[PATCH 3/8] perf mutex: Add DEFINE_MUTEX() static initializer

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

For file scope mutexes, so that they don't need a constructor function
to initialize them at startup, mirroring PTHREAD_MUTEX_INITIALIZER
while keeping the clang -Wthread-safety annotations of struct mutex.

DEBUG=1 builds have mutex_init() set PTHREAD_MUTEX_ERRORCHECK, making
the CHECK_ERR() paths in mutex_lock()/mutex_unlock() report relocking a
held mutex and unlocking one that isn't held.  PTHREAD_MUTEX_INITIALIZER
gives a default type mutex, so statically initialized ones would silently
lose that: use PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, a glibc
extension, falling back to the default type in libcs that lack it.

Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/mutex.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
index 70232d8d094f8bfc..fe04db21d19c5b0b 100644
--- a/tools/perf/util/mutex.h
+++ b/tools/perf/util/mutex.h
@@ -92,6 +92,18 @@ struct LOCKABLE mutex {
 	pthread_mutex_t lock;
 };
 
+/*
+ * Statically initialized mutex, for the file scope ones. Error checking
+ * in !NDEBUG builds, like mutex_init(); the glibc-only errorcheck
+ * initializer falls back to the default type elsewhere.
+ */
+#if !defined(NDEBUG) && defined(PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP)
+#define __PERF_MUTEX_INITIALIZER PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
+#else
+#define __PERF_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+#endif
+#define DEFINE_MUTEX(name) struct mutex name = { .lock = __PERF_MUTEX_INITIALIZER }
+
 /* A wrapper around the condition variable implementation. */
 struct cond {
 	pthread_cond_t cond;
-- 
2.55.0