[PATCH 6/7] hw_breakpoint_test: fix test_many_cpus failure on large systems

[Jia He]

On systems with many CPUs (e.g. 128 cores x 4 HW breakpoint slots =
512 = MAX_TEST_BREAKPOINTS), test_many_cpus() advances idx to
MAX_TEST_BREAKPOINTS after the last fill_bp_slots(). The subsequent
register_test_bp() call hits WARN_ON(idx >= MAX_TEST_BREAKPOINTS),
returns NULL, and the -ENOSPC expectation fails.

Bail out of the loop when idx reaches the limit. Earlier iterations
already validate the NOSPC path on other CPUs.

To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
To: Ingo Molnar <mingo@xxxxxxxxxx>
To: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
To: Namhyung Kim <namhyung@xxxxxxxxxx>
To: Mark Rutland <mark.rutland@xxxxxxx>
To: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
To: Jiri Olsa <jolsa@xxxxxxxxxx>
To: Ian Rogers <irogers@xxxxxxxxxx>
To: Adrian Hunter <adrian.hunter@xxxxxxxxx>
To: James Clark <james.clark@xxxxxxxxxx>
Cc: linux-perf-users@xxxxxxxxxxxxxxx

Signed-off-by: Jia He <justin.he@xxxxxxx>
---
 kernel/events/hw_breakpoint_test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/events/hw_breakpoint_test.c b/kernel/events/hw_breakpoint_test.c
index 2cfeeecf8de9..943d040d2224 100644
--- a/kernel/events/hw_breakpoint_test.c
+++ b/kernel/events/hw_breakpoint_test.c
@@ -137,6 +137,9 @@ static void test_many_cpus(struct kunit *test)
 	for_each_online_cpu(cpu) {
 		bool do_continue = fill_bp_slots(test, &idx, cpu, NULL, 0);
 
+		if (idx >= MAX_TEST_BREAKPOINTS)
+			break;
+
 		TEST_EXPECT_NOSPC(register_test_bp(cpu, NULL, idx));
 		if (!do_continue)
 			break;
-- 
2.34.1