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Date: Tue, 6 Jul 2004 17:17:32 +1000
From: Tim Robbins <tjr@freebsd.org>
To: ngl <ngl@ur.ru>
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cc: freebsd-stable@freebsd.org
Subject: Re: Shared/exclusive (rw) locks
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On Tue, Jul 06, 2004 at 12:45:27PM +0600, ngl wrote:
> That means, freebsd stable has no spin rwlocks ?

Right. Reader-writer spinlocks would not be very useful in FreeBSD 4; because
only one thread can be running in the kernel at once, the only opportunity
you'd have to share reader locks would be if you slept while holding a
spinlock, which is a bad idea (and not permitted by FreeBSD 5 or Linux).
If you want -rwlocks, you'll have to use lockmgr() (which is a sleep lock).


Tim