linux-kernel - Re: [PATCH v2] kdump: Add udev events for memory online/offline

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Message-ID: <j9pusg$hr5$2@dough.gmane.org>
Date:	Mon, 14 Nov 2011 02:37:06 +0000 (UTC)
From:	WANG Cong <xiyou.wangcong@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	kexec@...ts.infradead.org
Subject: Re: [PATCH v2] kdump: Add udev events for memory online/offline

On Mon, 31 Oct 2011 14:21:46 +0100, Michael Holzheu wrote:

> On Fri, 2011-10-28 at 15:46 -0700, Andrew Morton wrote:
>> On Thu, 27 Oct 2011 11:32:45 +0200
> 
> [snip]
> 
>> I think a safer place from which to send the uevent is
>> memory_block_change_state() or even memory_block_action().  Because if
>> either of those functions later gets new callers, those callers might
>> forget to send the uevent?
> 
> Ok fine. I put the code into memory_block_change_state(). This also has
> the advantage that we are serialized by "mem->state_mutex". Not sure if
> we need that, but for CPU hotplug the udev events are also serialized
> with a lock. See  "drivers/base/cpu.c" -> cpu_hotplug_driver_lock()
> 
> Do you think the following patch is acceptable? 


Yes.

> ---
> From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> 
> Currently no udev events for memory hotplug "online" and "offline" are
> generated:
> 
> # udevadm monitor
> # echo offline > /sys/devices/system/memory/memory4/state ==> No event
> 
> When kdump is loaded, kexec detects the current memory configuration and
> stores it in the pre-allocated ELF core header. Therefore, for kdump it
> is necessary to reload the kdump kernel with kexec when the memory
> configuration changes (e.g. for online/offline hotplug memory).
> 
> In order to do this automatically, udev rules should be used. This
> kernel patch adds udev events for "online" and "offline". Together with
> this kernel patch, the following udev rules for online/offline have to
> be added to "/etc/udev/rules.d/98-kexec.rules":
> 
> SUBSYSTEM=="memory", ACTION=="online", PROGRAM="/etc/init.d/kdump
> restart" SUBSYSTEM=="memory", ACTION=="offline",
> PROGRAM="/etc/init.d/kdump restart"
> 
> Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>


Acked-by: WANG Cong <xiyou.wangcong@...il.com>

Thanks.

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