Merge "Fix potential race condition on CTS TC pthread_gettid_np" into marshmallow-cts-dev

Root cause:
If start_routine thread exits before pthread_gettid_np is invokded, the "tid" field
will be cleared so that pthread_gettid_np will get "0" (which is cleared by kernel, 
due to the flag "CLONE_CHILD_CLEARTID" is set while calling clone system call inside
pthread_create).

Proposed patch:
Use a mutex to guarantee pthread_gettid_np will be invoked and returned before the
start_routine exits

Signed-off-by: Junjie Hu <junjie.hu@mediatek.com>

Change-Id: I22411f1b0f7446d76a0373cef4ccec858fac7018

libc/bionic/pthread_internal.h

@@ -130,13 +130,8 @@ __LIBC_HIDDEN__ void pthread_key_clean_all(void);
  */
 #define PTHREAD_STACK_SIZE_DEFAULT ((1 * 1024 * 1024) - SIGSTKSZ)
 
-// Leave room for a guard page in the internally created signal stacks.
-#if defined(__LP64__)
-// SIGSTKSZ is not big enough for 64-bit arch. See http://b/23041777.
-#define SIGNAL_STACK_SIZE (16 * 1024 + PAGE_SIZE)
-#else
+/* Leave room for a guard page in the internally created signal stacks. */
 #define SIGNAL_STACK_SIZE (SIGSTKSZ + PAGE_SIZE)
-#endif
 
 /* Needed by fork. */
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_prepare();

tests/pthread_test.cpp

@@ -27,7 +27,6 @@
 #include <sys/syscall.h>
 #include <time.h>
 #include <unistd.h>
-#include <unwind.h>
 
 #include <atomic>
 #include <regex>
@@ -1245,8 +1244,11 @@ TEST(pthread, pthread_attr_getstack_18908062) {
 }
 
 #if defined(__BIONIC__)
+static pthread_mutex_t gettid_mutex;
 static void* pthread_gettid_np_helper(void* arg) {
+  pthread_mutex_lock(&gettid_mutex);
   *reinterpret_cast<pid_t*>(arg) = gettid();
+  pthread_mutex_unlock(&gettid_mutex);
   return NULL;
 }
 #endif
@@ -1257,11 +1259,15 @@ TEST(pthread, pthread_gettid_np) {
 
   pid_t t_gettid_result;
   pthread_t t;
+  pthread_mutex_init(&gettid_mutex, NULL);
+  pthread_mutex_lock(&gettid_mutex);
   pthread_create(&t, NULL, pthread_gettid_np_helper, &t_gettid_result);
 
   pid_t t_pthread_gettid_np_result = pthread_gettid_np(t);
+  pthread_mutex_unlock(&gettid_mutex);
 
   pthread_join(t, NULL);
+  pthread_mutex_destroy(&gettid_mutex);
 
   ASSERT_EQ(t_gettid_result, t_pthread_gettid_np_result);
 #else
@@ -1572,26 +1578,3 @@ TEST_F(pthread_DeathTest, pthread_mutex_unlock_null_64) {
   GTEST_LOG_(INFO) << "This test tests bionic implementation details on 64 bit devices.";
 #endif
 }
-
-extern _Unwind_Reason_Code FrameCounter(_Unwind_Context* ctx, void* arg);
-
-static volatile bool signal_handler_on_altstack_done;
-
-static void SignalHandlerOnAltStack(int signo, siginfo_t*, void*) {
-  ASSERT_EQ(SIGUSR1, signo);
-  // Check if we have enough stack space for unwinding.
-  int count = 0;
-  _Unwind_Backtrace(FrameCounter, &count);
-  ASSERT_GT(count, 0);
-  // Check if we have enough stack space for logging.
-  std::string s(2048, '*');
-  GTEST_LOG_(INFO) << s;
-  signal_handler_on_altstack_done = true;
-}
-
-TEST(pthread, big_enough_signal_stack_for_64bit_arch) {
-  signal_handler_on_altstack_done = false;
-  ScopedSignalHandler handler(SIGUSR1, SignalHandlerOnAltStack, SA_SIGINFO | SA_ONSTACK);
-  kill(getpid(), SIGUSR1);
-  ASSERT_TRUE(signal_handler_on_altstack_done);
-}

tests/stack_unwinding_test.cpp

@@ -34,7 +34,7 @@
 #define noinline __attribute__((__noinline__))
 #define __unused __attribute__((__unused__))
 
-_Unwind_Reason_Code FrameCounter(_Unwind_Context* ctx __unused, void* arg) {
+static _Unwind_Reason_Code FrameCounter(_Unwind_Context* ctx __unused, void* arg) {
   int* count_ptr = reinterpret_cast<int*>(arg);
 
 #if SHOW_FRAME_LOCATIONS