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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 550/593] selftests/ftrace: fix event-no-pid on 1-core machine
Date:   Mon, 12 Jul 2021 08:11:50 +0200
Message-Id: <20210712060954.808789890@linuxfoundation.org>
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From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

[ Upstream commit 07b60713b57a8f952d029a2b6849d003d9c16108 ]

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@canonical.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../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`
-- 
2.30.2