Subject: Re: [PATCH 10/10] cpu bulk removal interface
From: Shaohua Li <shaohua.li@intel.com>
To: Nathan Lynch <ntl@pobox.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Ashok Raj <ashok.raj@intel.com>,
       Andrew Morton <akpm@osdl.org>
In-Reply-To: <20060508063130.GB9344@localdomain>
References: <1147067158.2760.90.camel@sli10-desk.sh.intel.com>
	 <20060508063130.GB9344@localdomain>
Content-Type: text/plain
Date: Mon, 08 May 2006 15:43:41 +0800
Message-Id: <1147074221.2760.107.camel@sli10-desk.sh.intel.com>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2373
Lines: 73

On Mon, 2006-05-08 at 01:31 -0500, Nathan Lynch wrote:
> Shaohua Li wrote:
> > 
> > Interface for bulk cpu removal. It's /sys/devices/system/cpu/cpu_bulk_remove
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> > ---
> > 
> >  linux-2.6.17-rc3-root/drivers/base/cpu.c  |   47 +++++++++++++++++++++++++++++-
> >  linux-2.6.17-rc3-root/include/linux/cpu.h |    3 +
> >  2 files changed, 49 insertions(+), 1 deletion(-)
> > 
> > diff -puN drivers/base/cpu.c~bulk_cpu_remove_interface drivers/base/cpu.c
> > --- linux-2.6.17-rc3/drivers/base/cpu.c~bulk_cpu_remove_interface	2006-05-07 07:47:02.000000000 +0800
> > +++ linux-2.6.17-rc3-root/drivers/base/cpu.c	2006-05-07 09:29:54.000000000 +0800
> > @@ -76,6 +76,46 @@ static inline void register_cpu_control(
> >  }
> >  #endif /* CONFIG_HOTPLUG_CPU */
> >  
> > +#ifdef CONFIG_BULK_CPU_REMOVE
> > +static ssize_t cpu_bulk_remove_show(struct sysdev_class *c, char *buf)
> > +{
> > +	int len;
> > +
> > +	len = cpulist_scnprintf(buf, PAGE_SIZE-1, cpu_online_map);
> > +	len += sprintf(buf + len, "\n");
> > +	return len;
> > +}
> 
> This doesn't really seem meaningful.  I'd say the attribute could do
> without a show method.
Ok, I'll remove it.

> > +static ssize_t cpu_bulk_remove_store(struct sysdev_class *c,
> > +	const char *buf, size_t count)
> > +{
> > +	int err;
> > +	cpumask_t removed_cpus;
> > +
> > +	if ((err = lock_cpu_hotplug_interruptible() != 0))
> > +		return err;
> > +	err = cpulist_parse(buf, removed_cpus);
> > +	if (err) {
> > +		unlock_cpu_hotplug();
> > +		return err;
> > +	}
> > +
> > +	unlock_cpu_hotplug();
> > +	cpu_down_mask(removed_cpus);
> > +	return count;
> > +}
> 
> Shouldn't this make sure that we don't offline all cpus?
cpu_down_mask will check it.

> Why are you using lock_cpu_hotplug_interruptible instead of
> lock_cpu_hotplug?
> 
> Why is only the parsing of the cpumask buffer protected by the cpu
> hotplug lock?  Shouldn't cpu_down_mask be called with the lock held?
we actually don't need lock here. I'll remove it.

> Can cpu_down_mask fail, and if so, shouldn't we be reporting the
> error?
Makes sense.

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