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Biederman" References: <00000000000063692b05cb493f6d@google.com> <20210906103309.f4152941a9a00a27f62dbc2b@linux-foundation.org> <59af1f1c-ae77-cfec-8d8c-32368f8ffdb6@redhat.com> From: Guenter Roeck Subject: Re: [syzbot] BUG: soft lockup in handle_mm_fault (2) Message-ID: Date: Mon, 6 Sep 2021 11:53:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <59af1f1c-ae77-cfec-8d8c-32368f8ffdb6@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="K1/glI5P"; spf=pass (imf22.hostedemail.com: domain of groeck7@gmail.com designates 209.85.167.180 as permitted sender) smtp.mailfrom=groeck7@gmail.com; dmarc=none X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 51DE11901 X-Stat-Signature: ksouxudmjin59meh8s6b8a64jcbg3pwa X-HE-Tag: 1630954410-875537 Content-Transfer-Encoding: quoted-printable 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 9/6/21 10:46 AM, David Hildenbrand wrote: > On 06.09.21 19:33, Andrew Morton wrote: >> (cc's added) >> >> On Sun, 05 Sep 2021 18:05:40 -0700 syzbot wrote: >> >>> Hello, >>> >>> syzbot found the following issue on: >>> >>> HEAD commit:=C2=A0=C2=A0=C2=A0 49624efa65ac Merge tag 'denywrite-for-= 5.15' of git://githu.. >>> git tree:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 upstream >>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D12eff4b33= 00000 >>> kernel config:=C2=A0 https://syzkaller.appspot.com/x/.config?x=3Dc598= 149362d97396 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=3Daa7a876b810= 8f1622bc3 >>> compiler:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 aarch64-linux-gnu-gcc (= Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1 >>> userspace arch: arm64 >>> >>> Unfortunately, I don't have any reproducer for this issue yet. >>> >>> IMPORTANT: if you fix the issue, please add the following tag to the = commit: >>> Reported-by: syzbot+aa7a876b8108f1622bc3@syzkaller.appspotmail.com >>> >>> watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:264= 49] >>> Modules linked in: >>> irq event stamp: 248 >>> hardirqs last=C2=A0 enabled at (247): [] __exit_to_= kernel_mode arch/arm64/kernel/entry-common.c:81 [inline] >>> hardirqs last=C2=A0 enabled at (247): [] exit_to_ke= rnel_mode+0x38/0x230 arch/arm64/kernel/entry-common.c:91 >>> hardirqs last disabled at (248): [] enter_el1_irq_o= r_nmi+0x10/0x20 arch/arm64/kernel/entry-common.c:227 >>> softirqs last=C2=A0 enabled at (182): [] _stext+0x9= 64/0xff8 >>> softirqs last disabled at (41): [] do_softirq_own_s= tack include/asm-generic/softirq_stack.h:10 [inline] >>> softirqs last disabled at (41): [] invoke_softirq k= ernel/softirq.c:439 [inline] >>> softirqs last disabled at (41): [] __irq_exit_rcu+0= x208/0x4f0 kernel/softirq.c:636 >>> CPU: 0 PID: 26449 Comm: syz-executor.1 Not tainted 5.14.0-syzkaller-0= 9416-g49624efa65ac #0 >>> Hardware name: linux,dummy-virt (DT) >>> pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=3D--) >>> pc : clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:23 >>> lr : clear_highpage include/linux/highmem.h:181 [inline] >>> lr : kernel_init_free_pages.part.0+0x6c/0x17c mm/page_alloc.c:1286 >>> sp : ffff800019be75e0 >>> x29: ffff800019be75e0 x28: 0000000000000000 x27: 0000000000000000 >>> x26: ffff000009d64940 x25: ffff6000013ac928 x24: 00000000000014c0 >>> x23: ffff000009d63480 x22: fffffc0000173340 x21: ffff800015794a78 >>> x20: dfff800000000000 x19: fffffc0000173300 x18: 0000000000000000 >>> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 >>> x14: 1ffff0000337ce86 x13: 0000000000000013 x12: ffff7f800002e667 >>> x11: 1fffff800002e666 x10: ffff7f800002e666 x9 : 0000000000000000 >>> x8 : ffff600000b99a00 x7 : 0000000000000000 x6 : 000000000000003f >>> x5 : 0000000000000040 x4 : 1ffff00003060d98 x3 : 1fffe000013ac691 >>> x2 : 0000000000000004 x1 : 0000000000000040 x0 : ffff000005ccc880 >>> Call trace: >>> =C2=A0 clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:21 >>> =C2=A0 kernel_init_free_pages mm/page_alloc.c:1283 [inline] >>> =C2=A0 post_alloc_hook+0x1ac/0x25c mm/page_alloc.c:2426 >>> =C2=A0 prep_new_page mm/page_alloc.c:2436 [inline] >>> =C2=A0 get_page_from_freelist+0x184c/0x2320 mm/page_alloc.c:4168 >>> =C2=A0 __alloc_pages+0x1a8/0x21d0 mm/page_alloc.c:5390 >>> =C2=A0 alloc_pages_vma+0xbc/0x530 mm/mempolicy.c:2252 >>> =C2=A0 alloc_zeroed_user_highpage_movable+0x9c/0xd0 arch/arm64/mm/fau= lt.c:926 >>> =C2=A0 do_anonymous_page mm/memory.c:3767 [inline] >>> =C2=A0 handle_pte_fault mm/memory.c:4556 [inline] >>> =C2=A0 __handle_mm_fault+0xbc4/0x2210 mm/memory.c:4693 >>> =C2=A0 handle_mm_fault+0x1dc/0x4f0 mm/memory.c:4791 >>> =C2=A0 __do_page_fault arch/arm64/mm/fault.c:499 [inline] >>> =C2=A0 do_page_fault+0x230/0x8c0 arch/arm64/mm/fault.c:599 >>> =C2=A0 do_translation_fault+0x1a4/0x210 arch/arm64/mm/fault.c:680 >>> =C2=A0 do_mem_abort+0x64/0x1c0 arch/arm64/mm/fault.c:813 >>> =C2=A0 el0_da+0x7c/0x2b0 arch/arm64/kernel/entry-common.c:481 >>> =C2=A0 el0t_64_sync_handler+0x168/0x1b0 arch/arm64/kernel/entry-commo= n.c:616 >>> =C2=A0 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:572 >=20 > At first sight, looks unrelated. Being stuck in clear_page() is weird; = we're running inside a VM ("dummy-virt"), whereby such stuck tasks in the= guests are sometimes the result of the hypervisor being stuck (e.g., hea= vily overcommitted). >=20 Unrelated to your series, yes, because it was first reported after commit= ebf435d3b51b ("Merge tag 'staging-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kern= el/git/gregkh/staging") which predates your series. > If we don't get a reproducer, that's most probably the root cause. Let'= s see. >=20 That seems unlikely. The problem was seen 8 times by now, starting Septem= ber 2. Guenter