605c778e69
As you know there are some nasty libs / apps doing locking
incorrectly. In order to improve the information given to the user
when he encounters such a situation (people don't run apps in gdb
normally) I created the patch attached.
It's very non-intrusive (and affects only xlib/xcb, Josh told me on
irc that it could be useful for other areas too, personally I don't
think that it's really needed at other places ...).
Some same outputs and the discussion of them:
lxuser@pdln:/tmp$ ./main
Got a backtrace:
#0 /tmp/usr/lib/libxcb-xlib.so.0 [0xb7f9d728]
#1 /tmp/usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x31) [0xb7f9d861]
#2 ./test.so(function_a+0x11) [0xb7f9f3fd]
#3 ./test.so(function_b+0x11) [0xb7f9f410]
#4 ./main [0x80484a7]
#5 /lib/libc.so.6(__libc_start_main+0xdc) [0xb7e60ebc]
#6 ./main [0x80483f1]
main: xcb_xlib.c:82: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.
Aborted
That's kinda the normal situation.
lxuser@pdln:/tmp$ ./main
Got a backtrace:
#0 /tmp/usr/lib/libxcb-xlib.so.0 [0xb7f90728]
#1 /tmp/usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x31) [0xb7f90861]
#2 /tmp/test.so [0xb7f923cd]
#3 /tmp/test.so(function_b+0x11) [0xb7f923e0]
#4 ./main [0x80484ab]
#5 /lib/libc.so.6(__libc_start_main+0xdc) [0xb7e53ebc]
#6 ./main [0x80483f1]
main: xcb_xlib.c:82: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.
Aborted
There are two possible reasons that the name doesn't appear in #2:
a) a hidden symbol or a symbol with statical linkage in a library
b) a symbol in an app not compiled with -rdynamic.
But in both cases you still know _where_ the caller is.
Note that in this example test.so was compiled with
-fomit-frame-pointer; this isn't an issue as _one_ (= the caller)
stack trace is still valid (as long as you don't have the insane idea
to compile xcb with -fo-f-p).
Another issue that may appear is "tail call elimination" (some entries
are mysteriously missing; this is quite ugly, but you still get enough
information so that you can do something useful with the issue e.g. by
disassembling the relevant parts with gdb).
Signed-off-by: Jamey Sharp <jamey@minilop.net>
|
||
|---|---|---|
| doc | ||
| src | ||
| tests | ||
| tools | ||
| .gitignore | ||
| COPYING | ||
| INSTALL | ||
| Makefile.am | ||
| NEWS | ||
| README | ||
| acinclude.m4 | ||
| autogen.sh | ||
| configure.ac | ||
| xcb-composite.pc.in | ||
| xcb-damage.pc.in | ||
| xcb-dpms.pc.in | ||
| xcb-glx.pc.in | ||
| xcb-randr.pc.in | ||
| xcb-record.pc.in | ||
| xcb-render.pc.in | ||
| xcb-res.pc.in | ||
| xcb-screensaver.pc.in | ||
| xcb-shape.pc.in | ||
| xcb-shm.pc.in | ||
| xcb-sync.pc.in | ||
| xcb-xevie.pc.in | ||
| xcb-xf86dri.pc.in | ||
| xcb-xfixes.pc.in | ||
| xcb-xinerama.pc.in | ||
| xcb-xlib.pc.in | ||
| xcb-xprint.pc.in | ||
| xcb-xtest.pc.in | ||
| xcb-xv.pc.in | ||
| xcb-xvmc.pc.in | ||
| xcb.pc.in | ||
About libxcb
============
libxcb provides an interface to the X Window System protocol, which replaces
the current Xlib interface. It has several advantages over Xlib, including:
- size: small library and lower memory footprint
- latency hiding: batch several requests and wait for the replies later
- direct protocol access: one-to-one mapping between interface and protocol
- proven thread support: transparently access XCB from multiple threads
- easy extension implementation: interfaces auto-generated from XML-XCB
Xlib can also use XCB as a transport layer, allowing software to make
requests and receive responses with both, which eases porting to XCB.
However, client programs, libraries, and toolkits will gain the most
benefit from a native XCB port.
Please report any issues you find to the freedesktop.org bug tracker,
at:
<https://bugs.freedesktop.org/enter_bug.cgi?product=XCB>
Discussion about XCB occurs on the XCB mailing list:
<mailto:xcb at lists.freedesktop.org>
<http://lists.freedesktop.org/mailman/listinfo/xcb>
You can obtain the latest development versions of XCB using GIT.
For anonymous checkouts, use:
git clone git://anongit.freedesktop.org/git/xcb/libxcb
For developers, use:
git clone git+ssh://git.freedesktop.org/git/xcb/libxcb