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Thu, 23 Apr 2020 18:44:54 -0700 (PDT) Received: from google.com ([2620:15c:2cd:202:2523:d194:de3b:636f]) by smtp.gmail.com with ESMTPSA id c3sm3864956pfa.160.2020.04.23.18.44.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Apr 2020 18:44:53 -0700 (PDT) Date: Thu, 23 Apr 2020 18:44:51 -0700 From: Michel Lespinasse To: Matthew Wilcox Cc: Andrew Morton , linux-mm , LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Jason Gunthorpe , Daniel Jordan Subject: Re: [PATCH v5 09/10] mmap locking API: add mmap_assert_locked Message-ID: <20200424014451.GD158937@google.com> References: <20200422001422.232330-1-walken@google.com> <20200422001422.232330-10-walken@google.com> <20200422021850.GS5820@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200422021850.GS5820@bombadil.infradead.org> 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 Tue, Apr 21, 2020 at 07:18:50PM -0700, Matthew Wilcox wrote: > On Tue, Apr 21, 2020 at 07:10:39PM -0700, Michel Lespinasse wrote: > > On Tue, Apr 21, 2020 at 5:14 PM Michel Lespinasse wrote: > > > +static inline void mmap_assert_locked(struct mm_struct *mm) > > > +{ > > > + if (IS_ENABLED(CONFIG_LOCKDEP) && debug_locks) > > > + VM_BUG_ON_MM(!lockdep_is_held(&mm->mmap_sem), mm); > > > + else > > > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); > > > +} > > > > Turns out this function definition does not work for !CONFIG_LOCKDEP > > as lockdep_is_held is not defined in that case. > > Oops, sorry. It only defines > > #define lockdep_is_held_type(l, r) (1) > #define lockdep_assert_held(l) do { (void)(l); } while (0) > #define lockdep_assert_held_write(l) do { (void)(l); } while (0) > #define lockdep_assert_held_read(l) do { (void)(l); } while (0) > #define lockdep_assert_held_once(l) do { (void)(l); } while (0) > > which seems like an oversight, but not one that you should be fixing. > > > The following should work instead: > > > > static inline void mmap_assert_locked(struct mm_struct *mm) > > { > > #ifdef CONFIG_LOCKDEP > > if (debug_locks) { > > VM_BUG_ON_MM(!lockdep_is_held(&mm->mmap_lock), mm); > > return; > > } > > #endif > > VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); > > } > > Yes, I agree. Sent an updated version of this (also integrating your feedback on patch 10/10) Please look for it under subject: [PATCH v5.5 09/10] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked() -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.