Re: [dm-devel] [PATCH] Remove the spinlock protecting the pages allocation

[Mikulas Patocka <mpatocka redhat com>]

On Mon, 23 May 2011, Joe Thornber wrote:

> On Thu, 2011-05-19 at 12:58 -0400, Mikulas Patocka wrote:
> > The spinlock is only taken on initialization or from single-threaded
> > workqueue.
> > Therefore, the spinlock is useless. 
> 
> The spinlock has memory barrier semantics as well.  How are you
> guaranteeing the changes from the initialisation thread are visible in
> the workqueue thread?

There is another spinlock, kc->job_lock, that is taken each time someone 
pushes or pops some work for the worker thread.

Once we take kc->job_lock, we guarantee that any written memory is 
visible to the other CPUs.

Mikulas

> - Joe
> 
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