f0565e8f06
If a client calls close(2) on the connection's file descriptor and then
flushes writes, libxcb causes a hang in the client.
Any flush eventually calls _xcb_out_send() with has the following loop:
while(ret && *count)
ret = _xcb_conn_wait(c, &c->out.cond, vector, count);
_xcb_conn_wait(), if built with USE_POLL, gets the POLLNVAL error. It only
checks for POLLIN and POLLOUT though, ignoring the error. Return value is 1,
count is unmodified, leaving us with an endless loop and a client hang.
XTS testcase Xlib3/XConnectionNumber triggers this bug. It creates a display
connection, closes its file descriptor, tries to send a no-op, and then expects
an error.
http://cgit.freedesktop.org/xorg/test/xts/tree/xts5/Xlib3/XConnectionNumber.m
If poll returned POLLHUP or POLLERR, we might see the same result.
If poll returns any event we didn't ask for, this patch causes
_xcb_conn_shutdown() to be invoked and an error returned. This matches the
behaviour if select(2) is used instead of poll(2): select(2) returns -1 and
EBADF for an already closed file descriptor.
I believe this fix both is safe and will handle any similar error. POSIX says
that the only bits poll is permitted to set in revents are those bits that were
set in events, plus POLLHUP, POLLERR, and POLLNVAL. So if we see any flags we
didn't ask for then something has gone wrong.
Patch inspired by earlier proposals from Peter Hutterer and Aaron
Plattner--thanks!
Reported-by: Peter Hutterer <peter.hutterer@who-t.net>
Reported-by: Aaron Plattner <aplattner@nvidia.com>
Signed-off-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Tested-by: Aaron Plattner <aplattner@nvidia.com>
Cc: Peter Hutterer <peter.hutterer@who-t.net>
Cc: Dan Nicholson <dbn.lists@gmail.com>
Signed-off-by: Peter Harris <pharris@opentext.com>
|
||
|---|---|---|
| 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-dri2.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-xinput.pc.in | ||
| xcb-xprint.pc.in | ||
| xcb-xselinux.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, simple library, and lower memory footprint
- latency hiding: batch several requests and wait for the replies later
- direct protocol access: interface and protocol correspond exactly
- 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