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drisw: Try harder to probe whether MIT-SHM works

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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 <eric@anholt.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
This commit is contained in:
Adam Jackson 2019-03-05 15:31:51 -05:00 • committed by Dave Airlie
parent 50f3535d1f
commit 52426ce4a9
1 changed files with 22 additions and 5 deletions
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27
src/glx/drisw_glx.c
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@ -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 ignore;
int (*old_handler)(Display *, XErrorEvent *);
return XQueryExtension(dpy, "MIT-SHM", &xshm_opcode, &ignore, &ignore);
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);
/* 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 *