Bug 14029

Summary: xcb "Lock assertion failure" in XkbRefreshKeyboardMapping/XkbGetMapChanges
Product: xorg Reporter: Jim Ramsay <i.am>
Component: Lib/XlibAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: 7.3 (2007.09)   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Bug Depends on:    
Bug Blocks: 10101    

Description Jim Ramsay 2008-01-11 12:57:07 UTC 
I have encountered a double 'LockDisplay' situation inside XkbRefreshKeyboardMapping.  It calls LockDisplay, then XkbGetMapChanges:

        ...
        LockDisplay(dpy);
        if ((rtrn=XkbGetMapChanges(dpy,xkbi->desc,&changes))!=Success) {
        ...

Then XKBGetMapChanges *also* calls LockDisplay:

Status
XkbGetMapChanges(Display *dpy,XkbDescPtr xkb,XkbMapChangesPtr changes)
{
    xkbGetMapReq *req;

    if ((dpy->flags & XlibDisplayNoXkb) ||
        (!dpy->xkb_info && !XkbUseExtension(dpy,NULL,NULL)))
        return BadAccess;
    LockDisplay(dpy);
    ...

This only really is a problem when using xcb, due to the more strict  locking assertions.

The actual situation which led me to this discovery occurred in the 'synergys' application (http://synergy2.sourceforge.net/) which gave me the following traceback:

Locking assertion failure.  Backtrace:
#0 /usr/lib/libxcb-xlib.so.0 [0x2aff31e949ec]
#1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_lock+0x15) [0x2aff31e94a77]
#2 /usr/lib/libX11.so.6 [0x2aff30ee8e32]
#3 /usr/lib/libX11.so.6(XkbGetMapChanges+0x3e) [0x2aff30f2bb08]
#4 /usr/lib/libX11.so.6(XkbRefreshKeyboardMapping+0xc7) [0x2aff30f28b4d]
#5 synergys [0x42f4a0]
#6 synergys [0x4311c8]
#7 synergys [0x457ac9]
#8 synergys [0x409206]
#9 synergys [0x4094ab]
#10 synergys [0x409ced]
#11 /lib/libc.so.6(__libc_start_main+0xf4) [0x2aff319681f4]
#12 synergys(__gxx_personality_v0+0x1e9) [0x4063c9]
synergys: xcb_xlib.c:73: xcb_xlib_lock: Assertion `!c->xlib.lock' failed.
Aborted
Comment 1 Adam Jackson 2008-02-24 16:58:19 UTC 
I had this patched in Fedora, thought I'd fixed it upstream too, but I guess not.

Fixed now anyway.  Thanks!

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