linux-kernel - Re: [PATCH 1/4] blkcg: Drop unnecessary RCU read [un]locks from blkg_conf

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Message-ID: <20230110064900.GA10277@lst.de>
Date:   Tue, 10 Jan 2023 07:49:00 +0100
From:   Christoph Hellwig <hch@....de>
To:     Tejun Heo <tj@...nel.org>
Cc:     Christoph Hellwig <hch@....de>, axboe@...nel.dk,
        josef@...icpanda.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] blkcg: Drop unnecessary RCU read [un]locks from
 blkg_conf_prep/finish()

On Mon, Jan 09, 2023 at 10:48:55AM -1000, Tejun Heo wrote:
> Now that all RCU flavors have been combined, holding a spin lock, disabling
> irq, disabling preemption all imply RCU read lock.

Can you write it like this in the commit log, please? 

> I can drop the changes but this actually bothers me. The annotation has been
> broken for a *long* time and nobody noticed. Furthermore, I can't remember a
> time when __acquires/__releases notation caught anything that lockdep
> couldn't trivially and can't even think of a way how it could. AFAICS, these
> annotations don't contribute anything other than preservation of themselves.
> I don't see why we would want to keep them.

People have noticed it.  It just hasn't been a priority as there are
lots of even more problematic things.