Change _stdio_handles_locking into _caller_handles_locking.

It is reported by tsan that funlockfile() can unlock an unlocked mutex.
It happens when printf() is called before fopen() or other stdio stuff.
As FLOCKFILE(fp) is called before __sinit(), _stdio_handles_locking is false,
and _FLOCK(fp) will not be locked. But then cantwrite(fp) in __vfprintf()
calls__sinit(), which makes _stdio_handles_locking become true, and
FUNLOCKFILE(fp) unlocks _FLOCK(fp).

Change _stdio_handles_locking into _caller_handles_locking,
so __sinit() won't change its value. Add test due to my previous fault.

Bug: 25392375
Change-Id: I483e3c3cdb28da65e62f1fd9615bf58c5403b4dd

tests/pthread_test.cpp

@@ -30,12 +30,8 @@
 #include <unwind.h>
 
 #include <atomic>
-#include <regex>
 #include <vector>
 
-#include <base/file.h>
-#include <base/stringprintf.h>
-
 #include "private/bionic_macros.h"
 #include "private/ScopeGuard.h"
 #include "BionicDeathTest.h"
@@ -43,8 +39,6 @@
 
 #include "utils.h"
 
-extern "C" pid_t gettid();
-
 TEST(pthread, pthread_key_create) {
   pthread_key_t key;
   ASSERT_EQ(0, pthread_key_create(&key, NULL));
@@ -721,23 +715,6 @@ TEST(pthread, pthread_rwlock_smoke) {
   ASSERT_EQ(0, pthread_rwlock_destroy(&l));
 }
 
-static void WaitUntilThreadSleep(std::atomic<pid_t>& tid) {
-  while (tid == 0) {
-    usleep(1000);
-  }
-  std::string filename = android::base::StringPrintf("/proc/%d/stat", tid.load());
-  std::regex regex {R"(\s+S\s+)"};
-
-  while (true) {
-    std::string content;
-    ASSERT_TRUE(android::base::ReadFileToString(filename, &content));
-    if (std::regex_search(content, regex)) {
-      break;
-    }
-    usleep(1000);
-  }
-}
-
 struct RwlockWakeupHelperArg {
   pthread_rwlock_t lock;
   enum Progress {