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From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	mingo@kernel.org, paulmck@linux.vnet.ibm.com,
	josh@joshtriplett.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] preempt/hardirq.h: Clarify PREEMPT_ACTIVE bit location
Date: Tue, 14 Aug 2012 08:46:34 -0400	[thread overview]
Message-ID: <1344948394.6724.3.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1208141216120.32033@ionos>

On Tue, 2012-08-14 at 12:18 +0200, Thomas Gleixner wrote:
> On Tue, 14 Aug 2012, Srivatsa S. Bhat wrote:
> 
> > 
> > By default, the PREEMPT_ACTIVE flag is bit 27, but different
> > architectures can override that. Update the comment to reflect
> > this fact.
> 
> Is there any sensible reason why architectures need to override that?
> I can't find one.
> 
> If there is none, then we should just remove all the overrides from
> the arch code instead. If there is a reason, then it should be
> documented.

IIRC, when I added the NMI bits to implement 'in_nmi()' I tried to make
this work across archs. But I found that bits in the preempt count have
been hard coded in assembly all over the place, and to clean it up
looked to be a nightmare.

It probably should be done, but I didn't have the time to do it then.
Perhaps we can revisit it.

In fact, looking at all the archs, I believe all archs override the
PREEMPT_ACTIVE bit, and not one of them uses the default (bit 27).

-- Steve



      reply	other threads:[~2012-08-14 12:46 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-20 19:24 [PATCH] preempt/hardirq.h: Fix comment about PREEMPT_ACTIVE bit location Srivatsa S. Bhat
2012-07-26 15:15 ` [tip:sched/urgent] sched: " tip-bot for Srivatsa S. Bhat
2012-07-31  3:49 ` [PATCH] preempt/hardirq.h: " Steven Rostedt
2012-08-14  8:26   ` Srivatsa S. Bhat
2012-08-14  8:28   ` [PATCH] preempt/hardirq.h: Clarify " Srivatsa S. Bhat
2012-08-14 10:18     ` Thomas Gleixner
2012-08-14 12:46       ` Steven Rostedt [this message]

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