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

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Message-ID: <1327584811.22710.80.camel@gandalf.stny.rr.com>
Date:	Thu, 26 Jan 2012 08:33:31 -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 17:39 +0900, Masami Hiramatsu wrote:
> (2012/01/25 23:32), Steven Rostedt wrote:
> > Preemption must be disabled before enabling interrupts in do_trap
> > on x86_64 because the stack in use for int3 and debug is a per CPU
> > stack set by th IST. But in 32bit, the stack still belongs to the
> > current task and there is no problem in scheduling out the task.
> > 
> > Keep preemption enabled on X86_32 when enabling interrupts for
> > do_trap().
> > 
> > Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> 
> Hmm, I think you'd better change caller side, because the
> function itself has "preempt" in its name. I think it can
> easily mislead other people.

How about if we rename it to

conditional_preempt_sti/cli() ?

Then it can be both a conditional preempt as well as interrupts being
disabled. The condition on preempt is "is 32 bits? don't preempt :
preempt";

-- Steve


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