linux-kernel - Re: [ANNOUNCE] 3.2.9-rt17

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Date:	Thu, 08 Mar 2012 21:08:23 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [ANNOUNCE] 3.2.9-rt17

On Thu, 2012-03-08 at 15:01 -0500, Steven Rostedt wrote:
> 
> What I was hinting at was that the spin_lock() can boost, but it could
> also fail if there was a deadlock detected, and it wouldn't cause the
> system to hang. 

Right, that's spin_deadlock() ;-) And you can in fact write
spin_trydeadlock() as:

int spin_trydeadlock(spinlock_t *lock)
{
	return spin_deadlock(lock) != -EDEADLK;
}

The advantage of introducing spin_trydeadlock() is that you can merge it
upstream (modulo naming) and the !RT code won't change at all.

IIRC tglx said there were more sites than just the dcache that did this
inverse lock order trylock game.

Seems we're agreeing more than disagreeing.. anyway, if you care to give
it a go.. worst that can happen is that you'll get as big a mess as tglx
got :-)
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