[PATCH 6.6 116/301] selftests/ftrace: Fix event filter target_func selection

Greg Kroah-Hartman
2024-05-14T11:09:39Z

From: Mark Rutland <mark.rutland@arm.com>

[ Upstream commit 8ecab2e64572f1aecdfc5a8feae748abda6e3347 ]

The event filter function test has been failing in our internal test
farm:

| # not ok 33 event filter function - test event filtering on functions

Running the test in verbose mode indicates that this is because the test
erroneously determines that kmem_cache_free() is the most common caller
of kmem_cache_free():

# # + cut -d: -f3 trace
# # + sed s/call_site=([^+]*)+0x.*/1/
# # + sort
# # + uniq -c
# # + sort
# # + tail -n 1
# # + sed s/^[ 0-9]*//
# # + target_func=kmem_cache_free

... and as kmem_cache_free() doesn't call itself, setting this as the
filter function for kmem_cache_free() results in no hits, and
consequently the test fails:

# # + grep kmem_cache_free trace
# # + grep kmem_cache_free
# # + wc -l
# # + hitcnt=0
# # + grep kmem_cache_free trace
# # + grep -v kmem_cache_free
# # + wc -l
# # + misscnt=0
# # + [ 0 -eq 0 ]
# # + exit_fail

This seems to be because the system in question has tasks with ':' in
their name (which a number of kernel worker threads have). These show up
in the trace, e.g.

test:.sh-1299 [004] ..... 2886.040608: kmem_cache_free: call_site=putname+0xa4/0xc8 ptr=000000000f4d22f4 name=names_cache

... and so when we try to extact the call_site with:

cut -d: -f3 trace | sed 's/call_site=\([^+]*\)+0x.*/\1/'

... the 'cut' command will extrace the column containing
'kmem_cache_free' rather than the column containing 'call_site=...', and
the 'sed' command will leave this unchanged. Consequently, the test will
decide to use 'kmem_cache_free' as the filter function, resulting in the
failure seen above.

Fix this by matching the 'call_site=<func>' part specifically to extract
the function name.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Aishwarya TCV <aishwarya.tcv@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: linux-trace-kernel@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../selftests/ftrace/test.d/filter/event-filter-function.tc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/filter/event-filter-function.tc b/tools/testing/selftests/ftrace/test.d/filter/event-filter-function.tc
index 2de7c61d1ae30..3f74c09c56b62 100644
--- a/tools/testing/selftests/ftrace/test.d/filter/event-filter-function.tc
+++ b/tools/testing/selftests/ftrace/test.d/filter/event-filter-function.tc
@@ -24,7 +24,7 @@ echo 0 > events/enable
echo "Get the most frequently calling function"
sample_events

-target_func=`cut -d: -f3 trace | sed 's/call_site=\([^+]*\)+0x.*/\1/' | sort | uniq -c | sort | tail -n 1 | sed 's/^[ 0-9]*//'`
+target_func=`cat trace | grep -o 'call_site=\([^+]*\)' | sed 's/call_site=//' | sort | uniq -c | sort | tail -n 1 | sed 's/^[ 0-9]*//'`
if [ -z "$target_func" ]; then
exit_fail
fi
--
2.43.0