From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f169.google.com (mail-yb1-f169.google.com [209.85.219.169]) (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 AE0B98528E for ; Tue, 19 Nov 2024 19:02:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732042961; cv=none; b=rWtsWxFf5tY6YFDTOPP+hpJgNeXoRfMWedXD39+FffuG7KyIxDIV1r1Y3i8/n970isTci2ljA6RRJEAhGrD6lI+lEgeyrSKGh8lCt2MJ+u0zaEaKCclHIfhvupPEgMAYuqWllcGmcswmY1tjzESCbOgipnB03ztGLP9ZODoNAvo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732042961; c=relaxed/simple; bh=y+UxJkEPesqMLF84U+t/E/lqQVamvm5QAcaft0yOS8Q=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=cRjMFH/lIdn0d1b/nKHMiAoWYsOvFNe3H2XXe/VaoG7x/Mtx6O5qezQwj2u0HHZW5Vpei8RETWapqWLet81wdzMCOYb16eYvNGwHcpUcfVwlttnXXcHVdeYOzLTNO4B347rSC51UBFW2r52dM0lTBU5YGGwAHeerTGJYHX533E4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.219.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-yb1-f169.google.com with SMTP id 3f1490d57ef6-e383bbcef9dso1266556276.3 for ; Tue, 19 Nov 2024 11:02:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732042958; x=1732647758; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=m0fp0XnUxNxL7PZB7gv+woUGcpwTbov1O1u2skS2Vxo=; b=Z3OWF5hTmrGbILSv/tfXIuJEF4FQ5xW0D6YWptyohADIMEi8TCYPw1/CuPHqDqB7Rp hCl6q8stx2OF1jKxlsnILeGFx7Cc6CEO+qiOJ9o64aEP0ZfshdBW/lvC4WIfWCLFh4XO IEkHUT4K8LqzSFv6DX10hRkgUVFW+RspuqTXNsnTqhdKZqkrtwCCHzGjHParlnmt1qde cAjdMFFUV+WsyyC+iF6z9G5Cti2UyjfnK5YJ/M3UKaTMgxV3t+IHP20py4clPLdCTLga HzKlm7cvrRNZLrPNoVfMapBhr7osAvxV8F9mWNtUO0Mzdhnv7xu93B7hjt/vVMbYendT QDlw== X-Forwarded-Encrypted: i=1; AJvYcCU1FyDoMLrSLcOtngJoy9vilkgENkeNxsG3WyhA9SxI0VNXebyfJZc4I6DCh6WcLGlvlPgFvqg2hw==@vger.kernel.org X-Gm-Message-State: AOJu0YxwArJUttS1kv0eMU5wiccAEbprNs6jhbzvQruJkyhji7HfRGSm AmCC4cv2YhVOPWOvpaxcw/o6Ozu10ZisGxg+aLjW+dRrno5XzUWq0WaU7AD0 X-Google-Smtp-Source: AGHT+IGQTzkgysPiL7jyP9/KCzjorSDHup0yEUdZcd/EdZtIgoBxXqb5Ago1OrPS2zMf8mQNszYKBw== X-Received: by 2002:a05:6902:b20:b0:e30:d4a2:222a with SMTP id 3f1490d57ef6-e382637937amr9714371276.31.1732042958200; Tue, 19 Nov 2024 11:02:38 -0800 (PST) Received: from mail-yb1-f181.google.com (mail-yb1-f181.google.com. [209.85.219.181]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e387e7419ffsm2632575276.22.2024.11.19.11.02.37 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Nov 2024 11:02:37 -0800 (PST) Received: by mail-yb1-f181.google.com with SMTP id 3f1490d57ef6-e383bbcef9dso1266521276.3 for ; Tue, 19 Nov 2024 11:02:37 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCXQFyfHdPDwO1AzvQZoIJnloq5b8mcf27YcfnogWBH5J4vRdF4U44hNI5DjyLotrlRee4eYiS54qg==@vger.kernel.org X-Received: by 2002:a05:690c:6404:b0:6ee:6e8e:6f84 with SMTP id 00721157ae682-6ee6e8e71ddmr133325447b3.12.1732042957570; Tue, 19 Nov 2024 11:02:37 -0800 (PST) Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20241029152249.667290-1-axboe@kernel.dk> <20241029152249.667290-4-axboe@kernel.dk> <37c588d4-2c32-4aad-a19e-642961f200d7@roeck-us.net> <5a7528c4-4391-4bd9-bbdb-a0247f3c76a9@kernel.dk> In-Reply-To: <5a7528c4-4391-4bd9-bbdb-a0247f3c76a9@kernel.dk> From: Geert Uytterhoeven Date: Tue, 19 Nov 2024 20:02:25 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 03/14] io_uring: specify freeptr usage for SLAB_TYPESAFE_BY_RCU io_kiocb cache To: Jens Axboe Cc: Guenter Roeck , io-uring@vger.kernel.org, linux-m68k Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Jens. On Tue, Nov 19, 2024 at 8:00=E2=80=AFPM Jens Axboe wrote: > On 11/19/24 10:49 AM, Geert Uytterhoeven wrote: > > On Tue, Nov 19, 2024 at 5:21?PM Guenter Roeck wrot= e: > >> On 11/19/24 08:02, Jens Axboe wrote: > >>> On 11/19/24 8:36 AM, Guenter Roeck wrote: > >>>> On Tue, Oct 29, 2024 at 09:16:32AM -0600, Jens Axboe wrote: > >>>>> Doesn't matter right now as there's still some bytes left for it, b= ut > >>>>> let's prepare for the io_kiocb potentially growing and add a specif= ic > >>>>> freeptr offset for it. > >>>>> > >>>>> Signed-off-by: Jens Axboe > >>>> > >>>> This patch triggers: > >>>> > >>>> Kernel panic - not syncing: __kmem_cache_create_args: Failed to crea= te slab 'io_kiocb'. Error -22 > >>>> CPU: 0 UID: 0 PID: 1 Comm: swapper Not tainted 6.12.0-mac-00971-g158= f238aa69d #1 > >>>> Stack from 00c63e5c: > >>>> 00c63e5c 00612c1c 00612c1c 00000300 00000001 005f3ce6 004b9= 044 00612c1c > >>>> 004ae21e 00000310 000000b6 005f3ce6 005f3ce6 ffffffea fffff= fea 00797244 > >>>> 00c63f20 000c6974 005ee588 004c9051 005f3ce6 ffffffea 00000= 0a5 00c614a0 > >>>> 004a72c2 0002cb62 000c675e 004adb58 0076f28a 005f3ce6 00000= 0b6 00c63ef4 > >>>> 00000310 00c63ef4 00000000 00000016 0076f23e 00c63f4c 00000= 010 00000004 > >>>> 00000038 0000009a 01000000 00000000 00000000 00000000 00002= 0e0 0076f23e > >>>> Call Trace: [<004b9044>] dump_stack+0xc/0x10 > >>>> [<004ae21e>] panic+0xc4/0x252 > >>>> [<000c6974>] __kmem_cache_create_args+0x216/0x26c > >>>> [<004a72c2>] strcpy+0x0/0x1c > >>>> [<0002cb62>] parse_args+0x0/0x1f2 > >>>> [<000c675e>] __kmem_cache_create_args+0x0/0x26c > >>>> [<004adb58>] memset+0x0/0x8c > >>>> [<0076f28a>] io_uring_init+0x4c/0xca > >>>> [<0076f23e>] io_uring_init+0x0/0xca > >>>> [<000020e0>] do_one_initcall+0x32/0x192 > >>>> [<0076f23e>] io_uring_init+0x0/0xca > >>>> [<0000211c>] do_one_initcall+0x6e/0x192 > >>>> [<004a72c2>] strcpy+0x0/0x1c > >>>> [<0002cb62>] parse_args+0x0/0x1f2 > >>>> [<000020ae>] do_one_initcall+0x0/0x192 > >>>> [<0075c4e2>] kernel_init_freeable+0x1a0/0x1a4 > >>>> [<0076f23e>] io_uring_init+0x0/0xca > >>>> [<004b911a>] kernel_init+0x0/0xec > >>>> [<004b912e>] kernel_init+0x14/0xec > >>>> [<004b911a>] kernel_init+0x0/0xec > >>>> [<0000252c>] ret_from_kernel_thread+0xc/0x14 > >>>> > >>>> when trying to boot the m68k:q800 machine in qemu. > >>>> > >>>> An added debug message in create_cache() shows the reason: > >>>> > >>>> #### freeptr_offset=3D154 object_size=3D182 flags=3D0x310 aligned=3D= 0 sizeof(freeptr_t)=3D4 > >>>> > >>>> freeptr_offset would need to be 4-byte aligned but that is not the > >>>> case on m68k. > >>> > >>> Why is ->work 2-byte aligned to begin with on m68k?! > >> > >> My understanding is that m68k does not align pointers. > > > > The minimum alignment for multi-byte integral values on m68k is > > 2 bytes. > > > > See also the comment at > > https://elixir.bootlin.com/linux/v6.12/source/include/linux/maple_tree.= h#L46 > > Maybe it's time we put m68k to bed? :-) > > We can add a forced alignment ->work to be 4 bytes, won't change > anything on anything remotely current. But does feel pretty hacky to > need to align based on some ancient thing. Why does freeptr_offset need to be 4-byte aligned? Gr{oetje,eeting}s, Geert --=20 Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k= .org In personal conversations with technical people, I call myself a hacker. Bu= t when I'm talking to journalists I just say "programmer" or something like t= hat. -- Linus Torvalds