Re: Potential data race in dput and __d_lookup

[Al Viro]

On Thu, Nov 20, 2014 at 09:20:14PM +0400, Andrey Konovalov wrote:

> It seems that one thread increments 'dentry->d_lockref.count', while
> other does 'lockref_put_or_lock(&dentry->d_lockref)'  without any
> synchronization.
> 
> Could you confirm if this is a real race?

I can not.  Increment in __d_lookup() is under ->d_lockref.lock (aka
->d_lock) and lockref_put_or_lock() is atomic wrt that.
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