From: Jeff Dike <jdike@addtoit.com>
To: Adam Heath <doogie@brainfood.com>
Cc: user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] uml, ptrace, and BKL
Date: Sat, 18 Sep 2004 16:50:24 -0400 [thread overview]
Message-ID: <20040918205024.GA3748@ccure.user-mode-linux.org> (raw)
In-Reply-To: <Pine.LNX.4.58.0409181318020.1171@gradall.private.brainfood.com>
On Sat, Sep 18, 2004 at 01:20:39PM -0500, Adam Heath wrote:
> This is true(and something I hadn't considered). But with preemption, it's
> possible for multiple threads to be running in the kernel(as I understand it).
That's true in any case. The difference with preemption is that a thread
can be preempted involuntarily when it's in the kernel. This doesn't really
change anything with locking, especially the BKL. That's automatically dropped
when a thread calls schedule(), so that if a thread was preempted while
holding the BKL, it will drop it during the context switch.
> Same for a preemptible box.
Again, lock contention only really becomes an issue with lots of processors.
So, you may see some contention on a 2P box, but in order for it to be a
real problem, you'll probably need a lot more.
Jeff
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prev parent reply other threads:[~2004-09-18 19:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-18 0:23 [uml-devel] uml, ptrace, and BKL Adam Heath
2004-09-18 3:30 ` Jeff Dike
2004-09-18 2:30 ` Adam Heath
2004-09-18 13:18 ` Jeff Dike
2004-09-18 18:20 ` Adam Heath
2004-09-18 20:50 ` Jeff Dike [this message]
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