From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Zach Brown <zach.brown@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
mingo@goodmis.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [HACK] convert i_alloc_sem for direct_io.c craziness!
Date: Mon, 01 Oct 2007 22:39:16 +0200 [thread overview]
Message-ID: <1191271156.5574.9.camel@lappy> (raw)
In-Reply-To: <20071001195256.GB7718@mami.zabbo.net>
On Mon, 2007-10-01 at 12:52 -0700, Zach Brown wrote:
> Do you have any suggestions for locking constructs that RT would prefer?
Basically, anything that maps to a simple mutex. Anything more complex
gets real messy real quick.
Locks that have non-exclusive states become non-deterministic because an
unbounded number of contexts can be in this state. Hence acquisition of
the exclusive state has unbounded time. Even when limited to a bounded
number, the ramifications to the PI graph will get you a head-ache.
Also, non-owner locks, ie. semaphores (asymetric acquisition vs release
contexts) are unusable because the lack of ownership undermines PI - who
to boost?
next prev parent reply other threads:[~2007-10-01 20:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-24 21:14 [HACK] convert i_alloc_sem for direct_io.c craziness! Steven Rostedt
2007-09-25 12:42 ` Peter Zijlstra
2007-09-25 15:29 ` [PATCH RT] Don't let -rt rw_semaphors do _non_owner locks Steven Rostedt
2007-10-01 19:52 ` [HACK] convert i_alloc_sem for direct_io.c craziness! Zach Brown
2007-10-01 20:39 ` Peter Zijlstra [this message]
2007-10-02 18:03 ` Zach Brown
2007-10-02 18:12 ` Steven Rostedt
2007-10-02 18:18 ` Zach Brown
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