From: Andi Kleen <ak@muc.de>
To: Ashok Raj <ashok.raj@intel.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org,
suresh.b.siddha@intel.com, discuss@x86-64.org
Subject: Re: init and zap low address mappings on demand for cpu hotplug
Date: 22 Sep 2005 11:48:18 +0200
Date: Thu, 22 Sep 2005 11:48:18 +0200 [thread overview]
Message-ID: <20050922094818.GB79762@muc.de> (raw)
In-Reply-To: <20050921135731.B14439@unix-os.sc.intel.com>
On Wed, Sep 21, 2005 at 01:57:31PM -0700, Ashok Raj wrote:
> Hi,
>
> to simplyfy cpu hotplug we didnt zap low mem address since we would require
> them post boot to bringup a new cpu. This caused bad effects when
> Suresh was testing some new code. More below.
This seems racy - how do you prevent udev running on another
CPU while another CPU boots? I suspect you need additional locks
to plug this race. Or use a fresh mm cloned from init_mm mm to do the
CPU bootup.
I don't like zap_low_first_time - it shouldn't be needed. In general
people have been complaining on i386 and x86-64 that we don't
unmap NULL early, so we don't catch bugs that happen on other
architectures.
Using a fresh mm for smp bootup would solve this nicely - one could
zap init_mm really early after entering from head.S and then
only ever undo it in private mms for smp bootup.
-Andi
next prev parent reply other threads:[~2005-09-22 9:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-21 20:57 init and zap low address mappings on demand for cpu hotplug Ashok Raj
2005-09-21 21:11 ` Andrew Morton
2005-09-21 22:39 ` Ashok Raj
2005-09-22 9:48 ` Andi Kleen [this message]
2005-09-24 0:28 ` Siddha, Suresh B
2005-09-26 6:58 ` Andi Kleen
2005-09-26 23:19 ` Siddha, Suresh B
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