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[142.68.57.212]) by smtp.gmail.com with ESMTPSA id 68sm1880572qkh.75.2020.03.26.10.56.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 26 Mar 2020 10:56:44 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jHWkG-0002Yj-45; Thu, 26 Mar 2020 14:56:44 -0300 Date: Thu, 26 Mar 2020 14:56:44 -0300 From: Jason Gunthorpe To: Michel Lespinasse Cc: Andrew Morton , linux-mm , LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Matthew Wilcox , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han Subject: Re: [PATCH 1/8] mmap locking API: initial implementation as rwsem wrappers Message-ID: <20200326175644.GN20941@ziepe.ca> References: <20200326070236.235835-1-walken@google.com> <20200326070236.235835-2-walken@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200326070236.235835-2-walken@google.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 26, 2020 at 12:02:29AM -0700, Michel Lespinasse wrote: > +static inline bool mmap_is_locked(struct mm_struct *mm) > +{ > + return rwsem_is_locked(&mm->mmap_sem) != 0; > +} I've been wondering if the various VM_BUG(rwsem_is_locked()) would be better as lockdep expressions? Certainly when lockdep is enabled it should be preferred, IMHO. So, I think if inlines are to be introduced this should be something similar to netdev's ASSERT_RTNL which seems to have worked well. Maybe ASSERT_MMAP_SEM_READ/WRITE/HELD() and do the VM_BUG or lockdep_is_held as appropriate? Jason