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From: Robert Watson <rwatson@FreeBSD.org>
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To: Kris Kennaway <kris@obsecurity.org>
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cc: cvs-src@FreeBSD.org
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Subject: Re: cvs commit: src/sys/nfsclient nfs_lock.c
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On Wed, 26 Mar 2003, Kris Kennaway wrote:

> Thanks, this sounds like it may fix non-blocking calls to open() on a
> NFS file, which would previously block. 

Well, it depends whether the open() had flags like O_SHLOCK or O_EXLOCK
set.  This will only affect cases where advisory locking primitives were
used by userspace applications, resulting in a call into the NFS locking
code.  Interestingly, this case would previously timeout with:

  foo: Resource temporarily unavailable

on -CURRENT, but not -STABLE, due to a deadlock work-around in the fifo
code.  Only when the work-around was removed did this case pop up--before
the diskless boot would pause occasionally waiting for fifos to time out,
but then continue. 

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories