linux-kernel - Re: [PATCH 1/5] locking: Add rwsem_is_write

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Message-ID: <20230912090342.GC35261@noisy.programming.kicks-ass.net>
Date:   Tue, 12 Sep 2023 11:03:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     Waiman Long <longman@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J . Wong" <djwong@...nel.org>, linux-xfs@...r.kernel.org
Subject: Re: [PATCH 1/5] locking: Add rwsem_is_write_locked()

On Tue, Sep 12, 2023 at 08:29:55AM +1000, Dave Chinner wrote:

> So, once again, we have mixed messages from the lock maintainers.
> One says "no, it might get abused", another says "I'm fine with
> that", and now we have a maintainer disagreement stalemate.

I didn't say no, I was trying to see if there's alternatives because the
is_locked pattern has a history of abuse.

If not, then sure we can do this; it's not like I managed to get rid of
muteX_is_locked() -- and I actually tried at some point :/

And just now I grepped for it, and look what I find:

drivers/hid/hid-nintendo.c:     if (unlikely(mutex_is_locked(&ctlr->output_mutex))) {
drivers/nvdimm/btt.c:           if (mutex_is_locked(&arena->err_lock)

And there's more :-(

Also, please just calm down already..