1 files changed, 23 insertions, 5 deletions
diff --git a/tools/testing/selftests/lkdtm/run.sh b/tools/testing/selftests/lkdtm/run.sh
index ee64ff8df8f4..95e904959207 100755
--- a/tools/testing/selftests/lkdtm/run.sh
+++ b/tools/testing/selftests/lkdtm/run.sh
@@ -8,6 +8,7 @@
 #
 set -e
 TRIGGER=/sys/kernel/debug/provoke-crash/DIRECT
+CLEAR_ONCE=/sys/kernel/debug/clear_warn_once
 KSELFTEST_SKIP_TEST=4
 
 # Verify we have LKDTM available in the kernel.
@@ -55,8 +56,14 @@ if echo "$test" | grep -q '^#' ; then
 fi
 
 # If no expected output given, assume an Oops with back trace is success.
+repeat=1
 if [ -z "$expect" ]; then
 	expect="call trace:"
+else
+	if echo "$expect" | grep -q '^repeat:' ; then
+		repeat=$(echo "$expect" | cut -d' ' -f1 | cut -d: -f2)
+		expect=$(echo "$expect" | cut -d' ' -f2-)
+	fi
 fi
 
 # Prepare log for report checking
@@ -67,16 +74,27 @@ cleanup() {
 }
 trap cleanup EXIT
 
+# Reset WARN_ONCE counters so we trip it each time this runs.
+if [ -w $CLEAR_ONCE ] ; then
+	echo 1 > $CLEAR_ONCE
+fi
+
 # Save existing dmesg so we can detect new content below
 dmesg > "$DMESG"
 
-# Most shells yell about signals and we're expecting the "cat" process
-# to usually be killed by the kernel. So we have to run it in a sub-shell
-# and silence errors.
-($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) || true
+# Since the kernel is likely killing the process writing to the trigger
+# file, it must not be the script's shell itself. i.e. we cannot do:
+#     echo "$test" >"$TRIGGER"
+# Instead, use "cat" to take the signal. Since the shell will yell about
+# the signal that killed the subprocess, we must ignore the failure and
+# continue. However we don't silence stderr since there might be other
+# useful details reported there in the case of other unexpected conditions.
+for i in $(seq 1 $repeat); do
+	echo "$test" | cat >"$TRIGGER" || true
+done
 
 # Record and dump the results
-dmesg | diff --changed-group-format='%>' --unchanged-group-format='' "$DMESG" - > "$LOG" || true
+dmesg | comm --nocheck-order -13 "$DMESG" - > "$LOG" || true
 
 cat "$LOG"
 # Check for expected output