linux-kernel - RE: [RFC][PATCH 2/7] kref: Add kref

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Date:   Thu, 17 Nov 2016 15:42:02 +0000
From:   "Reshetova, Elena" <elena.reshetova@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     David Windsor <dave@...gbits.org>,
        Kees Cook <keescook@...omium.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: RE: [RFC][PATCH 2/7] kref: Add kref_read()

> Even if we now find all occurrences of atomic_t used as refcounter 
> (which we cannot actually guarantee in any case unless someone 
> manually reads every line) and convert it to refcount_t, we still have 
> atomic_t type present and new usage of it as refount will crawl in. It 
> is just a matter of time IMO.

>Improve tooling. The patterns shouldn't be _that_ hard to find. Once the tools are good, new code isn't a problem either.

>Anything: atomic*_{{dec,sub}_and_test,{add,sub}_return,fetch_{add,sub}}
>followed by a call_rcu()/free().

Does not find everything unfortunately. Even if you add to above atomic*_add_unless() and also things like schedule_work(), still I fear we aren't covering everything. 
What is worse, I don't think there is a mechanism to guarantee full coverage.