perf test: Make test_arm_callgraph_fp.sh more robust

The 2 second sleep can cause the test to fail on very slow network file
systems because Perf ends up being killed before it finishes starting
up.

Fix it by making the leafloop workload end after a fixed time like the
other workloads so there is no need to kill it after 2 seconds.

Also remove the 1 second start sampling delay because it is similarly
fragile. Instead, search through all samples for a matching one, rather
than just checking the first sample and hoping it's in the right place.

Fixes: cd6382d8 ("perf test arm64: Test unwinding using fame-pointer (fp) mode")
Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: German Gomez <german.gomez@arm.com>
Cc: Spoorthy S <spoorts2@in.ibm.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240612140316.3006660-1-james.clark@arm.com

tools/perf/tests/shell/test_arm_callgraph_fp.sh

@@ -28,28 +28,21 @@ cleanup_files()
 
 trap cleanup_files EXIT TERM INT
 
-# Add a 1 second delay to skip samples that are not in the leaf() function
 # shellcheck disable=SC2086
-perf record -o "$PERF_DATA" --call-graph fp -e cycles//u -D 1000 --user-callchains -- $TEST_PROGRAM 2> /dev/null &
-PID=$!
+perf record -o "$PERF_DATA" --call-graph fp -e cycles//u --user-callchains -- $TEST_PROGRAM
 
-echo " + Recording (PID=$PID)..."
-sleep 2
-echo " + Stopping perf-record..."
-
-kill $PID
-wait $PID
+# Try opening the file so any immediate errors are visible in the log
+perf script -i "$PERF_DATA" -F comm,ip,sym | head -n4
 
-# expected perf-script output:
+# expected perf-script output if 'leaf' has been inserted correctly:
 #
-# program
+# perf
 # 	728 leaf
 # 	753 parent
 # 	76c leafloop
-# ...
+# ... remaining stack to main() ...
 
-perf script -i "$PERF_DATA" -F comm,ip,sym | head -n4
-perf script -i "$PERF_DATA" -F comm,ip,sym | head -n4 | \
-	awk '{ if ($2 != "") sym[i++] = $2 } END { if (sym[0] != "leaf" ||
-						       sym[1] != "parent" ||
-						       sym[2] != "leafloop") exit 1 }'
+# Each frame is separated by a tab, some spaces and an address
+SEP="[[:space:]]+ [[:xdigit:]]+"
+perf script -i "$PERF_DATA" -F comm,ip,sym | tr '\n' ' ' | \
+	grep -E -q "perf $SEP leaf $SEP parent $SEP leafloop"

tools/perf/tests/workloads/leafloop.c

 /* SPDX-License-Identifier: GPL-2.0 */
+#include <signal.h>
 #include <stdlib.h>
 #include <linux/compiler.h>
+#include <unistd.h>
 #include "../tests.h"
 
 /* We want to check these symbols in perf script */
@@ -8,10 +10,16 @@ noinline void leaf(volatile int b);
 noinline void parent(volatile int b);
 
 static volatile int a;
+static volatile sig_atomic_t done;
+
+static void sighandler(int sig __maybe_unused)
+{
+	done = 1;
+}
 
 noinline void leaf(volatile int b)
 {
-	for (;;)
+	while (!done)
 		a += b;
 }
 
@@ -22,12 +30,16 @@ noinline void parent(volatile int b)
 
 static int leafloop(int argc, const char **argv)
 {
-	int c = 1;
+	int sec = 1;
 
 	if (argc > 0)
-		c = atoi(argv[0]);
+		sec = atoi(argv[0]);
+
+	signal(SIGINT, sighandler);
+	signal(SIGALRM, sighandler);
+	alarm(sec);
 
-	parent(c);
+	parent(sec);
 	return 0;
 }