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Date:      Tue, 30 Jun 1998 21:42:06 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        hackers@FreeBSD.ORG
Cc:        mkn@emailbox.hdtv.lucent.com, freebsd-questions@FreeBSD.ORG
Subject:   Re: Unsupport calls
Message-ID:  <199806302142.OAA21104@usr02.primenet.com>
In-Reply-To: <19980630155609.W1880@freebie.lemis.com> from "Greg Lehey" at Jun 30, 98 03:56:09 pm

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> > fdatasync - no support in FreeBSD.  Maybe not a big deal.
> 
> Yes, I can't find it either, not even in the Solaris man pages.  What
> does it do?

It is a Linux-ism having to do with syncing out the file data and
not the file metadata.

The FreeBSD equivalent is fsync(), since you have no choice on the
metadata, since FreeBSD obeys the POSIX semantics (which require
metadata updates to occur).


> > lockf - no support in FreeBSD.  Have to implement our own using fcntl(2)
> 
> Correct.  Again, an improvement which should also work under Solaris.

This depends.  You can actually avoid the brain-damaged POSIX
semantics for "any close removes all locks" if a system support
lockf() as a system call.

> About the only serious one I can see is plock.  Maybe somebody else on
> the list can comment.

It is trivial to implement p/v semaphores using __asm__ to generate
single instruction spinlocks; since the VM/buffer cache is unified,
this will work on shared memory/mmap'ed files without needing a
special system call to guaranteee lock coherency.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.

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