linux-kernel - Re: [PATCH RFC 00/33] Compile-time thread-safety checking

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Message-ID: <94fa4f05-929f-4be8-b2d1-0277826984b1@acm.org>
Date: Fri, 7 Feb 2025 09:46:34 -0800
From: Bart Van Assche <bvanassche@....org>
To: Peter Zijlstra <peterz@...radead.org>, Marco Elver <elver@...gle.com>
Cc: Will Deacon <will@...nel.org>, Christoph Hellwig <hch@....de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>,
 Nathan Chancellor <nathan@...nel.org>, Kees Cook <kees@...nel.org>,
 Jann Horn <jannh@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 00/33] Compile-time thread-safety checking

On 2/7/25 1:08 AM, Peter Zijlstra wrote:
> On Fri, Feb 07, 2025 at 10:05:47AM +0100, Marco Elver wrote:
>> Yes, you can add multiple guarded_by. But it's just going to enforce
>> that you need to hold both locks before you access the member. If you
>> want the rules to be more complex, the best way to express that is with
>> some helpers. E.g. something like this (tested on top my series)
> 
> Oh gawd, this is going to be a pain, isn't it :/

The Clang thread-safety annotations are used widely so behavior of
existing attributes must be preserved. I propose to introduce new
thread-safety attributes when useful to annotate kernel code. As an
example, the Clang try_acquire_capability function attribute does not
support functions that return pointers although this is a common pattern
in the Linux kernel. I think that introducing a new function attribute
to support functions that return pointers is a better solution than
trying to annotate such functions with any of the existing Clang
thread-safety attributes.

Thanks,

Bart.