[PATCH AUTOSEL 6.6 25/59] selftests: tracing: Use mutex_unlock for testing glob filter

[Sasha Levin <sashal@kernel.org>]

From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>

[ Upstream commit a089bb2822a49b0c5777a8936f82c1f8629231fb ]

Since commit c5b6ababd21a ("locking/mutex: implement
mutex_trylock_nested") makes mutex_trylock() as an inlined
function if CONFIG_DEBUG_LOCK_ALLOC=y, we can not use
mutex_trylock() for testing the glob filter of ftrace.

Use mutex_unlock instead.

Link: https://lore.kernel.org/r/175151680309.2149615.9795104805153538717.stgit@mhiramat.tok.corp.google.com
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

## Backport Status: YES

This commit should be backported to stable kernel trees for the
following reasons:

1. **It fixes a test regression**: The commit c5b6ababd21a changed
   mutex_trylock() from being a regular function to an inline macro when
   CONFIG_DEBUG_LOCK_ALLOC=y. This broke the ftrace glob filter selftest
   that was trying to match functions with the pattern `mutex*try*`.
   Since mutex_trylock is no longer a regular function symbol in certain
   configurations, the test would fail.

2. **Simple and contained fix**: The change is minimal - it simply
   replaces the test pattern from `mutex*try*` to `mutex*unl*` on line
   32. This is a one-line change that:
   - Changes the glob pattern from matching mutex_trylock functions to
     mutex_unlock functions
   - Maintains the same test logic and purpose (testing glob pattern
     matching)
   - mutex_unlock remains a regular function symbol regardless of
     CONFIG_DEBUG_LOCK_ALLOC

3. **No functional changes to kernel code**: This only affects a
   selftest, not any kernel functionality. The risk of regression is
   zero for normal kernel operation.

4. **Test reliability**: Without this fix, the ftrace selftest suite
   would fail on kernels built with CONFIG_DEBUG_LOCK_ALLOC=y after
   commit c5b6ababd21a is applied. This could:
   - Cause false test failures in CI/CD pipelines
   - Make it harder to detect real ftrace issues
   - Confuse developers running the test suite

5. **Clear dependency**: The commit message explicitly states this is
   needed "Since commit c5b6ababd21a" which indicates this is a direct
   fix for a known regression introduced by that specific commit.

The change is exactly the type that stable rules recommend: it fixes a
clear bug (test regression), is minimal in scope, has no risk of
breaking functionality, and maintains test coverage for an important
kernel feature (ftrace glob filtering).

 .../testing/selftests/ftrace/test.d/ftrace/func-filter-glob.tc  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func-filter-glob.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func-filter-glob.tc
index 4b994b6df5ac..ed81eaf2afd6 100644
--- a/tools/testing/selftests/ftrace/test.d/ftrace/func-filter-glob.tc
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/func-filter-glob.tc
@@ -29,7 +29,7 @@ ftrace_filter_check 'schedule*' '^schedule.*$'
 ftrace_filter_check '*pin*lock' '.*pin.*lock$'
 
 # filter by start*mid*
-ftrace_filter_check 'mutex*try*' '^mutex.*try.*'
+ftrace_filter_check 'mutex*unl*' '^mutex.*unl.*'
 
 # Advanced full-glob matching feature is recently supported.
 # Skip the tests if we are sure the kernel does not support it.
-- 
2.39.5