On 02/26/2013 07:04 PM, Lai Jiangshan wrote:

On Tue, Feb 26, 2013 at 3:26 AM, Srivatsa S. Bhat
[off-list ref] wrote:

quoted

Hi Lai,

On 02/25/2013 09:23 PM, Lai Jiangshan wrote:

quoted

Hi, Srivatsa,

The target of the whole patchset is nice for me.

Cool! Thanks :-)

quoted

A question: How did you find out the such usages of
"preempt_disable()" and convert them? did all are converted?

Well, I scanned through the source tree for usages which implicitly
disabled CPU offline and converted them over.

How do you scan? could you show the way you scan the source tree.
I can follow your instructions for double checking.

Its nothing special. I grepped the source tree for anything dealing with
cpu_online_mask or its derivatives and also for functions/constructs that
rely on the cpumasks internally (eg: smp_call_function). Then I audited all
such call-sites and converted them (if needed) accordingly.

quoted

Its not limited to uses
of preempt_disable() alone - even spin_locks, rwlocks, local_irq_disable()
etc also help disable CPU offline. So I tried to dig out all such uses
and converted them. However, since the merge window is open, a lot of
new code is flowing into the tree. So I'll have to rescan the tree to
see if there are any more places to convert.

I remember some code has such assumption:
    preempt_disable() (or something else)
    //the code assume that the cpu_online_map can't be changed.
    preempt_enable()

It is very hard to find out all such kinds of assumptions and fixes them.
(I notice your code mainly fixes code around send_xxxx())

The conversion can be carried out using the method I mentioned above.

Regards,
Srivatsa S. Bhat