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

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Date:   Tue, 12 Sep 2023 13:28:13 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dave Chinner <david@...morbit.com>,
        Waiman Long <longman@...hat.com>,
        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 11:03:42AM +0200, Peter Zijlstra wrote:
> 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 :-(

Are these actually abuse?  I looked at these two, and they both seem to
be asking "Does somebody else currently have this mutex?" rather than
"Do I have this mutex?".