From 52426ce4a929f7e1389baf490967fc02357b3f5e Mon Sep 17 00:00:00 2001 From: Adam Jackson Date: Tue, 5 Mar 2019 15:31:51 -0500 Subject: [PATCH] drisw: Try harder to probe whether MIT-SHM works XQueryExtension merely tells you whether the extension exists, it doesn't tell you whether you're local enough for it to work. XShmQueryVersion is not enough to discover this either, you need to provoke the server to do actual work, and if it thinks you're remote it will throw BadRequest at you. So send an invalid ShmDetach and use the error code to distinguish local from remote. [airlied: fixed bug not resetting xshm_error to 0 on success, which made later stuff fail completely.] Reviewed-by: Eric Anholt Reviewed-by: Dave Airlie Signed-off-by: Adam Jackson --- src/glx/drisw_glx.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/src/glx/drisw_glx.c b/src/glx/drisw_glx.c index c63b097..f38dbbc 100644 --- a/src/glx/drisw_glx.c +++ b/src/glx/drisw_glx.c @@ -73,11 +73,10 @@ handle_xerror(Display *dpy, XErrorEvent *event) (void) dpy; assert(xshm_opcode != -1); - if (event->request_code != xshm_opcode || - event->minor_code != X_ShmAttach) + if (event->request_code != xshm_opcode) return 0; - xshm_error = 1; + xshm_error = event->error_code; return 0; } @@ -826,9 +825,27 @@ driswBindExtensions(struct drisw_screen *psc, const __DRIextension **extensions) static int check_xshm(Display *dpy) { + int (*old_handler)(Display *, XErrorEvent *); + int ignore; + XShmSegmentInfo info = { 0, }; + + if (!XQueryExtension(dpy, "MIT-SHM", &xshm_opcode, &ignore, &ignore)) + return False; + + old_handler = XSetErrorHandler(handle_xerror); + XShmDetach(dpy, &info); + XSync(dpy, False); + (void) XSetErrorHandler(old_handler); - return XQueryExtension(dpy, "MIT-SHM", &xshm_opcode, &ignore, &ignore); + /* BadRequest means we're a remote client. If we were local we'd + * expect BadValue since 'info' has an invalid segment name. + */ + if (xshm_error == BadRequest) + return False; + + xshm_error = 0; + return True; } static struct glx_screen * -- 2.7.4