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Thu, 17 Sep 2020 06:19:44 -0700 (PDT) Date: Thu, 17 Sep 2020 15:19:42 +0200 From: Daniel Vetter To: Thomas =?iso-8859-1?Q?Hellstr=F6m_=28Intel=29?= Message-ID: <20200917131942.GX438822@phenom.ffwll.local> Mail-Followup-To: Thomas =?iso-8859-1?Q?Hellstr=F6m_=28Intel=29?= , DRI Development , Intel Graphics Development , Daniel Vetter , Sumit Semwal , Christian =?iso-8859-1?Q?K=F6nig?= , "open list:DMA BUFFER SHARING FRAMEWORK" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Dave Chinner , Qian Cai , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Jason Gunthorpe , Linux MM , linux-rdma , Maarten Lankhorst References: <20200728135839.1035515-1-daniel.vetter@ffwll.ch> <38cbc4fb-3a88-47c4-2d6c-4d90f9be42e7@shipmail.org> <60f2b14f-8cef-f515-9cf5-bdbc02d9c63c@shipmail.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <60f2b14f-8cef-f515-9cf5-bdbc02d9c63c@shipmail.org> X-Operating-System: Linux phenom 5.7.0-1-amd64 Subject: Re: [Intel-gfx] [PATCH] dma-resv: lockdep-prime address_space->i_mmap_rwsem for dma-resv X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-xfs@vger.kernel.org, linux-rdma , Daniel Vetter , Intel Graphics Development , Dave Chinner , DRI Development , Sumit Semwal , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Linux MM , Jason Gunthorpe , Qian Cai , linux-fsdevel@vger.kernel.org, Daniel Vetter , Andrew Morton , Christian =?iso-8859-1?Q?K=F6nig?= , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Thu, Jul 30, 2020 at 06:45:14PM +0200, Thomas Hellstr=F6m (Intel) wrote: > = > On 7/30/20 3:17 PM, Daniel Vetter wrote: > > On Thu, Jul 30, 2020 at 2:17 PM Thomas Hellstr=F6m (Intel) > > wrote: > > > = > > > On 7/28/20 3:58 PM, Daniel Vetter wrote: > > > > GPU drivers need this in their shrinkers, to be able to throw out > > > > mmap'ed buffers. Note that we also need dma_resv_lock in shrinkers, > > > > but that loop is resolved by trylocking in shrinkers. > > > > = > > > > So full hierarchy is now (ignore some of the other branches we alre= ady > > > > have primed): > > > > = > > > > mmap_read_lock -> dma_resv -> shrinkers -> i_mmap_lock_write > > > > = > > > > I hope that's not inconsistent with anything mm or fs does, adding > > > > relevant people. > > > > = > > > Looks OK to me. The mapping_dirty_helpers run under the i_mmap_lock, = but > > > don't allocate any memory AFAICT. > > > = > > > Since huge page-table-entry splitting may happen under the i_mmap_lock > > > from unmap_mapping_range() it might be worth figuring out how new page > > > directory pages are allocated, though. > > ofc I'm not an mm expert at all, but I did try to scroll through all > > i_mmap_lock_write/read callers. Found the following: > > = > > - kernel/events/uprobes.c in build_map_info: > > = > > /* > > * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through > > * reclaim. This is optimistic, no harm done if it fails. > > */ > > = > > - I got lost in the hugetlb.c code and couldn't convince myself it's > > not allocating page directories at various levels with something else > > than GFP_KERNEL. > > = > > So looks like the recursion is clearly there and known, but the > > hugepage code is too complex and flying over my head. > > -Daniel > = > OK, so I inverted your annotation and ran a memory hog, and got the below > splat. So clearly your proposed reclaim->i_mmap_lock locking order is an > already established one. > = > So > = > Reviewed-by: Thomas Hellstr=F6m No one complaining that this is a terrible idea and two reviews from people who know stuff, so I went ahead and pushed this to drm-misc-next. Thanks for taking a look at this. -Daniel > = > 8<-----------------------------------------------------------------------= ---------------------- > = > [=A0 308.324654] WARNING: possible circular locking dependency detected > [=A0 308.324655] 5.8.0-rc2+ #16 Not tainted > [=A0 308.324656] ------------------------------------------------------ > [=A0 308.324657] kswapd0/98 is trying to acquire lock: > [=A0 308.324658] ffff92a16f758428 (&mapping->i_mmap_rwsem){++++}-{3:3}, a= t: > rmap_walk_file+0x1c0/0x2f0 > [=A0 308.324663] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 but task is already holding lo= ck: > [=A0 308.324664] ffffffffb0960240 (fs_reclaim){+.+.}-{0:0}, at: > __fs_reclaim_acquire+0x5/0x30 > [=A0 308.324666] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 which lock already depends on = the new lock. > = > [=A0 308.324667] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 the existing dependency chain = (in reverse order) is: > [=A0 308.324667] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 -> #1 (fs_reclaim){+.+.}-{0:0}: > [=A0 308.324670]=A0=A0=A0=A0=A0=A0=A0 fs_reclaim_acquire+0x34/0x40 > [=A0 308.324672]=A0=A0=A0=A0=A0=A0=A0 dma_resv_lockdep+0x186/0x224 > [=A0 308.324675]=A0=A0=A0=A0=A0=A0=A0 do_one_initcall+0x5d/0x2c0 > [=A0 308.324676]=A0=A0=A0=A0=A0=A0=A0 kernel_init_freeable+0x222/0x288 > [=A0 308.324678]=A0=A0=A0=A0=A0=A0=A0 kernel_init+0xa/0x107 > [=A0 308.324679]=A0=A0=A0=A0=A0=A0=A0 ret_from_fork+0x1f/0x30 > [=A0 308.324680] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 -> #0 (&mapping->i_mmap_rwsem)= {++++}-{3:3}: > [=A0 308.324682]=A0=A0=A0=A0=A0=A0=A0 __lock_acquire+0x119f/0x1fc0 > [=A0 308.324683]=A0=A0=A0=A0=A0=A0=A0 lock_acquire+0xa4/0x3b0 > [=A0 308.324685]=A0=A0=A0=A0=A0=A0=A0 down_read+0x2d/0x110 > [=A0 308.324686]=A0=A0=A0=A0=A0=A0=A0 rmap_walk_file+0x1c0/0x2f0 > [=A0 308.324687]=A0=A0=A0=A0=A0=A0=A0 page_referenced+0x133/0x150 > [=A0 308.324689]=A0=A0=A0=A0=A0=A0=A0 shrink_active_list+0x142/0x610 > [=A0 308.324690]=A0=A0=A0=A0=A0=A0=A0 balance_pgdat+0x229/0x620 > [=A0 308.324691]=A0=A0=A0=A0=A0=A0=A0 kswapd+0x200/0x470 > [=A0 308.324693]=A0=A0=A0=A0=A0=A0=A0 kthread+0x11f/0x140 > [=A0 308.324694]=A0=A0=A0=A0=A0=A0=A0 ret_from_fork+0x1f/0x30 > [=A0 308.324694] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 other info that might help us = debug this: > = > [=A0 308.324695]=A0 Possible unsafe locking scenario: > = > [=A0 308.324695]=A0=A0=A0=A0=A0=A0=A0 CPU0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0 CPU1 > [=A0 308.324696]=A0=A0=A0=A0=A0=A0=A0 ----=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0 ---- > [=A0 308.324696]=A0=A0 lock(fs_reclaim); > [=A0 308.324697] lock(&mapping->i_mmap_rwsem); > [=A0 308.324698]=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 lock(fs_reclaim); > [=A0 308.324699]=A0=A0 lock(&mapping->i_mmap_rwsem); > [=A0 308.324699] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 *** DEADLOCK *** > = > [=A0 308.324700] 1 lock held by kswapd0/98: > [=A0 308.324701]=A0 #0: ffffffffb0960240 (fs_reclaim){+.+.}-{0:0}, at: > __fs_reclaim_acquire+0x5/0x30 > [=A0 308.324702] > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 stack backtrace: > [=A0 308.324704] CPU: 1 PID: 98 Comm: kswapd0 Not tainted 5.8.0-rc2+ #16 > [=A0 308.324705] Hardware name: VMware, Inc. VMware Virtual Platform/440BX > Desktop Reference Platform, BIOS 6.00 07/29/2019 > [=A0 308.324706] Call Trace: > [=A0 308.324710]=A0 dump_stack+0x92/0xc8 > [=A0 308.324711]=A0 check_noncircular+0x12d/0x150 > [=A0 308.324713]=A0 __lock_acquire+0x119f/0x1fc0 > [=A0 308.324715]=A0 lock_acquire+0xa4/0x3b0 > [=A0 308.324716]=A0 ? rmap_walk_file+0x1c0/0x2f0 > [=A0 308.324717]=A0 ? __lock_acquire+0x394/0x1fc0 > [=A0 308.324719]=A0 down_read+0x2d/0x110 > [=A0 308.324720]=A0 ? rmap_walk_file+0x1c0/0x2f0 > [=A0 308.324721]=A0 rmap_walk_file+0x1c0/0x2f0 > [=A0 308.324722]=A0 page_referenced+0x133/0x150 > [=A0 308.324724]=A0 ? __page_set_anon_rmap+0x70/0x70 > [=A0 308.324725]=A0 ? page_get_anon_vma+0x190/0x190 > [=A0 308.324726]=A0 shrink_active_list+0x142/0x610 > [=A0 308.324728]=A0 balance_pgdat+0x229/0x620 > [=A0 308.324730]=A0 kswapd+0x200/0x470 > [=A0 308.324731]=A0 ? lockdep_hardirqs_on_prepare+0xf5/0x170 > [=A0 308.324733]=A0 ? finish_wait+0x80/0x80 > [=A0 308.324734]=A0 ? balance_pgdat+0x620/0x620 > [=A0 308.324736]=A0 kthread+0x11f/0x140 > [=A0 308.324737]=A0 ? kthread_create_worker_on_cpu+0x40/0x40 > [=A0 308.324739]=A0 ret_from_fork+0x1f/0x30 > = > = > = > > > /Thomas > > > = > > > = > > > = > > = -- = Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx