linux-kernel - Re: [patch 2.6.24-rc2 1/3] generic gpio -- gpio

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

Message-Id: <200711132325.53846.nickpiggin@yahoo.com.au>
Date:	Tue, 13 Nov 2007 23:25:53 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	David Brownell <david-b@...bell.net>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Florian Fainelli <florian.fainelli@...ecomint.eu>,
	Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: Re: [patch 2.6.24-rc2 1/3] generic gpio -- gpio_chip support

On Wednesday 14 November 2007 06:22, David Brownell wrote:
> On Tuesday 13 November 2007, Ingo Molnar wrote:
> > * David Brownell <david-b@...bell.net> wrote:
> > > > > I speculate that either the design has changed (without fanfare),
> > > > > or else that stuff is in RT kernels and has not yet gone upstream.
> > > >
> > > > Well whatever.  We shouldn't have to resort to caller-side party
> > > > tricks like this to get acceptable performance.
> > >
> > > I'd be happy if, as originally presented, it were possible to just
> > > pass a raw_spinlock_t to spin_lock_irqsave() and friends.
> >
> > that's a spinlock type abstraction of PREEMPT_RT, not of mainline.

Even when you're talking about the -rt tree, I suspect you really
shouldn't be using raw spinlocks, right? I mean, if you have a
timing critical operation, then you should ensure you have priorities
set correctly so that you simply don't get preempted.

By using a raw_spinlock_t, you're saying that you're more important
than anyone else (for the period of the critical section) including
processes which the user has explicitly set to a higher priority.

If you get preempted, then you should be happy, because <standard
RTOS nuclear power plant scenario> didn't occur.

> Any reason that stuff shouldn't move into mainline?

This sort of raw_spinlock_t arms race throughout drivers/ would be
a huge reason not to move it into mainline.
-
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/