From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.fraser@eu.citrix.com>
Subject: Re: [PATCH]CPUFREQ: Fix two racing issues during cpu
	hotplug
Date: Mon, 12 Apr 2010 07:59:36 +0100
Message-ID: <C7E88368.105A2%keir.fraser@eu.citrix.com>
References: <E6467867A6B05E4FA831B7DF29925F5C40F16BEE@shzsmsx502.ccr.corp.intel.com>
Mime-Version: 1.0
Content-Type: text/plain;
	charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <E6467867A6B05E4FA831B7DF29925F5C40F16BEE@shzsmsx502.ccr.corp.intel.com>
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: "Wei, Gang" <gang.wei@intel.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

On 12/04/2010 07:54, "Wei, Gang" <gang.wei@intel.com> wrote:

>> Can't you just kill_timer()? Adding extra code into a stop_machine
>> context is dangerous: e.g.,
>> xmalloc()->alloc_xenheap_pages()->memguard_unguard_range()->map_pages_to_xen
>> ()->flush_area_all() results in deadlock as other cpus are spinning
>> with irqs disabled.
> 
> You are right. kill_timer stop timer and wait until timer handler end if this
> timer is current running. I can switch to it. BTW, I may need to re-init the
> killed timer before set_timer on it, right?

Yes, init_timer() must be called to be able to reuse a kill_timer()ed timer.

 -- Keir