Messages in this thread | | | Date | 22 Sep 2005 11:48:18 +0200 | Date | Thu, 22 Sep 2005 11:48:18 +0200 | From | Andi Kleen <> | Subject | Re: init and zap low address mappings on demand for cpu hotplug |
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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.
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