Comment 3 for bug 823902

If you roll back to commit 2b41f10e186ccb4f0058815161586f8d6d006ea3 what is the pass/fail rate? That ought to separate out new bugs caused by recent commits (including the 0d101 change which is definitely wrong since it assumes cpu_single_env is only being used by one thread) from random other multithreaded-user-mode problems like 668799.

volatile ought to work and be a conservative fix (although I'm not a fan of volatile and compilers notoriously can't get it right). Making cpu_single_env thread-local sounds like a reasonable idea for user-mode, but I think that the current iothread code assumes that there is only one running CPU and cpu_single_env is how you get at it from the iothread. So if we go in that direction it would require more analysis of code to figure out what it's doing with cpu_single_env.