linux-kernel - Re: [PATCH] preempt/hardirq.h: Clarify PREEMPT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1344948394.6724.3.camel@gandalf.stny.rr.com>
Date:	Tue, 14 Aug 2012 08:46:34 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	mingo@...nel.org, paulmck@...ux.vnet.ibm.com,
	josh@...htriplett.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] preempt/hardirq.h: Clarify PREEMPT_ACTIVE bit location

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/