Add ability to exclude mutex from tests

We need to be able to exclude mbedtls_test_info_mutex() from the normal
tests, as this mutex has to be locked to report mutex errors, and also
reports as leaked, due to where it is initialised / free'd.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>

tests/src/threading_helpers.c

@@ -117,10 +117,28 @@ static void mbedtls_test_mutex_usage_error(mbedtls_threading_mutex_t *mutex,
      * mbedtls_test_mutex_usage_check() will mark it as failed. */
 }
 
+extern mbedtls_threading_mutex_t mbedtls_test_info_mutex;
+
+static int mbedtls_test_mutex_can_test(mbedtls_threading_mutex_t *mutex)
+{
+    /* If we attempt to run tests on this mutex then we are going to run into a
+     * couple of problems:
+     * 1. If any test on this mutex fails, we are going to deadlock when
+     * reporting that failure, as we already hold the mutex at that point.
+     * 2. Given the 'global' position of the initialization and free of this
+     * mutex, it will be shown as leaked on the first test run. */
+    if (mutex == &mbedtls_test_info_mutex) {
+        return 0;
+    }
+
+    return 1;
+}
+
 static void mbedtls_test_wrap_mutex_init(mbedtls_threading_mutex_t *mutex)
 {
     mutex_functions.init(mutex);
 
+    if (mbedtls_test_mutex_can_test(mutex)) {
         if (mutex_functions.lock(&mbedtls_test_mutex_mutex) == 0) {
             mutex->state = MUTEX_IDLE;
             ++live_mutexes;
@@ -128,9 +146,11 @@ static void mbedtls_test_wrap_mutex_init(mbedtls_threading_mutex_t *mutex)
             mutex_functions.unlock(&mbedtls_test_mutex_mutex);
         }
     }
+}
 
 static void mbedtls_test_wrap_mutex_free(mbedtls_threading_mutex_t *mutex)
 {
+    if (mbedtls_test_mutex_can_test(mutex)) {
         if (mutex_functions.lock(&mbedtls_test_mutex_mutex) == 0) {
 
             switch (mutex->state) {
@@ -151,6 +171,8 @@ static void mbedtls_test_wrap_mutex_free(mbedtls_threading_mutex_t *mutex)
 
             mutex_functions.unlock(&mbedtls_test_mutex_mutex);
         }
+    }
+
     mutex_functions.free(mutex);
 }
 
@@ -160,6 +182,8 @@ static int mbedtls_test_wrap_mutex_lock(mbedtls_threading_mutex_t *mutex)
      * is to hold the passed in and internal mutex - otherwise we create a race
      * condition. */
     int ret = mutex_functions.lock(mutex);
+
+    if (mbedtls_test_mutex_can_test(mutex)) {
         if (mutex_functions.lock(&mbedtls_test_mutex_mutex) == 0) {
             switch (mutex->state) {
                 case MUTEX_FREED:
@@ -180,6 +204,8 @@ static int mbedtls_test_wrap_mutex_lock(mbedtls_threading_mutex_t *mutex)
 
             mutex_functions.unlock(&mbedtls_test_mutex_mutex);
         }
+    }
+
     return ret;
 }
 
@@ -188,6 +214,7 @@ static int mbedtls_test_wrap_mutex_unlock(mbedtls_threading_mutex_t *mutex)
     /* Lock the internal mutex first and change state, so that the only way to
      * change the state is to hold the passed in and internal mutex - otherwise
      * we create a race condition. */
+    if (mbedtls_test_mutex_can_test(mutex)) {
         if (mutex_functions.lock(&mbedtls_test_mutex_mutex) == 0) {
             switch (mutex->state) {
                 case MUTEX_FREED:
@@ -205,6 +232,8 @@ static int mbedtls_test_wrap_mutex_unlock(mbedtls_threading_mutex_t *mutex)
             }
             mutex_functions.unlock(&mbedtls_test_mutex_mutex);
         }
+    }
+
     return mutex_functions.unlock(mutex);
 }