core: Add helper functions to signal and clear the event pipe

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

libusb/core.c

@@ -1172,18 +1172,50 @@ void API_EXPORTED libusb_unref_device(libusb_device *dev)
 }
 
 /*
- * Interrupt the iteration of the event handling thread, so that it picks
- * up the new fd.
+ * Signal the event pipe so that the event handling thread will be
+ * interrupted to process an internal event.
  */
-void usbi_fd_notification(struct libusb_context *ctx)
+int usbi_signal_event(struct libusb_context *ctx)
 {
 	unsigned char dummy = 1;
 	ssize_t r;
 
 	/* write some data on event pipe to interrupt event handlers */
 	r = usbi_write(ctx->event_pipe[1], &dummy, sizeof(dummy));
-	if (r != sizeof(dummy))
+	if (r != sizeof(dummy)) {
 		usbi_warn(ctx, "internal signalling write failed");
+		return LIBUSB_ERROR_IO;
+	}
+
+	return 0;
+}
+
+/*
+ * Clear the event pipe so that the event handling will no longer be
+ * interrupted.
+ */
+int usbi_clear_event(struct libusb_context *ctx)
+{
+	unsigned char dummy;
+	ssize_t r;
+
+	/* read some data on event pipe to clear it */
+	r = usbi_read(ctx->event_pipe[0], &dummy, sizeof(dummy));
+	if (r != sizeof(dummy)) {
+		usbi_warn(ctx, "internal signalling read failed");
+		return LIBUSB_ERROR_IO;
+	}
+
+	return 0;
+}
+
+/*
+ * Interrupt the iteration of the event handling thread, so that it picks
+ * up the new fd.
+ */
+void usbi_fd_notification(struct libusb_context *ctx)
+{
+	usbi_signal_event(ctx);
 }
 
 /** \ingroup dev
@@ -1384,8 +1416,6 @@ static void do_close(struct libusb_context *ctx,
 void API_EXPORTED libusb_close(libusb_device_handle *dev_handle)
 {
 	struct libusb_context *ctx;
-	unsigned char dummy = 1;
-	ssize_t r;
 
 	if (!dev_handle)
 		return;
@@ -1404,24 +1434,14 @@ void API_EXPORTED libusb_close(libusb_device_handle *dev_handle)
 	ctx->device_close++;
 	usbi_mutex_unlock(&ctx->event_data_lock);
 
-	/* write some data on event pipe to interrupt event handlers */
-	r = usbi_write(ctx->event_pipe[1], &dummy, sizeof(dummy));
-	if (r <= 0) {
-		usbi_warn(ctx, "internal signalling write failed, closing anyway");
-		do_close(ctx, dev_handle);
-		usbi_mutex_lock(&ctx->event_data_lock);
-		ctx->device_close--;
-		usbi_mutex_unlock(&ctx->event_data_lock);
-		return;
-	}
+	/* signal the event pipe to interrupt event handlers */
+	usbi_signal_event(ctx);
 
 	/* take event handling lock */
 	libusb_lock_events(ctx);
 
-	/* read the dummy data */
-	r = usbi_read(ctx->event_pipe[0], &dummy, sizeof(dummy));
-	if (r <= 0)
-		usbi_warn(ctx, "internal signalling read failed, closing anyway");
+	/* clear the event pipe */
+	usbi_clear_event(ctx);
 
 	/* Close the device */
 	do_close(ctx, dev_handle);

libusb/io.c

@@ -2051,8 +2051,6 @@ redo_poll:
 		/* another thread wanted to interrupt event handling, and it succeeded!
 		 * handle any other events that cropped up at the same time, and
 		 * simply return */
-		ssize_t ret;
-		unsigned char dummy;
 		unsigned int ru;
 
 		usbi_dbg("caught a fish on the event pipe");
@@ -2063,13 +2061,9 @@ redo_poll:
 		ru = ctx->device_close;
 		usbi_mutex_unlock(&ctx->event_data_lock);
 		if (!ru) {
-			ret = usbi_read(ctx->event_pipe[0], &dummy, sizeof(dummy));
-			if (ret != sizeof(dummy)) {
-				usbi_err(ctx, "event pipe read error %d err=%d",
-					 ret, errno);
-				r = LIBUSB_ERROR_OTHER;
+			r = usbi_clear_event(ctx);
+			if (r)
 				goto handled;
-			}
 		}
 
 		if (0 == --r)

libusb/libusbi.h

@@ -462,6 +462,9 @@ int usbi_get_config_index_by_value(struct libusb_device *dev,
 void usbi_connect_device (struct libusb_device *dev);
 void usbi_disconnect_device (struct libusb_device *dev);
 
+int usbi_signal_event(struct libusb_context *ctx);
+int usbi_clear_event(struct libusb_context *ctx);
+
 /* Internal abstraction for poll (needs struct usbi_transfer on Windows) */
 #if defined(OS_LINUX) || defined(OS_DARWIN) || defined(OS_OPENBSD) || defined(OS_NETBSD) || defined(OS_HAIKU)
 #include <unistd.h>

libusb/version_nano.h

@@ -1 +1 @@
-#define LIBUSB_NANO 10935
+#define LIBUSB_NANO 10936