[PATCH] tile: avoid recursive backtrace faults

This change adds support for avoiding recursive backtracer crashes; we haven't seen this in practice other than when things are seriously corrupt, but it may help avoid losing the root cause of a crash. Also, don't abort kernel backtracers for invalid userspace PC's. If we do, we lose the ability

[PATCH] tile: avoid recursive backtrace faults

This change adds support for avoiding recursive backtracer crashes; we haven't seen this in practice other than when things are seriously corrupt, but it may help avoid losing the root cause of a crash. Also, don't abort kernel backtracers for invalid userspace PC's. If we do, we lose the ability