linux-kernel - Re: [PATCH RT 1/2 v2] x86: Do not disable preemption in int3 on 32bit

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Message-ID: <1327587719.22710.95.camel@gandalf.stny.rr.com>
Date:	Thu, 26 Jan 2012 09:21:59 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Carsten Emde <C.Emde@...dl.org>,
	John Kacur <jkacur@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Andi Kleen <ak@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Clark Williams <williams@...hat.com>,
	Luis Goncalves <lgoncalv@...hat.com>
Subject: Re: [PATCH RT 1/2 v2] x86: Do not disable preemption in int3 on
 32bit

On Thu, 2012-01-26 at 22:59 +0900, Masami Hiramatsu wrote:

> Better. If the functions are only for signaling, how
> about using the "signal" in name? :)
> 
> conditional_sti/cli_for_signal()

I don't think they are only for signals. The conditional_sti/cli is for
all callers of do_trap(). But those callers that run on an IST stack use
the preempt_conditional_sti/cli() code. Perhaps we should call it:

conditional_sti/cli_ist() ?

Actually, I think this is the best name. The "preempt_" one, didn't give
any annotation about why it was disabling preemption. It was done
because the stack is on the IST and we can not schedule out. Thus, if we
add the "_ist()" to it, not only does it annotate why this call is
special, but also allows x86_32, which does not have an IST, not to have
to disable preemption.

-- Steve

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