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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a90f11a7c2sm932482e87.32.2026.05.14.21.05.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 May 2026 21:05:53 -0700 (PDT) Message-ID: <2fe8d022-a414-4b23-af4f-9cecf1aac3d1@redhat.com> Date: Fri, 15 May 2026 07:05:52 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 0/5] Migrate on fault for device pages To: Balbir Singh Cc: linux-mm@kvack.org, dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-kernel@vger.kernel.org, David Hildenbrand , Jason Gunthorpe , Leon Romanovsky , Alistair Popple , Zi Yan , Matthew Brost , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko References: <20260505184421.2324798-1-mpenttil@redhat.com> Content-Language: en-US From: =?UTF-8?Q?Mika_Penttil=C3=A4?= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, > FYI: While testing with hmm_tests I ran into > > [ 107.866004] ============================================ > [ 107.866284] WARNING: possible recursive locking detected > [ 107.866577] 7.1.0-rc3-00311-g4277273ca0e1 #12 Not tainted > [ 107.866877] -------------------------------------------- > [ 107.867217] hmm-tests/1098 is trying to acquire lock: > [ 107.867491] ffff888113571b38 (&mm->mmap_lock){++++}-{4:4}, at: dmirror_range_fault+0x147/0x610 [test_hmm] <- line 368 of lib/test_hmm.c > [ 107.868076] > [ 107.868076] but task is already holding lock: > [ 107.868383] ffff888113571b38 (&mm->mmap_lock){++++}-{4:4}, at: dmirror_fault_and_migrate_to_device.constprop.0+0x3aa/0x6a0 [test_hmm] <- line 1267 of lib/test_hmm.c > [ 107.869076] > [ 107.869076] other info that might help us debug this: > [ 107.869415] Possible unsafe locking scenario: > [ 107.869415] > [ 107.869729] CPU0 > [ 107.869866] ---- > [ 107.870054] lock(&mm->mmap_lock); > [ 107.870247] lock(&mm->mmap_lock); > [ 107.870436] > [ 107.870436] *** DEADLOCK *** > [ 107.870436] > [ 107.870743] May be due to missing lock nesting notation > [ 107.870743] > [ 107.871158] 1 lock held by hmm-tests/1098: > [ 107.871377] #0: ffff888113571b38 (&mm->mmap_lock){++++}-{4:4}, at: dmirror_fault_and_migrate_to_device.constprop.0+0x3aa/0x6a0 [test_hmm] > [ 107.872081] > [ 107.872081] stack backtrace: > [ 107.872348] CPU: 1 UID: 0 PID: 1098 Comm: hmm-tests Not tainted 7.1.0-rc3-00311-g4277273ca0e1 #12 PREEMPT(full) > [ 107.872350] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20260213-6.fc44 02/13/2026 > [ 107.872354] Call Trace: > [ 107.872357] > [ 107.872358] dump_stack_lvl+0x5d/0x80 > [ 107.872385] print_deadlock_bug.cold+0xc0/0xe2 > [ 107.872393] __lock_acquire+0x10cf/0x1b90 > [ 107.872400] lock_acquire+0x189/0x2f0 > [ 107.872401] ? dmirror_range_fault+0x147/0x610 [test_hmm] > [ 107.872404] down_read+0x9b/0x4b0 > [ 107.872420] ? dmirror_range_fault+0x147/0x610 [test_hmm] > [ 107.872421] ? lock_acquire+0x189/0x2f0 > [ 107.872422] ? __pfx_down_read+0x10/0x10 > [ 107.872424] ? __lock_acquire+0x3c2/0x1b90 > [ 107.872425] dmirror_range_fault+0x147/0x610 [test_hmm] > [ 107.872427] ? __pfx_down_read+0x10/0x10 > [ 107.872429] ? __pfx_dmirror_range_fault+0x10/0x10 [test_hmm] > [ 107.872430] ? __lock_acquire+0x3c2/0x1b90 > [ 107.872434] dmirror_fault_and_migrate_to_device.constprop.0+0x3bf/0x6a0 [test_hmm] > [ 107.872436] ? __pfx_dmirror_fault_and_migrate_to_device.constprop.0+0x10/0x10 [test_hmm] > [ 107.872439] ? find_held_lock+0x2b/0x80 > [ 107.872444] ? dmirror_device_remove_chunks+0x5b8/0xa00 [test_hmm] > [ 107.872445] ? __is_insn_slot_addr+0xee/0x1f0 > [ 107.872458] ? lock_acquire+0x189/0x2f0 > [ 107.872460] ? avc_has_extended_perms+0x234/0x1350 > [ 107.872476] ? __might_fault+0x89/0x150 > [ 107.872484] ? lock_release+0xe1/0x320 > [ 107.872486] dmirror_fops_unlocked_ioctl+0x9ba/0xdb0 [test_hmm] > [ 107.872488] ? ioctl_has_perm.constprop.0.isra.0+0x2fe/0x6c0 > [ 107.872494] ? __pfx_dmirror_fops_unlocked_ioctl+0x10/0x10 [test_hmm] > [ 107.872498] ? count_memcg_events_mm.constprop.0+0x22/0x1a0 > [ 107.872499] ? __pfx_ioctl_has_perm.constprop.0.isra.0+0x10/0x10 > [ 107.872501] ? count_memcg_events_mm.constprop.0+0xaa/0x1a0 > [ 107.872503] ? lock_release+0xe1/0x320 > [ 107.872504] ? find_held_lock+0x2b/0x80 > [ 107.872506] ? exc_page_fault+0x7e/0xf0 > [ 107.872510] __x64_sys_ioctl+0x13c/0x1d0 > [ 107.872521] ? lockdep_hardirqs_on_prepare+0xd9/0x190 > [ 107.872523] do_syscall_64+0xf3/0x6a0 > [ 107.872526] ? exc_page_fault+0xde/0xf0 > [ 107.872528] entry_SYSCALL_64_after_hwframe+0x77/0x7f > [ 107.872529] RIP: 0033:0x7f7381c543ad > [ 107.872531] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00 > [ 107.872532] RSP: 002b:00007ffc3160a9b0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > [ 107.872539] RAX: ffffffffffffffda RBX: 00007f7381b44000 RCX: 00007f7381c543ad > [ 107.872540] RDX: 00007ffc3160aa30 RSI: 00000000c0284803 RDI: 0000000000000022 > [ 107.872541] RBP: 00007ffc3160aa00 R08: 00000000ffffffff R09: 0000000000000000 > [ 107.872541] R10: 0000000000000022 R11: 0000000000000246 R12: 00007ffc3160aa24 > [ 107.872542] R13: 000000000041f380 R14: 0000000000000200 R15: 00007f7381200000 > [ 107.872544] > > > Thanks, > Balbir > Thanks, I could reproduce. Had lockdep dropped off so went unnoticed. It is nesting mmap_read_lock in the test suite, I will change that in next version. --Mika