Re: kern/54759: vm.ubc_direct deadlock when read()/write() into mapping of itself

[Andrew Doran <ad%netbsd.org@localhost>]

The following reply was made to PR kern/54759; it has been noted by GNATS.

From: Andrew Doran <ad%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/54759: vm.ubc_direct deadlock when read()/write() into
 mapping of itself
Date: Wed, 15 Jan 2020 20:03:43 +0000

 I can see how to prevent the deadlock (which I will try to do).  There is
 another problem though.  This goes ape bouncing around on PG_BUSY for
 libc.so's pages when doing build.sh on my machine.  I will try a bandaid
 with wakeup_one() but I think it needs PG_BUSY to be a kind of reader/writer
 lock to (something we could also use elsewhere).
 
 Andrew