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Known Exceed Issues

Exceed 8

Issue 8a: MIT-SHM implementation not thread safe

Symptoms:

• Multi-threaded MIT-SHM test crashes in FBXtest
• Multiple threads crash or lock up in VGLclient when running rrfakerut with the VGL Transport to a machine running vglclient -x and Exceed v8

Fix:

1. install
   hclshm.dll 9.0.0.1 (or later)
   xlib.dll 9.0.0.3 (or later)
   exceed.exe 8.0.0.28 (or later)
   Patches available only via Hummingbird support web site (not available in any official Exceed releases or service packs)
2. Current releases of VGL work around this issue by detecting the version of hclshm.dll, xlib.dll, and exceed.exe and disabling MIT-SHM drawing (at the expense of performance) if those files have not been patched

Potential Impact: Moderate

• Any potential instability was mitigated by the above fix, but VGLclient will perform much more slowly if the above patches are not installed

Issue 8b: GLX implementation not thread safe

Symptoms:

• Occasionally, a thread crashes in VGLclient when running rrfakerut with the VGL Transport to a machine running vglclient -gl and Exceed 3D v8

Fix:

1. install
   exceed.exe 8.0.0.28 (or later)
   Patch available only via Hummingbird support web site (not available in any official Exceed releases or service packs)

Potential Impact: Minimal

• If many applications are sharing the same VGLclient instance, and if a significant number of them are using stereo rendering or VGLclient was configured to use OpenGL drawing, then one application instance may fail
• Unlikely to happen in real-world usage scenarios

Exceed 9

Issue 9a: (same as Issue 8a)

Fix:

1. install
   hclshm.dll 9.0.0.1 (or later)
   xlib.dll 9.0.0.3 (or later)
   exceed.exe 9.0.0.9 (or later)
   exceed.exe can be patched via Hummingbird Update or by downloading the latest Exceed 9 service pack. Other patches available only via Hummingbird support web site (not available in any official Exceed releases or service packs)
2. Current releases of VGL work around this issue by detecting the version of hclshm.dll, xlib.dll, and exceed.exe and disabling MIT-SHM drawing (at the expense of performance) if those files have not been patched

Exceed 10

Issue 10a: BadLength error in XPutImage()

Symptoms:

• FBX write tests (non-SHM) fail in FBXtest with repeated BadLength errors. This occurs regardless of whether FBXtest is run locally on the client or remotely from the server
• VGLclient fails silently if the MIT-SHM extension is not enabled in Exceed

Fix:
None available

Workarounds:

1. If using only the VGL Transport, then simply make sure that the MIT-SHM extension is enabled in Exceed. VGLclient only uses XPutImage() (and thus only encounters this bug) if MIT-SHM is not enabled
2. If using the X11 Transport, then it is necessary to enable "Use 32 Bits Per Pixel For TrueColor" in the "X Server Protocol" applet of XConfig. Note that this will decrease the performance of the VGL Transport significantly

Potential Impact: High

• If the user follows the procedure in the VGL docs, then the VGL Transport will work correctly and optimally (but the X11 Transport will not work)
• If the user ignores the docs altogether and uses the default Exceed settings, then the VGL Transport will work correctly but slowly (and the X11 Transport will work)
• If the user follows some of the procedure (for instance, disabling 32-bit pixels but failing to enable MIT-SHM), then both the X11 Transport and the VGL Transport may not work

Exceed 11 (Exceed 2006)

Issue 11a: Xlib not fully thread safe

Symptoms:

• rrframeut deadlocks consistently, and the stack traces show that the deadlock is occurring because an Xlib call failed to return

Fix:
None available

Workaround:
None available

Potential Impact: Minimal

• This bug is not encountered when running the multi-threaded tests of rrfakerut using the VGL Transport with Exceed 2006 as a client. This suggests that, even under the most extreme circumstances, the bug will probably not be encountered when running VirtualGL

Exceed 12 (Exceed 2007)

Issue 12a: MIT-SHM implementation in Exceed 2007 30-35% slower than the MIT-SHM implementation in other versions of Exceed

Symptoms:

• SHM write tests in FBXtest perform 30-35% slower than with other Exceed versions
• VGL pipeline performs 8-10% slower than with other Exceed versions

Fix:
None available

Workaround:
None available

Potential Impact: Moderate

• Affects all customers who use Exceed 2007, but overall performance impact is not that noticeable

Exceed 13 (Exceed 2008)

Issue 13a: XShmAttach() generates BadAccess or BadValue errors

Symptoms:

• The SHM tests in FBXtest fail with repeated BadAccess errors
• rrframeut fails with a BadValue error reported in opcode X_ShmAttach
• VGLclient fails silently when the MIT-SHM extension is enabled in Exceed 2008

Fix:

• install
  xlib.dll v13.0.1.235 (or later)
  or the latest Connectivity 2008 service pack.

Workaround:

• Disable the MIT-SHM extension in Exceed (this will significantly reduce the performance of the VGL Transport)

Potential Impact: High

• If the user follows the procedure in the VGL docs on an unpatched version of Exceed 2008, then the VGL Transport will not work
• The only workaround has a severe impact on performance

Issue 13b: (same as Issue 11a, only more sporadic)

Fix:
None available