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Tue, 19 May 2020 06:06:21 -0700 (PDT) Received: from google.com ([2620:15c:2cd:202:2523:d194:de3b:636f]) by smtp.gmail.com with ESMTPSA id gd1sm2299753pjb.14.2020.05.19.06.06.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2020 06:06:17 -0700 (PDT) Date: Tue, 19 May 2020 06:06:14 -0700 From: Michel Lespinasse To: Vlastimil Babka Cc: Matthew Wilcox , Andrew Morton , linux-mm , LKML , Peter Zijlstra , Laurent Dufour , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Jason Gunthorpe , Daniel Jordan Subject: Re: [PATCH v5.5 09/10] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked() Message-ID: <20200519130614.GC189720@google.com> References: <20200422001422.232330-1-walken@google.com> <20200422001422.232330-11-walken@google.com> <20200422015829.GR5820@bombadil.infradead.org> <20200423015917.GA13910@bombadil.infradead.org> <20200424012612.GA158937@google.com> <20200424013858.GB158937@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, May 18, 2020 at 01:01:33PM +0200, Vlastimil Babka wrote: > On 4/24/20 3:38 AM, Michel Lespinasse wrote: > > +static inline void mmap_assert_locked(struct mm_struct *mm) > > +{ > > + VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_sem, -1), mm); > > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); > > +} > > + > > +static inline void mmap_assert_write_locked(struct mm_struct *mm) > > +{ > > + VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_sem, 0), mm); > > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); > > +} > > I would remove VM_BUG_ON_MM() from the lockdep part. If kernel has lockdep > enabled, it's already in heavy debugging mode enough so let's just use it and > not depend on DEBUG_VM. Many sites you convert don't require DEBUG_VM for the > lockdep checks. > > With that you can also use the standard lockdep_assert_held() and > lockdep_assert_held_write() wrappers. > > If user has both lockdep and DEBUG_VM enabled, should we run both variants? > Perhaps lockdep is enough as it's more comprehensive? Your initial v5 version > was doing that. Thanks, changed these to lockdep_assert_held() / lockdep_assert_held_write() as suggested. This misses dumping out the mm, but I think there is only limited value in that. I did keep the rwsem_is_locked fallback as people had commented earlier about getting assertions in the non-lockdep case. If both are enabled... then we'll get somewhat redundant assertions, but I think that is fine (better to keep the code simple than try to work around that). -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.