Comment # 46 on bug 1028575 from Mircea Kitsune

Thought I'd also post another detail that might be useful, I'm not sure how
much it relates to the freeze but better be safe than sorry; I have the
following two environment variables added to my ~/.profile file, which
basically tell Mesa to post errors to a log file:

export MESA_DEBUG=1
export MESA_LOG_FILE=/home/mircea/.mesa_stderr

There's one reoccurring line which keeps getting printed in there. It's added
periodically with no side effects, but I imagine it could still have some
relation to the trigger of the freeze:

Mesa: User error: GL_INVALID_OPERATION in glTexSubImage2D(invalid texture
image)