commit 3eedfda1fed73f15d7737c77fec9fe60a9b38fa2
Author: Josh Stone <jistone@redhat.com>
Date:   Wed Jan 27 14:20:06 2016 -0800

    PR19525: always use a SIGUSR2 handler in stapio
    
    It was conditionally ignored by commit 62d2a73ee995, to avoid confusing
    error messages about file rotation when there's no output file.
    
    But bulk-mode close_relayfs() still needs the signal to cause EINTR on
    the waiting threads, so SIG_IGN is too much.  Now we just return from
    the handler immediately if there's no output file to rotate.
    
    Also add a SIGUSR2 test for the original error and with bulk mode.

diff --git a/staprun/relay.c b/staprun/relay.c
index e994cdec9f6d..010063dda687 100644
--- a/staprun/relay.c
+++ b/staprun/relay.c
@@ -212,7 +212,7 @@ error_out:
 static void switchfile_handler(int sig)
 {
 	int i;
-	if (stop_threads)
+	if (stop_threads || !outfile_name)
 		return;
 	for (i = 0; i < ncpus; i++)
 		if (reader[i] && switch_file[i]) {
@@ -355,7 +355,7 @@ int init_relayfs(void)
 	}
 
         memset(&sa, 0, sizeof(sa));
-        sa.sa_handler = outfile_name ? switchfile_handler : SIG_IGN;
+        sa.sa_handler = switchfile_handler;
         sa.sa_flags = 0;
         sigemptyset(&sa.sa_mask);
         sigaction(SIGUSR2, &sa, NULL);
diff --git a/testsuite/systemtap.base/sigusr2.exp b/testsuite/systemtap.base/sigusr2.exp
new file mode 100644
index 000000000000..76ec28a54f22
--- /dev/null
+++ b/testsuite/systemtap.base/sigusr2.exp
@@ -0,0 +1,18 @@
+# Check that SIGUSR2 doesn't cause errors when not using file rotation.
+#
+# It used to say something like:
+#   stapio:open_outfile:75: ERROR: -S is set without -o. Please file a bug report.
+#   ERROR: Couldn't open file for cpu 0, exiting.: Success
+
+
+set test "sigusr2"
+stap_run $srcdir/$subdir/$test.stp no_load $all_pass_string -g
+
+# PR19525: In bulk-mode (-b), close_relayfs() expects SIGUSR2 to cause EINTR on
+# the relay threads, so it can't be SIG_IGN.  But the output is written to
+# files for later stap-merge, so we can't use normal proc stap_run.
+# Just make sure it doesn't hang, at least.
+
+set result_string {}
+stap_run3 "$test bulk" $srcdir/$subdir/$test.stp -g -b -c true
+
diff --git a/testsuite/systemtap.base/sigusr2.stp b/testsuite/systemtap.base/sigusr2.stp
new file mode 100644
index 000000000000..dd2cc485e4b6
--- /dev/null
+++ b/testsuite/systemtap.base/sigusr2.stp
@@ -0,0 +1,18 @@
+/*
+ * sigusr2.stp
+ *
+ * Check that SIGUSR2 doesn't cause errors when not using file rotation.
+ */
+
+probe begin
+{
+	println("systemtap starting probe")
+	raise(%{ SIGUSR2 %})
+}
+
+probe end
+{
+	println("systemtap ending probe")
+	println("systemtap test success")
+}
+