
 	if (!flags) {
diff --git a/testsuite/systemtap.base/ptrace.exp b/testsuite/systemtap.base/ptrace.exp
new file mode 100644
index 000000000..358d2646a
--- /dev/null
+++ b/testsuite/systemtap.base/ptrace.exp
@@ -0,0 +1,46 @@
+# Make sure we can use ptrace() on a process probed with systemtap.
+
+set TEST_NAME "ptrace"
+if {![utrace_p]} {
+    untested "$TEST_NAME : no kernel utrace support found"
+    return
+} elseif {![installtest_p]} {
+    untested $TEST_NAME
+    return
+}
+
+# Test process.begin
+set subcmd {strace -e read true}
+set TEST_NAME "ptrace (begin)"
+set script {probe process.begin { next }}
+set cmd {stap -e $script -c $subcmd}
+set output_found 0
+eval spawn $cmd
+expect {
+    -timeout 180
+    -re {^read\(\d+, .+\) = \d+\r\n\+\+\+ exited with 0 \+\+\+\r\n} {
+	set output_found 1
+	exp_continue
+    }
+}
+catch close
+wait
+if { $output_found } { pass "$TEST_NAME" } else { fail "$TEST_NAME" }
+
+# The never probe won't get hit, but including 'print_ubacktrace()' will
+# enable task_finder and vma tracking.
+set TEST_NAME "ptrace (never)"
+set script {probe never{print_ubacktrace()}}
+set cmd {stap -e $script -c $subcmd}
+set output_found 0
+eval spawn $cmd
+expect {
+    -timeout 180
+    -re {^read\(\d+, .+\) = \d+\r\n\+\+\+ exited with 0 \+\+\+\r\n} {
+	set output_found 1
+	exp_continue
+    }
+}
+catch close
+wait
+if { $output_found } { pass "$TEST_NAME" } else { fail "$TEST_NAME" }
-- 
2.43.5