[PATCH v3 15/18] perf mutex: Add thread safety annotations

Ian Rogers
2022-08-24T15:41:49Z

Add thread safety annotations to struct mutex so that when compiled with
clang's -Wthread-safety warnings are generated for erroneous lock
patterns. NO_THREAD_SAFETY_ANALYSIS is needed for
mutex_lock/mutex_unlock as the analysis doesn't under pthread calls.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/mutex.c | 2 ++
tools/perf/util/mutex.h | 72 ++++++++++++++++++++++++++++++++++++++---
2 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/mutex.c b/tools/perf/util/mutex.c
index 892294ac1769..ec813093276d 100644
--- a/tools/perf/util/mutex.c
+++ b/tools/perf/util/mutex.c
@@ -50,11 +50,13 @@ void mutex_destroy(struct mutex *mtx)
}

void mutex_lock(struct mutex *mtx)
+ NO_THREAD_SAFETY_ANALYSIS
{
CHECK_ERR(pthread_mutex_lock(&mtx->lock));
}

void mutex_unlock(struct mutex *mtx)
+ NO_THREAD_SAFETY_ANALYSIS
{
CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
}
diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
index c9e110a2b55e..48a2d87598f0 100644
--- a/tools/perf/util/mutex.h
+++ b/tools/perf/util/mutex.h
@@ -5,11 +5,73 @@
#include <pthread.h>
#include <stdbool.h>

+/*
+ * A function-like feature checking macro that is a wrapper around
+ * `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
+ * nonzero constant integer if the attribute is supported or 0 if not.
+ */
+#ifdef __has_attribute
+#define HAVE_ATTRIBUTE(x) __has_attribute(x)
+#else
+#define HAVE_ATTRIBUTE(x) 0
+#endif
+
+
+#if HAVE_ATTRIBUTE(guarded_by) && HAVE_ATTRIBUTE(pt_guarded_by) && \
+ HAVE_ATTRIBUTE(lockable) && HAVE_ATTRIBUTE(exclusive_lock_function) && \
+ HAVE_ATTRIBUTE(exclusive_trylock_function) && HAVE_ATTRIBUTE(exclusive_locks_required) && \
+ HAVE_ATTRIBUTE(no_thread_safety_analysis)
+
+/* Documents if a shared field or global variable needs to be protected by a mutex. */
+#define GUARDED_BY(x) __attribute__((guarded_by(x)))
+
+/*
+ * Documents if the memory location pointed to by a pointer should be guarded by
+ * a mutex when dereferencing the pointer.
+ */
+#define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
+
+/* Documents if a type is a lockable type. */
+#define LOCKABLE __attribute__((capability("lockable")))
+
+/* Documents functions that acquire a lock in the body of a function, and do not release it. */
+#define EXCLUSIVE_LOCK_FUNCTION(...) __attribute__((exclusive_lock_function(__VA_ARGS__)))
+
+/*
+ * Documents functions that expect a lock to be held on entry to the function,
+ * and release it in the body of the function.
+ */
+#define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
+
+/* Documents functions that try to acquire a lock, and return success or failure. */
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
+ __attribute__((exclusive_trylock_function(__VA_ARGS__)))
+
+
+/* Documents a function that expects a mutex to be held prior to entry. */
+#define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
+
+/* Turns off thread safety checking within the body of a particular function. */
+#define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
+
+#else
+
+#define GUARDED_BY(x)
+#define PT_GUARDED_BY(x)
+#define LOCKABLE
+#define EXCLUSIVE_LOCK_FUNCTION(...)
+#define UNLOCK_FUNCTION(...)
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...)
+#define EXCLUSIVE_LOCKS_REQUIRED(...)
+#define NO_THREAD_SAFETY_ANALYSIS
+
+#endif
+
/*
* A wrapper around the mutex implementation that allows perf to error check
* usage, etc.
*/
-struct mutex {
+struct LOCKABLE mutex {
pthread_mutex_t lock;
};

@@ -27,9 +89,9 @@ void mutex_init(struct mutex *mtx);
void mutex_init_pshared(struct mutex *mtx);
void mutex_destroy(struct mutex *mtx);

-void mutex_lock(struct mutex *mtx);
-void mutex_unlock(struct mutex *mtx);
-bool mutex_trylock(struct mutex *mtx);
+void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);
+void mutex_unlock(struct mutex *mtx) UNLOCK_FUNCTION(*mtx);
+bool mutex_trylock(struct mutex *mtx) EXCLUSIVE_TRYLOCK_FUNCTION(true, *mtx);

/* Default initialize the cond struct. */
void cond_init(struct cond *cnd);
@@ -40,7 +102,7 @@ void cond_init(struct cond *cnd);
void cond_init_pshared(struct cond *cnd);
void cond_destroy(struct cond *cnd);

-void cond_wait(struct cond *cnd, struct mutex *mtx);
+void cond_wait(struct cond *cnd, struct mutex *mtx) EXCLUSIVE_LOCKS_REQUIRED(mtx);
void cond_signal(struct cond *cnd);
void cond_broadcast(struct cond *cnd);

--
2.37.2.609.g9ff673ca1a-goog