linux-kernel - [PATCH v2] selftests/ftrace: fix event-no-pid on 1-core machine

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Message-Id: <20210623134315.77472-1-krzysztof.kozlowski@canonical.com>
Date:   Wed, 23 Jun 2021 15:43:15 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] selftests/ftrace: fix event-no-pid on 1-core machine

When running event-no-pid test on small machines (e.g. cloud 1-core
instance), other events might not happen:

    + cat trace
    + cnt=0
    + [ 0 -eq 0 ]
    + fail No other events were recorded
    [15] event tracing - restricts events based on pid notrace filtering [FAIL]

Schedule a simple sleep task to be sure that some other process events
get recorded.

Fixes: ebed9628f5c2 ("selftests/ftrace: Add test to test new set_event_notrace_pid file")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

---

Changes since v1:
1. Correct spelling in commit msg.
2. Add Steven's ack.
---
 .../testing/selftests/ftrace/test.d/event/event-no-pid.tc  | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/selftests/ftrace/test.d/event/event-no-pid.tc b/tools/testing/selftests/ftrace/test.d/event/event-no-pid.tc
index e6eb78f0b954..9933ed24f901 100644
--- a/tools/testing/selftests/ftrace/test.d/event/event-no-pid.tc
+++ b/tools/testing/selftests/ftrace/test.d/event/event-no-pid.tc
@@ -57,6 +57,10 @@ enable_events() {
     echo 1 > tracing_on
 }
 
+other_task() {
+    sleep .001 || usleep 1 || sleep 1
+}
+
 echo 0 > options/event-fork
 
 do_reset
@@ -94,6 +98,9 @@ child=$!
 echo "child = $child"
 wait $child
 
+# Be sure some other events will happen for small systems (e.g. 1 core)
+other_task
+
 echo 0 > tracing_on
 
 cnt=`count_pid $mypid`
-- 
2.27.0