Many /proc/PID files do not return the appropriate errors for exited tasks.

By "exited", I mean killed and waited on.

Many /proc/PID files aren't tested at all for zombied (killed but not waited on) or exited tasks, but should be. Not just to check for error values, but also because these files usually depend on Task state, which is often in a partially destroyed state for zombied and exited tasks. In the past, we've had proc files that would panic the sentry if read in this state.