gc4.13 tarball importgc4_13

1 files changed, 45 insertions, 10 deletions

diff --git a/win32_threads.c b/win32_threads.c
index eb485bdc..2b01c5c6 100755
--- a/win32_threads.c
+++ b/win32_threads.c
@@ -8,22 +8,32 @@
 #define MAX_THREADS 64
 
 struct thread_entry {
+  LONG in_use;
   DWORD id;
   HANDLE handle;
-  void *stack;   /* The cold end of the stack. */
+  void *stack;		/* The cold end of the stack.   */
+			/* 0 ==> entry not valid.	*/
+			/* !in_use ==> stack == 0	*/
   CONTEXT context;
+  GC_bool suspended;
 };
 
-struct thread_entry thread_table[MAX_THREADS];
+volatile GC_bool GC_please_stop = FALSE;
+
+volatile struct thread_entry thread_table[MAX_THREADS];
 
 void GC_stop_world()
 {
   DWORD thread_id = GetCurrentThreadId();
   int i;
+
+  GC_please_stop = TRUE;
   for (i = 0; i < MAX_THREADS; i++)
-    if (thread_table[i].stack != 0 && thread_table[i].id != thread_id) {
+    if (thread_table[i].stack != 0
+	&& thread_table[i].id != thread_id) {
       if (SuspendThread(thread_table[i].handle) == (DWORD)-1)
 	ABORT("SuspendThread failed");
+      thread_table[i].suspended = TRUE;
     }
 }
 
@@ -32,10 +42,13 @@ void GC_start_world()
   DWORD thread_id = GetCurrentThreadId();
   int i;
   for (i = 0; i < MAX_THREADS; i++)
-    if (thread_table[i].stack != 0 && thread_table[i].id != thread_id) {
+    if (thread_table[i].stack != 0 && thread_table[i].suspended
+	&& thread_table[i].id != thread_id) {
       if (ResumeThread(thread_table[i].handle) == (DWORD)-1)
 	ABORT("ResumeThread failed");
+      thread_table[i].suspended = FALSE;
     }
+  GC_please_stop = FALSE;
 }
 
 ptr_t GC_current_stackbottom()
@@ -117,20 +130,34 @@ BOOL WINAPI DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved)
   switch (reason) {
   case DLL_PROCESS_ATTACH:
     InitializeCriticalSection(&GC_allocate_ml);
+    GC_init();	/* Force initialization before thread attach.	*/
     /* fall through */
   case DLL_THREAD_ATTACH:
     {
       int i;
-      LOCK();
+      /* It appears to be unsafe to acquire a lock here, since this	*/
+      /* code is apparently not preeemptible on some systems.		*/
+      /* (This is based on complaints, not on Microsoft's official	*/
+      /* documentation, which says this should perform "only simple	*/
+      /* inititalization tasks".)					*/
+      /* Hence we make do with nonblocking synchronization.		*/
+
       /* The following should be a noop according to the win32	*/
       /* documentation.  There is empirical evidence that it	*/
       /* isn't.		- HB					*/
-      if (GC_incremental) SetUnhandledExceptionFilter(GC_write_fault_handler);
-      for (i = 0; thread_table[i].stack != 0; i++) {
+#     ifndef SMALL_CONFIG
+       if (GC_incremental) SetUnhandledExceptionFilter(GC_write_fault_handler);
+#     endif
+
+      for (i = 0; InterlockedExchange(&thread_table[i].in_use,1) != 0; i++) {
+	/* Compare-and-swap would make this cleaner, but that's not 	*/
+	/* supported before Windows 98 and NT 4.0.  In Windows 2000,	*/
+	/* InterlockedExchange is supposed to be replaced by		*/
+	/* InterlockedExchangePointer, but that's not really what I	*/
+	/* want here.							*/
 	if (i == MAX_THREADS - 1)
 	  ABORT("too many threads");
       }
-      thread_table[i].stack = GC_get_stack_base();
       thread_table[i].id = GetCurrentThreadId();
       if (!DuplicateHandle(GetCurrentProcess(),
 	                   GetCurrentThread(),
@@ -143,7 +170,11 @@ BOOL WINAPI DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved)
 	    GC_printf1("Last error code: %lx\n", last_error);
 	    ABORT("DuplicateHandle failed");
       }
-      UNLOCK();
+      thread_table[i].stack = GC_get_stack_base();
+      /* If this thread is being created while we are trying to stop	*/
+      /* the world, wait here.  Hopefully this can't happen on any	*/
+      /* systems that don't allow us to block here.			*/
+      while (GC_please_stop) Sleep(20);
     }
     break;
   case DLL_PROCESS_DETACH:
@@ -152,10 +183,14 @@ BOOL WINAPI DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved)
       int i;
       DWORD thread_id = GetCurrentThreadId();
       LOCK();
-      for (i = 0; thread_table[i].stack == 0 || thread_table[i].id != thread_id; i++)
+      for (i = 0;
+           thread_table[i].stack == 0 || thread_table[i].id != thread_id;
+	   i++) {
 	if (i == MAX_THREADS - 1)
 	  ABORT("thread not found on detach");
+      }
       thread_table[i].stack = 0;
+      thread_table[i].in_use = FALSE;
       CloseHandle(thread_table[i].handle);
       BZERO(&thread_table[i].context, sizeof(CONTEXT));
       UNLOCK();