Actually restore pre-P mutex behaviorq10.0-r9rebase

Apps built against versions < P may not actually expect the EBUSY return
code, and may crash or otherwise misbehave. Check for target SDK
versions earlier than P when performing the IsMutexDestroyed check so
any invocation of HandleUsingDestroyedMutex is bypassed and pre-P mutex
behavior is restored.

See 9e989f12d1186231d97dac6d038db7955acebdf3 for the change that
introduced this new behavior.

[aviraxp: Update for P:
s/bionic_get_application_target_sdk_version/android_get_application_target_sdk_version
Remove inline keyword for IsMutexDestroyed()]

Change-Id: I45f8882c9527c63eed1ef5820a5004b8958d58ea

1 files changed, 9 insertions, 4 deletions

diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
index 6f1cf1367..478b31f8e 100644
--- a/libc/bionic/pthread_mutex.cpp
+++ b/libc/bionic/pthread_mutex.cpp
@@ -784,16 +784,21 @@ static int MutexLockWithTimeout(pthread_mutex_internal_t* mutex, bool use_realti
 }  // namespace NonPI
 
 static inline __always_inline bool IsMutexDestroyed(uint16_t mutex_state) {
-    return mutex_state == 0xffff;
+    // Checking for mutex destruction is a P-specific behavior. Bypass the
+    // check if the SDK version precedes P, so that no change in behavior
+    // that may cause crashes is introduced.
+    if (android_get_application_target_sdk_version() >= __ANDROID_API_P__) {
+        return mutex_state == 0xffff;
+    } else {
+        return false;
+    }
 }
 
 // Inlining this function in pthread_mutex_lock() adds the cost of stack frame instructions on
 // ARM64. So make it noinline.
 static int __attribute__((noinline)) HandleUsingDestroyedMutex(pthread_mutex_t* mutex,
                                                                const char* function_name) {
-    if (android_get_application_target_sdk_version() >= __ANDROID_API_P__) {
-        __fortify_fatal("%s called on a destroyed mutex (%p)", function_name, mutex);
-    }
+    __fortify_fatal("%s called on a destroyed mutex (%p)", function_name, mutex);
     return EBUSY;
 }