On Thu, Oct 05, 2017 at 05:49:43AM +0900, Tetsuo Handa wrote: > On 2017/10/05 3:59, Johannes Weiner wrote: > > But the justification to make that vmalloc() call fail like this isn't > > convincing, either. The patch mentions an OOM victim exhausting the > > memory reserves and thus deadlocking the machine. But the OOM killer > > is only one, improbable source of fatal signals. It doesn't make sense > > to fail allocations preemptively with plenty of memory in most cases. > > By the time the current thread reaches do_exit(), > fatal_signal_pending(current) > should become false. As far as I can guess, the source of fatal signal will be > tty_signal_session_leader(tty, exit_session) which is called just before > tty_ldisc_hangup(tty, cons_filp != NULL) rather than the OOM killer. I don't > know whether it is possible to make fatal_signal_pending(current) true inside > do_exit() though...
It's definitely not the OOM killer, the memory situation looks fine when this happens. I didn't look closer where the signal comes from. That said, we trigger this issue fairly easily. We tested the revert over night on a couple thousand machines, and it fixed the issue (whereas the control group still saw the crashes).
