[Spice-devel] UsbDk-related patches

[Christophe Fergeau]

On Wed, Jan 27, 2016 at 02:09:25PM +0200, Dmitry Fleytman wrote:
> 
> > On 27 Jan 2016, at 14:00 PM, Christophe Fergeau <cfergeau at redhat.com> wrote:
> > 
> > On Wed, Jan 27, 2016 at 01:51:12PM +0200, Dmitry Fleytman wrote:
> >> Hello, Spice List
> >> 
> >> I just got a confirmation that UsbDk backend integration for libusb was pushed upstream:
> >> 
> >> 24c5289 build: Integrate usbdk backend
> >> 8823c17 usbdk: Introduce usbdk backend
> >> 5d83aba windows: Rename windows_usb.h/c windows_winusb.h/c
> >> 92a3278 windows: Move common definitions to a separate file
> >> 
> >> (see at https://github.com/libusb/libusb/commits/master)
> > 
> > Didn't
> > https://github.com/libusb/libusb/commit/cdfe236931ef3fd06adac0fdf6df49baa39ff35e
> > reintroduce the bug where if there are usbdk issues,
> > libusb_init() will fail the first time it's called, and then report
> > success without doing any initialisation?
> 
> (looping Chris)
> 
> Hi Chris, 
> 
> There is an opinion that commit
> (https://github.com/libusb/libusb/commit/cdfe236931ef3fd06adac0fdf6df49baa39ff35e)
> is problematic (see above). If so, there is the symmetrical problem
> with WinUsb backend as well. What do you think?

The WinUsb backend is doing things slightly differently, and looks more
correct, something like:
(not sure how bad it is to call window_common_exit() when windows_common_init()
hasn't been called, this can happen with this patch if load_usbdk_helper_dll fails)

diff --git a/libusb/os/windows_usbdk.c b/libusb/os/windows_usbdk.c
index 9abb83e..2b97f69 100644
--- a/libusb/os/windows_usbdk.c
+++ b/libusb/os/windows_usbdk.c
@@ -195,25 +195,30 @@ error_unload:
 
 static int usbdk_init(struct libusb_context *ctx)
 {
-       int r;
+       int r = LIBUSB_ERROR_OTHER;
 
        if (++concurrent_usage == 0) {
                r = load_usbdk_helper_dll(ctx);
                if (r)
-                       return r;
+                       goto init_exit;
 
                init_polling();
 
                r = windows_common_init(ctx);
                if (r)
-                       goto error_roll_back;
+                       goto init_exit;
        }
 
-       return LIBUSB_SUCCESS;
+       r = LIBUSB_SUCCESS;
+
+init_exit:
+       if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
+               windows_common_exit();
+               unload_usbdk_helper_dll();
+
+       if (r != LIBUSB_SUCCESS)
+               --concurrent_usage;
 
-error_roll_back:
-       windows_common_exit();
-       unload_usbdk_helper_dll();
        return r;
 }

Christophe
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