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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q46vtueO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q46vtueO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B27E4C4CEC5; Sun, 13 Oct 2024 13:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728826149; bh=vr05ydl+l3Q8vbbJWJVpp5PqMypHjJjrahJHwSqSpyU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Q46vtueOfgWVmOtY2fTyxsJa+4ceOftJTy1keVb9sfDj+c6o3QAUPb6PVCPgxQ0np 5buN0XQJsfr+wEY8hFaUG6oMRB/JON3oYt/A0RIBobeyuxIyxuletHrTu3Bf6iO9HO KPYAPTAImJPV8JaTkwnm4BFdXHy39F+uRS9cK7vamLbfJ3qVIBCI6IMN40fTdpiyHa wB1yTUx+PeiU2SaaUQpbk/zztFjMp3d1wo0qjnz0UKm+r/Sr/npiYVlwny4vyIoDOM Rfzt2Ikop8HhE6j7Z6xI142PfgYmBgHTJT9E3K6rPAI/qm1h2KPx6x0SU/aWvXSTvl 1+4TD8/gnP3Cw== Date: Sun, 13 Oct 2024 09:29:08 -0400 From: Sasha Levin To: Lorenzo Stoakes Cc: syzbot , Liam.Howlett@oracle.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, vbabka@suse.cz Subject: Re: [syzbot] [mm?] INFO: task hung in exit_mmap Message-ID: References: <6707f080.050a0220.64b99.001c.GAE@google.com> <72188763-843c-4e83-a25a-90be2d0bf9c0@lucifer.local> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <72188763-843c-4e83-a25a-90be2d0bf9c0@lucifer.local> On Thu, Oct 10, 2024 at 04:28:18PM +0100, Lorenzo Stoakes wrote: >On Thu, Oct 10, 2024 at 08:19:28AM -0700, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: d3d1556696c1 Merge tag 'mm-hotfixes-stable-2024-10-09-15-4.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=10416fd0580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=7a3fccdd0bb995 >> dashboard link: https://syzkaller.appspot.com/bug?extid=39bc767144c55c8db0ea >> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/0600b551e610/disk-d3d15566.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/d59d43ed3976/vmlinux-d3d15566.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/e686a3e7e0d6/bzImage-d3d15566.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+39bc767144c55c8db0ea@syzkaller.appspotmail.com >> >> INFO: task syz.3.917:7739 blocked for more than 146 seconds. >> Not tainted 6.12.0-rc2-syzkaller-00074-gd3d1556696c1 #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz.3.917 state:D stack:23808 pid:7739 tgid:7739 ppid:5232 flags:0x00004000 >> Call Trace: >> >> context_switch kernel/sched/core.c:5322 [inline] >> __schedule+0x1843/0x4ae0 kernel/sched/core.c:6682 >> __schedule_loop kernel/sched/core.c:6759 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6774 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6831 >> rwsem_down_write_slowpath+0xeee/0x13b0 kernel/locking/rwsem.c:1176 >> __down_write_common kernel/locking/rwsem.c:1304 [inline] >> __down_write kernel/locking/rwsem.c:1313 [inline] >> down_write+0x1d7/0x220 kernel/locking/rwsem.c:1578 >> mmap_write_lock include/linux/mmap_lock.h:106 [inline] >> exit_mmap+0x2bd/0xc40 mm/mmap.c:1872 > >Hmm, task freezing up or system becoming unstable/locked up is reminsecent >of the maple tree bug I fixed in [0], which is still in the unstable hotfix >branch. > >This is likely not going to repro as it's quite heisenbug-ish to trigger >and the failures are like this - somewhat disconnected from the cause, so >not sure if there is any case to speed this to Linus's tree. > >On the other hand it's a pretty serious problem for stability and likely to >continue to manifest in nasty ways like this. > >Can't be 100% sure this is the cause, but seems likely. > >[0]:https://lore.kernel.org/linux-mm/48b349a2a0f7c76e18772712d0997a5e12ab0a3b.1728314403.git.lorenzo.stoakes@oracle.com/ On my Debian build box, running a 6.1 kernel, I've started hitting a similar issue: Oct 12 17:24:01 debian kernel: INFO: task sed:3557356 blocked for more than 1208 seconds. Oct 12 17:24:01 debian kernel: Not tainted 6.1.0-26-amd64 #1 Debian 6.1.112-1 Oct 12 17:24:01 debian kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct 12 17:24:01 debian kernel: task:sed state:D stack:0 pid:3557356 ppid:1 flags:0x00000002 Oct 12 17:24:01 debian kernel: Call Trace: Oct 12 17:24:01 debian kernel: Oct 12 17:24:01 debian kernel: __schedule+0x34d/0x9e0 Oct 12 17:24:01 debian kernel: schedule+0x5a/0xd0 Oct 12 17:24:01 debian kernel: rwsem_down_write_slowpath+0x311/0x6d0 Oct 12 17:24:01 debian kernel: exit_mmap+0xf6/0x2f0 Oct 12 17:24:01 debian kernel: __mmput+0x3e/0x130 Oct 12 17:24:01 debian kernel: do_exit+0x2fc/0xaf0 Oct 12 17:24:01 debian kernel: do_group_exit+0x2d/0x80 Oct 12 17:24:01 debian kernel: __x64_sys_exit_group+0x14/0x20 Oct 12 17:24:01 debian kernel: do_syscall_64+0x55/0xb0 Oct 12 17:24:01 debian kernel: ? do_fault+0x1a4/0x410 Oct 12 17:24:01 debian kernel: ? __handle_mm_fault+0x660/0xfa0 Oct 12 17:24:01 debian kernel: ? exit_to_user_mode_prepare+0x40/0x1e0 Oct 12 17:24:01 debian kernel: ? handle_mm_fault+0xdb/0x2d0 Oct 12 17:24:01 debian kernel: ? do_user_addr_fault+0x1b0/0x550 Oct 12 17:24:01 debian kernel: ? exit_to_user_mode_prepare+0x40/0x1e0 Oct 12 17:24:01 debian kernel: entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Oct 12 17:24:01 debian kernel: RIP: 0033:0x7f797d75a349 Oct 12 17:24:01 debian kernel: RSP: 002b:00007fff37f0d3c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 Oct 12 17:24:01 debian kernel: RAX: ffffffffffffffda RBX: 00007f797d8549e0 RCX: 00007f797d75a349 Oct 12 17:24:01 debian kernel: RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000 Oct 12 17:24:01 debian kernel: RBP: 0000000000000000 R08: fffffffffffffe98 R09: 00007fff37f0d2df Oct 12 17:24:01 debian kernel: R10: 00007fff37f0d240 R11: 0000000000000246 R12: 00007f797d8549e0 Oct 12 17:24:01 debian kernel: R13: 00007f797d85a2e0 R14: 0000000000000002 R15: 00007f797d85a2c8 Oct 12 17:24:01 debian kernel: It reproduces fairly easily during a kernel build... It doesn't sound like the same issue you're pointing out, right Lorenzo? -- Thanks, Sasha