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Re: kern/39420: stopped processes can hold locks
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,
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.
> 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
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