USB: Handle the case of a callback removing its event source

[libsigrok.git] / src / usb.c

diff --git a/src/usb.c b/src/usb.c
index be4eedcf37449899f8f9aa71f9f75e7e17d07a43..fd8bb7a341fd527e6f96c08711b6c37492508a50 100644 (file)
--- a/src/usb.c
+++ b/src/usb.c
@@ -200,33 +200,48 @@ static int usb_callback(int fd, int revents, void *cb_data)
        ctx = cb_data;
 
        start_time = g_get_monotonic_time();
-
        due = ctx->usb_due;
-       timeout = MAX(due - start_time, 0);
-       tv.tv_sec  = timeout / G_USEC_PER_SEC;
-       tv.tv_usec = timeout % G_USEC_PER_SEC;
 
-       sr_spew("libusb_handle_events enter, timeout %g ms", 1e-3 * timeout);
+       if (due > start_time) {
+               timeout = due - start_time;
+               tv.tv_sec  = timeout / G_USEC_PER_SEC;
+               tv.tv_usec = timeout % G_USEC_PER_SEC;
+
+               sr_spew("libusb_handle_events enter: %g ms timeout",
+                       1e-3 * timeout);
+
+               ret = libusb_handle_events_timeout_completed(ctx->libusb_ctx,
+                               (ctx->usb_timeout < 0) ? NULL : &tv, NULL);
+               if (ret != 0) {
+                       /* Warn but still invoke the callback, to give
+                        * the driver a chance to deal with the problem.
+                        */
+                       sr_warn("Error handling libusb event (%s)",
+                               libusb_error_name(ret));
+               }
+               stop_time = g_get_monotonic_time();
 
-       ret = libusb_handle_events_timeout_completed(ctx->libusb_ctx,
-                       (ctx->usb_timeout < 0) ? NULL : &tv, NULL);
-       if (ret != 0) {
-               /* Warn but still invoke the callback, to give the driver
-                * a chance to deal with the problem.
+               sr_spew("libusb_handle_events leave: %g ms elapsed",
+                       1e-3 * (stop_time - start_time));
+               /*
+                * The event source may have been removed by the driver's
+                * libusb transfer callback. Skip the callback in that case.
                 */
-               sr_warn("Error handling libusb event (%s)",
-                       libusb_error_name(ret));
-       }
-       stop_time = g_get_monotonic_time();
+               if (!ctx->usb_source_present)
+                       return TRUE;
+       } else {
+               /* Timeout already expired on entry.
+                */
+               stop_time = start_time;
 
-       sr_spew("libusb_handle_events leave, %g ms elapsed",
-               1e-3 * (stop_time - start_time));
+               sr_spew("libusb_handle_events skipped");
+       }
 
        if (ctx->usb_timeout >= 0)
                ctx->usb_due = stop_time + ctx->usb_timeout;
        /*
-        * Run registered callback to execute any follow-up activity
-        * to libusb event handling.
+        * Run the registered callback to execute any follow-up activity
+        * to libusb's event handling.
         */
        return ctx->usb_cb(-1, (stop_time < due) ? G_IO_IN : 0,
                        ctx->usb_cb_data);
@@ -259,7 +274,8 @@ SR_PRIV int usb_source_add(struct sr_session *session, struct sr_context *ctx,
         * This will have to do for now, until we implement a proper way to
         * deal with libusb events on Windows.
         */
-       ret = sr_session_source_add(session, -2, 0, 0, &usb_callback, ctx);
+       ret = sr_session_source_add_internal(session, NULL, 0,
+                       0, &usb_callback, ctx, (gintptr)ctx->libusb_ctx);
 #else
        const struct libusb_pollfd **lupfd;
        GPollFD *pollfds;
@@ -293,21 +309,8 @@ SR_PRIV int usb_source_add(struct sr_session *session, struct sr_context *ctx,
 
 SR_PRIV int usb_source_remove(struct sr_session *session, struct sr_context *ctx)
 {
-       int ret;
-
-       if (!ctx->usb_source_present)
-               return SR_OK;
-
-#ifdef G_OS_WIN32
-       /* Remove our idle source */
-       sr_session_source_remove(session, -2);
-#else
-       ret = sr_session_source_remove_internal(session,
+       return sr_session_source_remove_internal(session,
                        (gintptr)ctx->libusb_ctx);
-#endif
-       ctx->usb_source_present = FALSE;
-
-       return ret;
 }
 
 SR_PRIV int usb_get_port_path(libusb_device *dev, char *path, int path_len)