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authorKenneth Russel <[email protected]>2005-02-24 23:03:45 +0000
committerKenneth Russel <[email protected]>2005-02-24 23:03:45 +0000
commitc19545b4925ecc36bc8e637e0b4556731991bcd4 (patch)
tree85dd724628a6c529fa52569c868838563caaeaf2 /src/native/jogl
parent946c4c50fdcf6592af826f35f5e4dcedfbd93832 (diff)
Fixed Issue 109: Two animator threads on two Frames crash
Fixed Issue 124: SIGSEGV on Fedora Core 3 / NVIDIA Stability problems have been reported on all three of JOGL's major supported platforms (Windows, Linux and Mac OS X) whose root cause is multithreading-related bugs in vendors' OpenGL drivers. On Windows, the most recent version of NVidia's drivers (66.93) when run on a GeForce 6800 causes a blue screen of death upon exit from the simplest JOGL demo (Gears). On Linux, JVM crashes have been reported upon exit of certain test cases on NVidia hardware. The same test case causes a report of an unexpected async reply from Xlib on ATI hardware (at the last time of testing -- I no longer have access to a Linux machine with ATI hardware because all of their currently available drivers crash the X server on my machine). On Mac OS X, low-level warnings from Cocoa are printed in multithreaded JOGL situations which can lead to JVM crashes. All of these problems' root cause is that the current OpenGL drivers on the market, or supporting software built on them, were not designed to be used in a multithreaded fashion. Most C programs which use OpenGL are either single-threaded or perform all of their OpenGL work from a single thread. JOGL was originally designed to support OpenGL rendering from arbitrary threads and appropriate synchronization was introduced into the library to handle this. However, we have had to scale back this support as stability issues have been encountered. The most recent round of reported bugs, including the PC crash upon exit of the JOGL demos, is serious enough that we must take drastic measures. Support was introduced in earlier JOGL releases to move all of the OpenGL work performed by JOGL and users' code via the GLEventListener on to the AWT event dispatch thread. It turns out that doing this works around all of the above reported bugs. In JOGL 1.1 b08 and 1.1 b09, code changes were made to make this single-threaded support more correct; this checkin includes another small set of such changes, including some to the GLPbuffer implementation, and changes the default of the flag controlling this support to true. -Djogl.1thread=true is now the default. -Djogl.1thread=auto restores the behavior of previous releases, which was to enable the single-threaded mode only with ATI cards. This auto-detection mechanism was not robust enough and adding cases for the crashes above was not feasible. -Djogl.1thread=false disables the single-threaded workaround. Older synonyms for this system property, JOGL_SINGLE_THREADED_WORKAROUND and ATI_WORKAROUND, remain in the source base for the time being. Changing the value of any of these system properties is not recommended. The expected performance impact of these changes is minimal. In earlier JOGL releases it appeared that the overhead of making a context current and releasing it each frame was very significant and a key differentiator in being able to match C performance. More recent tests seem to indicate that this is no longer the case, at least with current hardware. Regardless, we must achieve stability in order for the library to be useful and this seems to be the best means of achieving that goal. We believe that the compatibility impact of these changes for existing JOGL applications will also be minimal. For correctly-written JOGL applications, the only visible change in behavior should be that the values of thread-local variables accessed through the java.lang.ThreadLocal class may change since the actual thread on which the GLEventListener's callbacks will be executed may have changed. Multithreaded JOGL applications performing complex inter-thread synchronization may see subtle differences in behavior. We hope that such applications and the developers writing them will be able to handle this change in behavior without much trouble. We will continue to work with graphics card vendors to improve the stability of their OpenGL drivers. Until that happens, we believe this change will yield the best possible improvement in stability and portability for applications using JOGL. git-svn-id: file:///usr/local/projects/SUN/JOGL/git-svn/svn-server-sync/jogl/trunk@241 232f8b59-042b-4e1e-8c03-345bb8c30851
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