Petteri Räty - Latest comments on Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* http://blogs.gentoo.org/betelgeuse?disp=comments en-US http://backend.userland.com/rss 60 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Wed, 16 Apr 2008 23:49:27 +0000 Hedley Robertson [Visitor] c19805@http://blogs.gentoo.org/ Running Java on Linux has been the most frustrating experience I have had since I switched over from using Windows full time. <br /> <br /> Thanks for this workaround, this solved a ton of issues for me.<br /> <br /> This thread: http://forums.gentoo.org/viewtopic-p-4547777.html?sid=5877773e911fcf3de235b3c31414ad26<br /> <br /> Has a handy little java program you can compile and run in order to test the bugfix.
Thanks for this workaround, this solved a ton of issues for me.

This thread: http://forums.gentoo.org/viewtopic-p-4547777.html?sid=5877773e911fcf3de235b3c31414ad26

Has a handy little java program you can compile and run in order to test the bugfix.]]> http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c19805 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Tue, 30 Oct 2007 10:13:31 +0000 David [Visitor] c19255@http://blogs.gentoo.org/ WOW! Gotta say that fixed my java problems, Thanks!!!!!! http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c19255 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Wed, 05 Sep 2007 14:25:39 +0000 Rob [Visitor] c19044@http://blogs.gentoo.org/ You're genius my friend. This solution solved my problem with some java apps. http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c19044 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Sun, 19 Aug 2007 22:02:44 +0000 Stephan Sokolow [Visitor] c19024@http://blogs.gentoo.org/ Actually, it is a Java bug. That patch just disables XCB's equivalent to segfaulting on a double-free.<br /> <br /> See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6532373<br /> <br /> The gist of it is:<br /> 1. Java (including 1.6) is statically linked against a VERY old libXext compiled with threading off.<br /> 2. Java dynamically links against the modern libX11 with threading enabled and, when using the XCB version, XML-parser-like strictness.<br /> 3. If Java detects the Xinerama X extension, it does some calls to figure out how the Xinerama desktop is put together... which causees the problem.<br /> 4. The problem exists because the un-threaded libXext doesn't bother to acquire the lock but the XCB-backed threaded Xlib is then asked to release the lock and cries foul over it's equivalent of a double-free.<br /> <br /> To patch away XCB's strictness is like patching away XML's strictness or telling the Linux kernel to not throw segfaults if one program messes with another program's memory. You're just asking for trouble in the long run.<br /> <br /> According to that bug page, one of the Java people is working on solving the problem but, until they do, I'd suggest the following solution which someone on the bug page suggested instead:<br /> <br /> Run this sed line (adapt the path, obviously) so that Java doesn't detect Xinerama and doesn't call the problem code:<br /> sed -i 's/XINERAMA/FAKEEXTN/g' /opt/sun-jdk-1.6.0.02/jre/lib/amd64/xawt/libmawt.so<br />
See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6532373

The gist of it is:
1. Java (including 1.6) is statically linked against a VERY old libXext compiled with threading off.
2. Java dynamically links against the modern libX11 with threading enabled and, when using the XCB version, XML-parser-like strictness.
3. If Java detects the Xinerama X extension, it does some calls to figure out how the Xinerama desktop is put together... which causees the problem.
4. The problem exists because the un-threaded libXext doesn't bother to acquire the lock but the XCB-backed threaded Xlib is then asked to release the lock and cries foul over it's equivalent of a double-free.

To patch away XCB's strictness is like patching away XML's strictness or telling the Linux kernel to not throw segfaults if one program messes with another program's memory. You're just asking for trouble in the long run.

According to that bug page, one of the Java people is working on solving the problem but, until they do, I'd suggest the following solution which someone on the bug page suggested instead:

Run this sed line (adapt the path, obviously) so that Java doesn't detect Xinerama and doesn't call the problem code:
sed -i 's/XINERAMA/FAKEEXTN/g' /opt/sun-jdk-1.6.0.02/jre/lib/amd64/xawt/libmawt.so
]]> http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c19024 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Wed, 15 Aug 2007 15:55:01 +0000 Todd Partridge [Visitor] c19009@http://blogs.gentoo.org/ What does the xcb USE flag do? I see it mentioned now with the use of compiz-fusion. http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c19009 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Tue, 28 Nov 2006 07:00:58 +0000 betelgeuse [Member] c18473@http://blogs.gentoo.org/ I have tried 1.6 and it did not work either. http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c18473 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Tue, 28 Nov 2006 03:59:28 +0000 Brian [Visitor] c18471@http://blogs.gentoo.org/ Apparently this patch 'solves' that problem:<br /> http://cvs.archlinux.org/cgi-bin/viewcvs.cgi/x11-libs/libxcb/xcb_xlib-no-assert-on-lock.patch<br /> <br /> I'm not sure how safe or correct it is, but it allows broken apps to run. http://cvs.archlinux.org/cgi-bin/viewcvs.cgi/x11-libs/libxcb/xcb_xlib-no-assert-on-lock.patch

I'm not sure how safe or correct it is, but it allows broken apps to run.]]> http://blogs.gentoo.org/betelgeuse/2006/11/26/do_not_turn_on_the_xcb_use_flag_if_you_p_5#c18471 In response to: Do not turn on the xcb use flag if you plan on using =sun-jre-1.5* Mon, 27 Nov 2006 07:16:46 +0000 Jamey Sharp [Visitor] c18469@http://blogs.gentoo.org/ <p>This was a bug in the open-source libXi library, which has been fixed upstream.</p> <p>Proprietary software considered harmful, certainly, but not actually the source of the problem this time. :-)</p> This was a bug in the open-source libXi library, which has been fixed upstream.

Proprietary software considered harmful, certainly, but not actually the source of the problem this time. :-)

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