Re: kern/52858: kernel lock up

[Ryota Ozaki <ozaki-r%netbsd.org@localhost>]

On Mon, Dec 25, 2017 at 11:50 AM,  <coypu%sdf.org@localhost> wrote:
> The following reply was made to PR kern/52858; it has been noted by GNATS.
>
> From: coypu%sdf.org@localhost
> To: gnats-bugs%NetBSD.org@localhost
> Cc:
> Subject: Re: kern/52858: kernel lock up
> Date: Mon, 25 Dec 2017 02:45:10 +0000
>
>  It looks like we can spin forever in pool_catchup if we have PR_WAITOK
>  allocation sleeping followed by a PR_NOWAIT allocation.
>
>
>  Single CPU, no kpreemption arch
>
>  [lwp #1]
>     |
>  [  ??  ]
>     |
>  [pool_grow with PR_WAITOK
>  [set PR_GROWING
>  [allocation, decide to sleep
>     |
>    zzZzzZ                          [lwp #2]
>                                       |
>                                    [  ??  ]
>                                       |
>                                    [pool_catchup with PR_NOWAIT
>                                    [see PR_GROWING already set,
>                                    [spin forever returning ERESTART
>                                    [(nothing ever preempts me or
>                                    increases the pool items)
>

FYI: similar backtrace here (on amd64 though):
  http://mail-index.netbsd.org/source-changes-d/2017/12/26/msg009751.html

  ozaki-r