Patch for Review: Thread.interrupt() for MinGW

[Mohan Embar <gnustuff at thisiscool dot com>]

Hi People,

This patch attempts to implement Thread.interrupt() on MinGW.

Two disclaimers: this does not support interrupting blocking I/O
operations. Ironically, I had started to implement this because
I wanted interruptible I/O, but these posts from Bryce convinced
me to walk away from this:

- http://gcc.gnu.org/ml/java/2003-09/msg00066.html

and particularly, this:

- http://gcc.gnu.org/ml/java/2000-q1/msg00419.html

Secondly, I haven't addressed _Jv_select() yet. I'll do that when
Michael is further along with the NIO stuff.

I've attached a testcase.

Your review and feedback is appreciated. Thanks in advance.

-- Mohan
http://www.thisiscool.com/
http://www.animalsong.org/


ChangeLog
2003-09-15  Mohan Embar  <gnustuff@thisiscool.com>

	* win32-threads.cc: (ensure_interrupt_event_initialized) New
	function for lazy initialization of an auto-reset event.
	(_Jv_CondWait) Added thread interrupt support.
	(_Jv_ThreadInitData) Added initialization of interrupt support
	members.
	(_Jv_ThreadDestroyData) Added cleanup of interrupt support members.
	(_Jv_ThreadStart) Removed unused code.
	(_Jv_GetInterruptEvent) New method for returning interrupt event
	to an external caller.
	(_Jv_ThreadInterrupt) Implemented.
	* include/win32-threads.h: (_Jv_Thread_t) Added a Win32 auto-reset
	event for interrupt support as well as a mutex which regulates
	access to this.
	(_Jv_GetInterruptEvent) Declared new method for returning interrupt
	event to an external caller.
	* java/lang/natWin32Process.cc: (cleanup) Close handle to spawned
	process.
	(waitFor) Added interrupt support.

Index: win32-threads.cc
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/win32-threads.cc,v
retrieving revision 1.9
diff -u -2 -r1.9 win32-threads.cc
--- win32-threads.cc	28 Jan 2003 22:23:36 -0000	1.9
+++ win32-threads.cc	15 Sep 2003 06:45:01 -0000
@@ -82,4 +82,14 @@
 }
 
+inline void
+ensure_interrupt_event_initialized(HANDLE& rhEvent)
+{
+  if (!rhEvent)
+    {
+      rhEvent = CreateEvent (NULL, 0, 0, NULL);
+      if (!rhEvent) JvFail("CreateEvent() failed");
+    }
+}
+
 // Reimplementation of the general algorithm described at
 // http://www.cs.wustl.edu/~schmidt/win32-cv-1.html (isomorphic to
@@ -92,4 +102,19 @@
     return _JV_NOT_OWNER;
 
+  _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
+  java::lang::Thread *current_obj = _Jv_ThreadCurrent ();
+
+  // Now that we hold the interrupt mutex, check if this thread has been 
+  // interrupted already.
+  EnterCriticalSection (&current->interrupt_mutex);
+  ensure_interrupt_event_initialized (current->interrupt_event);
+  jboolean interrupted = current_obj->interrupt_flag;
+  LeaveCriticalSection (&current->interrupt_mutex);
+
+  if (interrupted)
+    {
+      return _JV_INTERRUPTED;
+    }
+
   EnterCriticalSection (&cv->count_mutex);
   ensure_condvar_initialized (cv);
@@ -104,5 +129,29 @@
   _Jv_MutexUnlock (mu);
 
-  DWORD rval = WaitForMultipleObjects (2, &(cv->ev[0]), 0, time);
+  // Set up our array of three events:
+  // - the auto-reset event (for notify())
+  // - the manual-reset event (for notifyAll())
+  // - the interrupt event (for interrupt())
+  // We wait for any one of these to be signaled.
+  HANDLE arh[3];
+  arh[0] = cv->ev[0];
+  arh[1] = cv->ev[1];
+  arh[2] = current->interrupt_event;
+  DWORD rval = WaitForMultipleObjects (3, arh, 0, time);
+
+  EnterCriticalSection (&current->interrupt_mutex);
+
+  // If we were unblocked by the third event (our thread's interrupt
+  // event), set the thread's interrupt flag. I think this sanity
+  // check guards against someone resetting our interrupt flag
+  // in the time between when interrupt_mutex is released in
+  // _Jv_ThreadInterrupt and the interval of time between the
+  // WaitForMultipleObjects call we just made and our acquisition
+  // of interrupt_mutex.
+  if (rval == (WAIT_OBJECT_0 + 2))
+    current_obj->interrupt_flag = true;
+    
+  interrupted = current_obj->interrupt_flag;
+  LeaveCriticalSection (&current->interrupt_mutex);
 
   EnterCriticalSection(&cv->count_mutex);
@@ -117,6 +166,6 @@
 
   _Jv_MutexLock (mu);
-
-  return 0;
+  
+  return interrupted ? _JV_INTERRUPTED : 0;
 }
 
@@ -198,4 +247,6 @@
   data->flags = 0;
   data->thread_obj = obj;
+  data->interrupt_event = 0;
+  InitializeCriticalSection (&data->interrupt_mutex);
 
   return data;
@@ -205,4 +256,7 @@
 _Jv_ThreadDestroyData (_Jv_Thread_t *data)
 {
+  DeleteCriticalSection (&data->interrupt_mutex);
+  if (data->interrupt_event)
+    CloseHandle(data->interrupt_event);
   _Jv_Free(data);
 }
@@ -309,9 +363,6 @@
     data->flags |= FLAG_DAEMON;
 
-  HANDLE h = GC_CreateThread(NULL, 0, really_start, info, 0, &id);
+  GC_CreateThread(NULL, 0, really_start, info, 0, &id);
   _Jv_ThreadSetPriority(data, thread->getPriority());
-
-  //if (!h)
-    //JvThrow ();
 }
 
@@ -327,8 +378,26 @@
 }
 
+//
+// Interrupt support
+//
+
+HANDLE
+_Jv_GetInterruptEvent (void)
+{
+  _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
+  EnterCriticalSection (&current->interrupt_mutex);
+  ensure_interrupt_event_initialized (current->interrupt_event);
+  HANDLE hEvent = current->interrupt_event;
+  LeaveCriticalSection (&current->interrupt_mutex);
+  return hEvent;
+}
+
 void
 _Jv_ThreadInterrupt (_Jv_Thread_t *data)
 {
-  MessageBox(NULL, "Unimplemented", "win32-threads.cc:_Jv_ThreadInterrupt", MB_OK);
-  // FIXME:
+  EnterCriticalSection (&data->interrupt_mutex);
+  ensure_interrupt_event_initialized (data->interrupt_event);
+  data->thread_obj->interrupt_flag = true;
+  SetEvent (data->interrupt_event);
+  LeaveCriticalSection (&data->interrupt_mutex);
 }
Index: include/win32-threads.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/include/win32-threads.h,v
retrieving revision 1.7
diff -u -2 -r1.7 win32-threads.h
--- include/win32-threads.h	28 Jan 2003 22:23:36 -0000	1.7
+++ include/win32-threads.h	15 Sep 2003 06:45:04 -0000
@@ -51,4 +51,12 @@
   int flags;            // Flags are defined in implementation.
   HANDLE handle;        // Actual handle to the thread
+
+  // Protects access to the thread's interrupt_flag and
+  // interrupt_event variables within this module.
+  CRITICAL_SECTION interrupt_mutex;
+  
+  // A Win32 auto-reset event for thread interruption
+  HANDLE interrupt_event;
+
   java::lang::Thread *thread_obj;
 } _Jv_Thread_t;
@@ -150,4 +158,22 @@
 void _Jv_ThreadWait (void);
 void _Jv_ThreadInterrupt (_Jv_Thread_t *data);
+
+//
+// Thread interruption support
+//
+
+// Gets the auto-reset event for the current thread which is
+// signalled by _Jv_ThreadInterrupt. The caller can wait on this
+// event in addition to other waitable objects.
+//
+// NOTE: After waiting on this event with WaitForMultipleObjects,
+// you should ALWAYS use the return value of WaitForMultipleObjects
+// to test whether this event was signalled and whether thread
+// interruption has occurred. You should do this instead of checking
+// the thread's interrupted_flag, because someone could have reset
+// this flag in the interval of time between the return of
+// WaitForMultipleObjects and the time you query interrupted_flag.
+// See java/lang/natWin32Process.cc (waitFor) for an example.
+HANDLE _Jv_GetInterruptEvent (void);
 
 // Remove defines from <windows.h> that conflict with various things in libgcj code
Index: java/lang/natWin32Process.cc
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/java/lang/natWin32Process.cc,v
retrieving revision 1.5
diff -u -2 -r1.5 natWin32Process.cc
--- java/lang/natWin32Process.cc	29 Aug 2003 04:21:00 -0000	1.5
+++ java/lang/natWin32Process.cc	15 Sep 2003 06:45:06 -0000
@@ -47,4 +47,9 @@
       errorStream = NULL;
     }
+  if (procHandle)
+    {
+      CloseHandle((HANDLE) procHandle);
+      procHandle = (jint) INVALID_HANDLE_VALUE;
+    }
 }
 
@@ -93,6 +98,25 @@
       DWORD exitStatus = 0UL;
 
-      // FIXME: The wait should be interruptible.
-      WaitForSingleObject ((HANDLE) procHandle, INFINITE);
+      // Set up our waitable objects array
+      // - 0: the handle to the process we just launched
+      // - 1: our thread's interrupt event
+      HANDLE arh[2];
+      arh[0] = (HANDLE) procHandle;
+      arh[1] = _Jv_GetInterruptEvent ();
+      DWORD rval = WaitForMultipleObjects (2, arh, 0, INFINITE);
+
+      // Use the returned value from WaitForMultipleObjects
+      // instead of our thread's interrupt_flag to test for
+      // thread interruption. See the comment for _Jv_GetInterruptEvent().
+      bool bInterrupted = rval == (WAIT_OBJECT_0 + 1);
+      
+      if (bInterrupted)
+        {
+          // Querying this forces a reset our thread's interrupt flag.
+          Thread::interrupted();
+          
+          cleanup ();
+          throw new InterruptedException ();
+        }
 
       GetExitCodeProcess ((HANDLE) procHandle, &exitStatus);

Attachment: InterruptTest.tar.bz2
Description: application/bzip2