8033696: "assert(thread != NULL) failed: just checking" due to...

8033696: "assert(thread != NULL) failed: just checking" due to Thread::current() and JNI pthread interaction
Reviewed-by: dholmes, dsamersoff
Contributed-by: andreas.eriksson@oracle.com

src/os/bsd/vm/os_bsd.cpp

@@ -914,9 +914,20 @@ void os::free_thread(OSThread* osthread) {
 //////////////////////////////////////////////////////////////////////////////
 // thread local storage
 
+// Restore the thread pointer if the destructor is called. This is in case
+// someone from JNI code sets up a destructor with pthread_key_create to run
+// detachCurrentThread on thread death. Unless we restore the thread pointer we
+// will hang or crash. When detachCurrentThread is called the key will be set
+// to null and we will not be called again. If detachCurrentThread is never
+// called we could loop forever depending on the pthread implementation.
+static void restore_thread_pointer(void* p) {
+  Thread* thread = (Thread*) p;
+  os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
+}
+
 int os::allocate_thread_local_storage() {
   pthread_key_t key;
-  int rslt = pthread_key_create(&key, NULL);
+  int rslt = pthread_key_create(&key, restore_thread_pointer);
   assert(rslt == 0, "cannot allocate thread local storage");
   return (int)key;
 }

src/os/linux/vm/os_linux.cpp

@@ -1074,9 +1074,20 @@ void os::free_thread(OSThread* osthread) {
 //////////////////////////////////////////////////////////////////////////////
 // thread local storage
 
+// Restore the thread pointer if the destructor is called. This is in case
+// someone from JNI code sets up a destructor with pthread_key_create to run
+// detachCurrentThread on thread death. Unless we restore the thread pointer we
+// will hang or crash. When detachCurrentThread is called the key will be set
+// to null and we will not be called again. If detachCurrentThread is never
+// called we could loop forever depending on the pthread implementation.
+static void restore_thread_pointer(void* p) {
+  Thread* thread = (Thread*) p;
+  os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
+}
+
 int os::allocate_thread_local_storage() {
   pthread_key_t key;
-  int rslt = pthread_key_create(&key, NULL);
+  int rslt = pthread_key_create(&key, restore_thread_pointer);
   assert(rslt == 0, "cannot allocate thread local storage");
   return (int)key;
 }

src/share/vm/runtime/vmThread.cpp

@@ -316,6 +316,9 @@ void VMThread::run() {
     _terminate_lock->notify();
   }
 
+  // Thread destructor usually does this.
+  ThreadLocalStorage::set_thread(NULL);
+
   // Deletion must be done synchronously by the JNI DestroyJavaVM thread
   // so that the VMThread deletion completes before the main thread frees
   // up the CodeHeap.