Channel exception error with NVIDIA card: Using stackshot

Posted by Pierre Igot in: Macintosh
August 21st, 2009 • 11:43 am

I am afraid that, now that the problem has come back on my Mac Pro, it’s decided to stay for a while. I had another system-wide freeze yesterday, and that time I was not even opening a new file in Preview or anything like that. I was just moving a message window around in Mail. Apparently, that was enough to cause a “GPU restart” or whatever this thing is.

This time, however, I was ready to go to the next phase in diagnosing. I used my other Mac Pro to log in remotely and confirm that, even though the UI was entirely frozen, the machine was still running, with all its processes ambling along as if nothing untoward was happening.

I then proceeded to run the stackshot command as per Apple’s recommendations:

sudo /usr/libexec/stackshot -it

A fellow sufferer confirmed to me that the weird “end of file reached” error messages mentioned in my previous post on this topic appears to actually be a normal part of the execution of this command. And indeed after I wrote that last post, when I went back to Library/Logs/, I did find the two logs that the command was supposed to have created.

I trashed those back then, because they were obtained when the machine was running normally, so that I would have a blank slate the next time the problem occurred.

And when it occurred yesterday, I was able to run the command successfully via ssh, and did indeed obtain two new log files called “stackshot.log” and “stackshot-syms.log.”

I then proceeded to prepare a new bug report for Apple with the supporting documentation. I decided to both submit a new report and attach the same information to the existing case file, because Apple had changed the status of the existing case file to “Closed” and I didn’t want my bug report to be ignored, especially now that I had the stackshot log files that they had been asking for.

I saved an up-to-date system profile from System Profiler, compressed it and attached it to the bug report. I then attached a Zip archive containing the two stackshot logs (after changing their permissions, which are root-level permissions by default) and the relevant excerpt from the system log, which, as per usual, contained a slew of “channel exception error” messages right at the time that the system freeze had happened.

Of course, I have no idea how to read the stackshot logs myself, but if any Betalogue readers are more proficient and interested in viewing them, they just need to drop me an e-mail and I will oblige.

Now the question is whether Apple will respond to any of this. The fellow sufferer I mentioned has had no success with his own bug reports. He has sent stackshot logs as well, but has received no response. So far Apple has responded to my bug reports on this particular problem, so I guess we will have to wait and see.

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