Updated Signal Handler (#287)

https://github.com/PowerShell/Win32-OpenSSH/issues/1096
https://github.com/PowerShell/Win32-OpenSSH/issues/191

- Updated wait_for_multiple_objects_enhanced() to handle a no-event request while alterable.
- Simplified wait_for_any_event() to by taking advantage of no-event alterable request in wait_for_multiple_objects_enhanced().
- Updated wait_for_any_event() to use MAX_CHILDREN limit instead of MAXIMUM_WAIT_OBJECTS limit.
- Removed unnecessary ZeroMemory() call.
- Created distinct definition MAXIMUM_WAIT_OBJECTS_ENHANCED
 and modified functions to use it.
- Upped w32_select() event limit.
- Modified wait_for_multiple_objects_enhanced() to allow for 0 millisecond wait.

contrib/win32/win32compat/signal.c

@@ -260,59 +260,42 @@ sw_process_pending_signals()
 int
 wait_for_any_event(HANDLE* events, int num_events, DWORD milli_seconds)
 {
-	HANDLE all_events[MAXIMUM_WAIT_OBJECTS];
-	DWORD num_all_events;
+	HANDLE all_events[MAXIMUM_WAIT_OBJECTS_ENHANCED];
 	DWORD live_children = children.num_children - children.num_zombies;
+	DWORD num_all_events = num_events + live_children;
 	errno_t r = 0;
 
-	num_all_events = num_events + live_children;
-
-	if (num_all_events > MAXIMUM_WAIT_OBJECTS) {
-		debug3("wait() - ERROR max events reached");
+	if (num_all_events > MAXIMUM_WAIT_OBJECTS_ENHANCED) {
+		debug3("wait_for_any_event() - ERROR max events reached");
 		errno = ENOTSUP;
 		return -1;
 	}
 
-	if ((r = memcpy_s(all_events, MAXIMUM_WAIT_OBJECTS * sizeof(HANDLE), children.handles, live_children * sizeof(HANDLE)) != 0) ||
-	( r = memcpy_s(all_events + live_children, (MAXIMUM_WAIT_OBJECTS - live_children) * sizeof(HANDLE), events, num_events * sizeof(HANDLE)) != 0)) {
+	if ((r = memcpy_s(all_events, MAXIMUM_WAIT_OBJECTS_ENHANCED * sizeof(HANDLE), children.handles, live_children * sizeof(HANDLE)) != 0) ||
+	( r = memcpy_s(all_events + live_children, (MAXIMUM_WAIT_OBJECTS_ENHANCED - live_children) * sizeof(HANDLE), events, num_events * sizeof(HANDLE)) != 0)) {
 		debug3("memcpy_s failed with error: %d.", r);
 		return -1;
 	}
 
 	debug5("wait() on %d events and %d children", num_events, live_children);
-	/* TODO - implement signal catching and handling */
-	if (num_all_events) {
-		DWORD ret = wait_for_multiple_objects_enhanced(num_all_events, all_events, milli_seconds, TRUE);
-		if ((ret >= WAIT_OBJECT_0_ENHANCED) && (ret <= WAIT_OBJECT_0_ENHANCED + num_all_events - 1)) {
-			/* woken up by event signalled
-			 * is this due to a child process going down
-			 */
-			if (live_children && ((ret - WAIT_OBJECT_0_ENHANCED) < live_children)) {
-				sigaddset(&pending_signals, W32_SIGCHLD);
-				sw_child_to_zombie(ret - WAIT_OBJECT_0_ENHANCED);
-			}
-		} else if (ret == WAIT_IO_COMPLETION_ENHANCED) {
-			/* APC processed due to IO or signal*/
-		} else if (ret == WAIT_TIMEOUT_ENHANCED) {
-			/* timed out */
-			return 0;
-		} else { /* some other error*/
-			errno = EOTHER;
-			debug3("ERROR: unxpected wait end: %d", ret);
-			return -1;
-		}
-	} else {
-		DWORD ret = SleepEx(milli_seconds, TRUE);
-		if (ret == WAIT_IO_COMPLETION) {
-			/* APC processed due to IO or signal*/
-		} else if (ret == 0) {
-			/* timed out */
-			return 0;
-		} else { /* some other error */
-			errno = EOTHER;
-			debug3("ERROR: unxpected SleepEx error: %d", ret);
-			return -1;
+	DWORD ret = wait_for_multiple_objects_enhanced(num_all_events, all_events, milli_seconds, TRUE);
+	if ((ret >= WAIT_OBJECT_0_ENHANCED) && (ret <= WAIT_OBJECT_0_ENHANCED + num_all_events - 1)) {
+		/* woken up by event signaled
+		 * is this due to a child process going down
+		 */
+		if (live_children && ((ret - WAIT_OBJECT_0_ENHANCED) < live_children)) {
+			sigaddset(&pending_signals, W32_SIGCHLD);
+			sw_child_to_zombie(ret - WAIT_OBJECT_0_ENHANCED);
 		}
+	} else if (ret == WAIT_IO_COMPLETION_ENHANCED) {
+		/* APC processed due to IO or signal*/
+	} else if (ret == WAIT_TIMEOUT_ENHANCED) {
+		/* timed out */
+		return 0;
+	} else { /* some other error*/
+		errno = EOTHER;
+		debug3("ERROR: unexpected wait end: %d", ret);
+		return -1;
 	}
 
 	if (pending_signals)

contrib/win32/win32compat/signal_internal.h

@@ -1,12 +1,12 @@
 #include <Windows.h>
 
 /* child processes */
-#define MAX_CHILDREN 500
+#define MAX_CHILDREN 512
 
 struct _children {
 	/* 
 	 * array of handles and process_ids. 
-	 * intial (num_children - num_zombies) are alive 
+	 * initial (num_children - num_zombies) are alive 
 	 * rest are zombies 
 	 */
 	HANDLE handles[MAX_CHILDREN];
@@ -32,6 +32,7 @@ struct _timer_info {
 };
 int sw_init_timer();
 
+#define MAXIMUM_WAIT_OBJECTS_ENHANCED 1024
 #define WAIT_OBJECT_0_ENHANCED 0x00000000
 #define WAIT_ABANDONED_0_ENHANCED 0x10000000
 #define WAIT_TIMEOUT_ENHANCED 0x20000000

contrib/win32/win32compat/signal_wait.c

@@ -73,15 +73,34 @@ DWORD
 wait_for_multiple_objects_enhanced(_In_ DWORD  nCount, _In_ const HANDLE *lpHandles,
 	_In_ DWORD dwMilliseconds, _In_ BOOL bAlertable)
 {
-	
 	/* number of separate bins / threads required to monitor execution */
 	const DWORD bin_size = MAXIMUM_WAIT_OBJECTS;
 	const DWORD bins_total = (nCount - 1) / bin_size + 1;
 	
 	DWORD return_value = WAIT_FAILED_ENHANCED;
 	HANDLE wait_event = NULL;
-	wait_for_multiple_objects_struct *wait_bins = NULL;
+	wait_for_multiple_objects_struct wait_bins[(MAXIMUM_WAIT_OBJECTS_ENHANCED - 1) / MAXIMUM_WAIT_OBJECTS + 1] = { 0 };
 	DWORD wait_ret;
+
+	/* protect against too many events */
+	if (nCount > MAXIMUM_WAIT_OBJECTS_ENHANCED)
+	{
+		return WAIT_FAILED_ENHANCED;
+	}
+
+	/* in the event that no events are passed and alterable, just do a sleep and
+	 * and wait for wakeup call.  This differs from the WaitForMultipleObjectsEx
+	 * call which would return an error if no events are passed to the function. */
+	if (nCount == 0 && bAlertable)
+	{
+		DWORD wait_ret = SleepEx(dwMilliseconds, TRUE);
+		if (wait_ret == 0)
+			return WAIT_TIMEOUT_ENHANCED;
+		else if (wait_ret == WAIT_IO_COMPLETION) 
+			return WAIT_IO_COMPLETION_ENHANCED;
+		else
+			return WAIT_FAILED_ENHANCED;
+	}
 	
 	/* if less than the normal maximum then just use the built-in function
 	 * to avoid the overhead of another thread */
@@ -108,21 +127,12 @@ wait_for_multiple_objects_enhanced(_In_ DWORD  nCount, _In_ const HANDLE *lpHand
 		return WAIT_FAILED_ENHANCED;
 	}
 
-
 	/* setup synchronization event to flag when the main thread should wake up */
 	wait_event = CreateEvent(NULL, TRUE, FALSE, NULL);
 	if (wait_event == NULL) {
 		goto cleanup;
 	}
 
-	/* allocate an area to communicate with our threads */
-	wait_bins = (wait_for_multiple_objects_struct *)
-		calloc(bins_total, sizeof(wait_for_multiple_objects_struct));
-	if (wait_bins == NULL) {
-		goto cleanup;
-	}
-
-	ZeroMemory(wait_bins, bins_total * sizeof(wait_for_multiple_objects_struct));
 	/* initialize each thread that handles up to MAXIMUM_WAIT_OBJECTS each */
 	for (DWORD bin = 0; bin < bins_total; bin++) {
 
@@ -220,7 +230,5 @@ cleanup:
 
 	if (wait_event)
 		CloseHandle(wait_event);
-	if (wait_bins)
-		free(wait_bins);
 	return return_value;
 }

contrib/win32/win32compat/w32fd.c

@@ -654,7 +654,7 @@ w32_fcntl(int fd, int cmd, ... /* arg */)
 	return ret;
 }
 
-#define SELECT_EVENT_LIMIT 32
+#define SELECT_EVENT_LIMIT 512
 int
 w32_select(int fds, w32_fd_set* readfds, w32_fd_set* writefds, w32_fd_set* exceptfds, const struct timeval *timeout)
 {