From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0DC7A2D3204 for ; Wed, 13 Aug 2025 07:42:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755070952; cv=none; b=rsSfxyGr2YTkldhfXSxnK+ewfhLJ9cq68oScgkdVd1rPekd+U0n/K+qmZO0oJ1uxxn0QWXK35sCxCpf+AUPxUdOIWSmC57WgSg51OP2v3QcumpVAh8WK+ZGT4lUHqKV3ke3BipTH3Isy/w5HwGWi6poWt4BYIhY2vePUzbZ0OpM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755070952; c=relaxed/simple; bh=HdN0XMRFktS6aaDUEEo85Pl2LmbyxkiHp3apivFUIDk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uhWxvz4LezqAWIR0hIzfJUDDm9r9YYkCDPV+/QbJoMdPC6tbzusm2YGGVtlROfoPC2LQ0ZhqW2PqlZN0jJxULft5x6UVJ9naGrRshUcoWFe8iMFEvAmmeku7GOJUaLBUxWvBsqrVPpRP0zfVPus6bK26PKNpG4kJj/IgnswaLlc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kzalloc.com; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.210.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kzalloc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-73de140046eso463884b3a.1 for ; Wed, 13 Aug 2025 00:42:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1755070950; x=1755675750; h=content-transfer-encoding:in-reply-to:organization:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=SpiYdySHhrFSLFvt+ZXWlE3IvVelgPZB7slyigr8p3I=; b=Omazhgc8XZ/huK65PO/VrhAaar4XvBxKwyV2gbrwJ/Yo8AxBr8nC6+l2Eda5NkbmMR Juis8A3lzOTQMFXcFkt0wBIns6oWnjaswZI1BPwIW9JiJmLF50VTmevNCR3jLD91905m XLjxxhqxuo84I4JiqsUPxk9KOQCPbnfQLI85qsMJsgj3fDQ2JW4DvLD7Gv2QetnVwg+n HsOnsbYQ9XOreGI5UBcxkCulaX3l5dq33Y2dxPA2aXx2XI99L9srQkFT2izq7UTk0GSX dczgKB1TSMzwd2VrP81dP81YZbcOz5eKwUxp1vLT0syBgdUpedTO8KTDmTOeSX2VvstD zkoA== X-Forwarded-Encrypted: i=1; AJvYcCWpV213TfLSb9WLQsNaxsQSc2dPda6xEK4Ye829ZayUo9geyY958JDhWc7kKvA+HJvyetjSqug=@vger.kernel.org X-Gm-Message-State: AOJu0YxpArcIJ1kOEpbvaTKCn4UCExbt31i2+EOu6vhiUg91diyV/Udz 2HW5JDE6Y2weJ2DsHZGuZZAdg7vSIF9qqdT7oVtqOSIafsBZU3wwurdQ X-Gm-Gg: ASbGncv3onfn/xGr5yMi/iccXPHLnGdHRSZibb5Wos3+pIDEyMAm74aSXnDXQtBLrQX 74W6V0VMTDM4QXBLu5FuoB7ANzxnXo+7/M7NHlH7k9wG1qNM+2eByFtHvAxSzMGjqgz8GOlONeq MLvhA3+WrUIf2w8Nz9RF8GDPonFTx6i6UNjkwAvTilDxU7iVMB9kS1JnrrMDXTltvF/wms5OsrZ UddpwCDETN+HwXu2CkyTlpNevNQPgi0eLjxcWBGZEo0OuxMAj4jR3Q/Qg74+JYTpzahI9WIJ50I iOKqh801ZJ3tcv107OjJDJHYd5cBZdNxlJNR3b9+eRx/p8C2/gwapU8VqDaAjngRAeJsWrkByc6 uQ+JCH4fGKSVPskHE3b7cnCjtphsb/CLT X-Google-Smtp-Source: AGHT+IFyRulOk2yEiytouE8c1ifGVIrW23F74ZO8AVJB/Bv0ruH/ZKMqF0l+0q/T60XygCbCXcCjWw== X-Received: by 2002:a17:90b:224f:b0:31f:23f0:2df8 with SMTP id 98e67ed59e1d1-321d0ecb6aamr1294794a91.6.1755070950304; Wed, 13 Aug 2025 00:42:30 -0700 (PDT) Received: from [192.168.50.136] ([118.32.98.101]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b429920ab6dsm11951099a12.58.2025.08.13.00.42.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Aug 2025 00:42:29 -0700 (PDT) Message-ID: <17f91b9a-0a3a-47e1-bdfb-06237ae5da55@kzalloc.com> Date: Wed, 13 Aug 2025 16:42:24 +0900 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [BUG] arm64: Sleeping function called from invalid context in do_debug_exception on PREEMPT_RT To: Yeoreum Yun Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Mark Rutland , Naresh Kamboju , "Paul E. McKenney" , Masami Hiramatsu , Austin Kim , linux-rt-devel@lists.linux.dev, syzkaller@googlegroups.com, stable@vger.kernel.org References: Content-Language: en-US From: Yunseong Kim Organization: kzalloc In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Yeoreum, Thank you for pointing it! On 8/13/25 3:56 PM, Yeoreum Yun wrote: > Hi Yunseong, > >> >> | BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 >> | in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20466, name: syz.0.1689 >> | preempt_count: 1, expected: 0 >> | RCU nest depth: 0, expected: 0 >> | Preemption disabled at: >> | [] debug_exception_enter arch/arm64/mm/fault.c:978 [inline] >> | [] do_debug_exception+0x68/0x2fc arch/arm64/mm/fault.c:997 >> | CPU: 0 UID: 0 PID: 20466 Comm: syz.0.1689 Not tainted 6.16.0-rc1-rt1-dirty #12 PREEMPT_RT >> | Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8 05/13/2025 >> | Call trace: >> | show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C) >> | __dump_stack+0x30/0x40 lib/dump_stack.c:94 >> | dump_stack_lvl+0x148/0x1d8 lib/dump_stack.c:120 >> | dump_stack+0x1c/0x3c lib/dump_stack.c:129 >> | __might_resched+0x2e4/0x52c kernel/sched/core.c:8800 >> | __rt_spin_lock kernel/locking/spinlock_rt.c:48 [inline] >> | rt_spin_lock+0xa8/0x1bc kernel/locking/spinlock_rt.c:57 >> | spin_lock include/linux/spinlock_rt.h:44 [inline] >> | force_sig_info_to_task+0x6c/0x4a8 kernel/signal.c:1302 >> | force_sig_fault_to_task kernel/signal.c:1699 [inline] >> | force_sig_fault+0xc4/0x110 kernel/signal.c:1704 >> | arm64_force_sig_fault+0x6c/0x80 arch/arm64/kernel/traps.c:265 >> | send_user_sigtrap arch/arm64/kernel/debug-monitors.c:237 [inline] >> | single_step_handler+0x1f4/0x36c arch/arm64/kernel/debug-monitors.c:257 >> | do_debug_exception+0x154/0x2fc arch/arm64/mm/fault.c:1002 >> | el0_dbg+0x44/0x120 arch/arm64/kernel/entry-common.c:756 >> | el0t_64_sync_handler+0x3c/0x108 arch/arm64/kernel/entry-common.c:832 >> | el0t_64_sync+0x1ac/0x1b0 arch/arm64/kernel/entry.S:600 >> >> >> It seems that commit eaff68b32861 ("arm64: entry: Add entry and exit functions >> for debug exception") in 6.17-rc1, also present as 6fb44438a5e1 in mainline, >> removed code that previously avoided sleeping context issues when handling >> debug exceptions: >> Link: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/arch/arm64/mm/fault.c?id=eaff68b3286116d499a3d4e513a36d772faba587 > > No. Her patch commit 31575e11ecf7 (arm64: debug: split brk64 exception entry) > solves your splat since el0_brk64() doesn't call debug_exception_enter() > by spliting el0/el1 brk64 entry exception entry. > > Formerly, el(0/1)_dbg() are handled in do_debug_exception() together > and it calls debug_exception_enter() disabling preemption and this makes > your splat while handling brk excepttion from el0. > Do you think a fix is necessary if this issue also affects the LTS kernel before 6.17-rc1? As far as I know, most production RT kernels are still based on the existing LTS versions. > > -- > Sincerely, > Yeoreum Yun Thank you, Yunseong