Re: [PATCH (2.4)] atomic use count for proc_dir_entry

From: Dan Aloni (karrde@callisto.yi.org)
Date: Thu Nov 16 2000 - 16:31:00 EST

On Thu, 16 Nov 2000, Linus Torvalds wrote:

> On Thu, 16 Nov 2000, Dan Aloni wrote:
> >
> > Makes procfs use an atomic use count for dir entries, to avoid using
> > the Big kernel lock. Axboe says it looks ok.
>
> There's a race there. Look at what happens if de_put() races with
> remove_proc_entry(): we'd do free_proc_entry() twice. Not good.
>
> Leave the kernel lock for now.

Is this particular kernel lock helps anyway? We could have been half way
through remove_proc_entry(), line 569, for example, while in the same time
another thread enters de_put when the use count is 1 and frees the entry
while the other thread is locked just before dereferencing the entry.

So, maybe a spinlock could be used here? 

-- 
Dan Aloni 
dax@karrde.org

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