Re: kern/39420: stopped processes can hold locks

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/39420; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, kern-bug-people%netbsd.org@localhost,
        gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/39420: stopped processes can hold locks
Date: Sat, 11 Oct 2008 23:11:48 +0000

 On Thu, Oct 02, 2008 at 08:12:35AM +0900, YAMAMOTO Takashi wrote:
  > > >Number:         39420
  > > >Category:       kern
  > > >Synopsis:       stopped processes can hold locks
  > 
  > are you using interruptible nfs mount?
  > in that case, nfs uses PCATCH/cv_wait_sig for I/O and can be
  > suspended by user.
 
 Yes.
 
  > ups@ suggested introducing something like PCATCH|PNOSUSPEND while ago.
  > i think that an alternative is not suspending LWPs in the middle of
  > sleepq_block.  ie. suspend LWPs only on user-kernel boundaries.
 
 I think that's a much better alternative. I don't think it's safe to
 suspend anything except at the user-kernel boundary. It's easy enough
 to use EINTR/ERESTARTSYS to get the LWPs there when necessary.
 
 When I looked into this before it appeared like it would require
 nontrivial changes, but I think I was probably missing something.
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost