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Subject: Re: [PATCH RT 1/2 v2] x86: Do not disable preemption in int3 on
 32bit
From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: linux-kernel@vger.kernel.org,
        linux-rt-users <linux-rt-users@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Carsten Emde <C.Emde@osadl.org>,
        John Kacur <jkacur@redhat.com>, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Alexander van Heukelum <heukelum@fastmail.fm>,
        Andi Kleen <ak@linux.intel.com>, Oleg Nesterov <oleg@redhat.com>,
        Clark Williams <williams@redhat.com>,
        Luis Goncalves <lgoncalv@redhat.com>
Date: Thu, 26 Jan 2012 08:33:31 -0500
In-Reply-To: <4F211126.1090204@hitachi.com>
References: <20120125143231.196670014@goodmis.org>
	 <20120125143520.086175333@goodmis.org> <4F211126.1090204@hitachi.com>
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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@goodmis.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