From: davej@redhat.com (Dave Jones)
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Rudolf Marek <r.marek@assembler.cz>,
norsk5@xmission.com, lkml <linux-kernel@vger.kernel.org>,
LM Sensors <lm-sensors@lm-sensors.org>,
bluesmoke-devel@lists.sourceforge.net
Subject: [lm-sensors] [RFC] new MSR r/w functions per CPU
Date: Wed, 13 Dec 2006 22:26:16 +0000 [thread overview]
Message-ID: <20061213222616.GJ2418@redhat.com> (raw)
In-Reply-To: <45807C88.6060807@zytor.com>
On Wed, Dec 13, 2006 at 02:19:52PM -0800, H. Peter Anvin wrote:
> > void rdmsr_on_cpu(unsigned int cpu, unsigned long msr, unsigned long *lo, unsigned long *hi)
> > {
> > cpumask_t oldmask;
> >
> > oldmask = current->cpus_allowed;
> > set_cpus_allowed(current, cpumask_of_cpu(cpu));
> >
> > rdmsr(msr, &lo, &hi);
> >
> > set_cpus_allowed(current, oldmask);
> > }
> >
>
> [The above doesn't work, by the way. This approach was discussed a long
> time ago, and vetoed due to the potential for deadlock.]
Can you explain this a little further? I'm fairly certain
there are places in the kernel already doing this (or similar).
In fact, I cut-n-pasted most of the above from similar code in the
powernow-k8 driver. What exactly can we deadlock on?
Dave
--
http://www.codemonkey.org.uk
WARNING: multiple messages have this Message-ID (diff)
From: Dave Jones <davej@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Rudolf Marek <r.marek@assembler.cz>,
norsk5@xmission.com, lkml <linux-kernel@vger.kernel.org>,
LM Sensors <lm-sensors@lm-sensors.org>,
bluesmoke-devel@lists.sourceforge.net
Subject: Re: [RFC] new MSR r/w functions per CPU
Date: Wed, 13 Dec 2006 17:26:16 -0500 [thread overview]
Message-ID: <20061213222616.GJ2418@redhat.com> (raw)
In-Reply-To: <45807C88.6060807@zytor.com>
On Wed, Dec 13, 2006 at 02:19:52PM -0800, H. Peter Anvin wrote:
> > void rdmsr_on_cpu(unsigned int cpu, unsigned long msr, unsigned long *lo, unsigned long *hi)
> > {
> > cpumask_t oldmask;
> >
> > oldmask = current->cpus_allowed;
> > set_cpus_allowed(current, cpumask_of_cpu(cpu));
> >
> > rdmsr(msr, &lo, &hi);
> >
> > set_cpus_allowed(current, oldmask);
> > }
> >
>
> [The above doesn't work, by the way. This approach was discussed a long
> time ago, and vetoed due to the potential for deadlock.]
Can you explain this a little further? I'm fairly certain
there are places in the kernel already doing this (or similar).
In fact, I cut-n-pasted most of the above from similar code in the
powernow-k8 driver. What exactly can we deadlock on?
Dave
--
http://www.codemonkey.org.uk
next prev parent reply other threads:[~2006-12-13 22:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-13 21:45 [lm-sensors] [RFC] new MSR r/w functions per CPU Rudolf Marek
2006-12-13 21:45 ` Rudolf Marek
2006-12-13 22:01 ` [lm-sensors] " H. Peter Anvin
2006-12-13 22:01 ` H. Peter Anvin
2006-12-13 22:10 ` [lm-sensors] " Dave Jones
2006-12-13 22:10 ` Dave Jones
2006-12-13 22:19 ` [lm-sensors] " H. Peter Anvin
2006-12-13 22:19 ` H. Peter Anvin
2006-12-13 22:26 ` Dave Jones [this message]
2006-12-13 22:26 ` Dave Jones
2006-12-13 22:45 ` [lm-sensors] " H. Peter Anvin
2006-12-13 22:45 ` H. Peter Anvin
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