linux-kernel - [PATCH v3] selftests/ftrace: Do not trace do_softirq because of PREEMPT

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Date:   Mon, 14 Feb 2022 09:36:57 +0100
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,
        linux-rt-users@...r.kernel.org, joseph.salisbury@...onical.com
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: [PATCH v3] selftests/ftrace: Do not trace do_softirq because of PREEMPT_RT

The PREEMPT_RT patchset does not use do_softirq() function thus trying
to filter for do_softirq fails for such kernel:

  echo do_softirq
  ftracetest: 81: echo: echo: I/O error

Choose some other visible function for the test.  The function does not
have to be actually executed during the test, because it is only testing
filter API interface.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

---

Changes since v2:
1. Rephrase commit msg, after comments from Sebastian.
2. Add review tag.

Changes since v1:
1. Use scheduler_tick.
2. Add review tag.

Notes:
I understand that the failure does not exist on mainline kernel (only
with PREEMPT_RT patchset) but the change does not harm it.

If it is not suitable alone, please consider it for RT patchset.
---
 .../selftests/ftrace/test.d/ftrace/func_set_ftrace_file.tc      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func_set_ftrace_file.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func_set_ftrace_file.tc
index e96e279e0533..25432b8cd5bd 100644
--- a/tools/testing/selftests/ftrace/test.d/ftrace/func_set_ftrace_file.tc
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_set_ftrace_file.tc
@@ -19,7 +19,7 @@ fail() { # mesg
 
 FILTER=set_ftrace_filter
 FUNC1="schedule"
-FUNC2="do_softirq"
+FUNC2="scheduler_tick"
 
 ALL_FUNCS="#### all functions enabled ####"
 
-- 
2.32.0