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
diff --git a/tests/stdio_ext_test.cpp b/tests/stdio_ext_test.cpp
index c95cbbd..7872567 100644
--- a/tests/stdio_ext_test.cpp
+++ b/tests/stdio_ext_test.cpp
@@ -30,6 +30,7 @@
#include <locale.h>
#include "TemporaryFile.h"
+#include "utils.h"
TEST(stdio_ext, __fbufsize) {
FILE* fp = fopen("/proc/version", "r");
@@ -140,3 +141,24 @@
ASSERT_EQ(FSETLOCKING_INTERNAL, __fsetlocking(fp, FSETLOCKING_QUERY));
fclose(fp);
}
+
+static void LockingByCallerHelper(std::atomic<pid_t>* pid) {
+ *pid = gettid();
+ flockfile(stdout);
+ funlockfile(stdout);
+}
+
+TEST(stdio_ext, __fsetlocking_BYCALLER) {
+ // Check if users can use flockfile/funlockfile to protect stdio operations.
+ int old_state = __fsetlocking(stdout, FSETLOCKING_BYCALLER);
+ flockfile(stdout);
+ pthread_t thread;
+ std::atomic<pid_t> pid(0);
+ ASSERT_EQ(0, pthread_create(&thread, nullptr,
+ reinterpret_cast<void* (*)(void*)>(LockingByCallerHelper), &pid));
+ WaitUntilThreadSleep(pid);
+ funlockfile(stdout);
+
+ ASSERT_EQ(0, pthread_join(thread, nullptr));
+ __fsetlocking(stdout, old_state);
+}