Re: kern/52858: kernel lock up

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

The following reply was made to PR kern/52858; it has been noted by GNATS.

From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
To: "gnats-bugs%NetBSD.org@localhost" <gnats-bugs%netbsd.org@localhost>
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/52858: kernel lock up
Date: Tue, 26 Dec 2017 18:12:10 +0900

 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