Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Jules Irenge <jbi.octave@gmail.com>
Date:   Thu, 12 Mar 2020 09:56:01 +0000 (GMT)
To:     Andrew Morton <akpm@linux-foundation.org>
cc:     Matthew Wilcox <willy@infradead.org>,
        Jules Irenge <jbi.octave@gmail.com>, boqun.feng@gmail.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] backing-dev: refactor wb_congested_put()
In-Reply-To: <20200311200023.974009d9a5648b977d5168f6@linux-foundation.org>
Message-ID: <alpine.LFD.2.21.2003120953520.15830@ninjahub.org>
References: <20200312002156.49023-1-jbi.octave@gmail.com> <20200312002156.49023-2-jbi.octave@gmail.com> <20200311175919.30523d55b2e5307ba22bbdc0@linux-foundation.org> <20200312022948.GH22433@bombadil.infradead.org>
 <20200311200023.974009d9a5648b977d5168f6@linux-foundation.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On Wed, 11 Mar 2020, Andrew Morton wrote:

> On Wed, 11 Mar 2020 19:29:48 -0700 Matthew Wilcox <willy@infradead.org> wrote:
> 
> > On Wed, Mar 11, 2020 at 05:59:19PM -0700, Andrew Morton wrote:
> > > hm, it's hard to get excited over this.  Open-coding the
> > > refcount_dec_and_lock_irqsave() internals at a callsite in order to
> > > make sparse happy.
> > > 
> > > Is there some other way, using __acquires (for example)?
> > 
> > sparse is really bad at conditional lock acquisition. 
> 
> I can well imagine.
> 
> > we have similar
> > problems over the vfs.  but we shouldn't be obfuscating our code to make
> > the tool happy.
> 
> Perhaps sparse needs a way of being directed to suppress checking
> across a particular function.
> 
> 
Thanks for the feedback, maybe this is a limitation for Sparse.

I have experienced quite often this problem.