From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AB9EC761A6 for ; Tue, 4 Apr 2023 19:33:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236104AbjDDTdR (ORCPT ); Tue, 4 Apr 2023 15:33:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236105AbjDDTdO (ORCPT ); Tue, 4 Apr 2023 15:33:14 -0400 Received: from mail-ed1-x532.google.com (mail-ed1-x532.google.com [IPv6:2a00:1450:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70A8849D1; Tue, 4 Apr 2023 12:33:12 -0700 (PDT) Received: by mail-ed1-x532.google.com with SMTP id b20so135039639edd.1; Tue, 04 Apr 2023 12:33:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680636791; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=ADWid2t9D+VuAIQH5kZ1bkuTOmJiZU2kCRqFxPkj/Bc=; b=UuWncv9syyeGG4Y//No6XkfwM4SYS2xpKQTWO8haw/hD/bETCY1QrLY5X1zwHCGGuw lKG5uT4mvuUCX93CkdFxTJnRVwq2/Y6C5mXtiau+/1eYq09NBDrzNQKnB2sd8+jO/o72 YjWKtDo7efBcKszqDbOSRWyUdXZzhAb4rir6tiaUGtIWdU+PddqtE2ItrIS0HXuhhHlV wbGpAWoxhucRXESX0S+vRE8jhUk93E4+hF/nNzctyuzuJ+dVxz7U7O+VEqE0MDJWio+U LTNaK32km6Bf9SJrF7c7gvwXu5WiVZ4TN1WgqQPdme5QZtYAuyQo75wcV5BEI7usuftD blWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680636791; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=ADWid2t9D+VuAIQH5kZ1bkuTOmJiZU2kCRqFxPkj/Bc=; b=dEWbivapCmvd0gHU5zAtaz9C00gfNR5FWzzrRchobTk53vKAaWt/WqWRNY/4CdRrcs Uu220yyyJqUvNWIF0Vi17ez4NRWHhAQtjG45lRBOaRAMDU4cm2Gi9nHbULhdjWvYE2GP 4+A8KFiKXa43szZZu+Wo49KfJSw3RPR8UZS9kAWfLffskJs9n9q5geO0RU8kBYRHlNBw c1SvYZYnIYDRbiD21cU/1AQSyIIAzH7AiwFFCj2STQ42oHQl1GiiJPhncGfSOkevIZft PJf39gGLuR+/pu+Msyx4xxuLG+m3WU0mA9hyo5lE5PWcKBjY/HHb3/a8u5p7XZ2n0KMZ Sb2Q== X-Gm-Message-State: AAQBX9d5KigNTovKlF2eLf6fjbCZa/LSN9pYy+3vaojD6jVQYtAqjnnz U/AfboB/BI1QnfNRKgmQwJ0= X-Google-Smtp-Source: AKy350YcpT8yBBP1GJBzn1D6kk6cS4shrfAbfILfucso2ifapdcwIrAgq/cDTNIpC1bXkc7kWCaG1A== X-Received: by 2002:a50:ef18:0:b0:4fa:d83b:f5da with SMTP id m24-20020a50ef18000000b004fad83bf5damr432482eds.30.1680636790457; Tue, 04 Apr 2023 12:33:10 -0700 (PDT) Received: from pc636 ([155.137.26.201]) by smtp.gmail.com with ESMTPSA id r19-20020a50c013000000b004fd29e87535sm6267504edb.14.2023.04.04.12.33.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Apr 2023 12:33:09 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 4 Apr 2023 21:33:07 +0200 To: "Paul E. McKenney" Cc: =?utf-8?B?5Luj5a2Q5Li6IChaaXdlaSBEYWkp?= , "urezki@gmail.com" , "frederic@kernel.org" , "quic_neeraju@quicinc.com" , "josh@joshtriplett.org" , "rostedt@goodmis.org" , "mathieu.desnoyers@efficios.com" , "jiangshanlai@gmail.com" , "joel@joelfernandes.org" , "rcu@vger.kernel.org" , "linux-kernel@vger.kernel.org" , =?utf-8?B?546L5Y+MIChTaHVhbmcgV2FuZyk=?= , =?utf-8?B?6L6b5L6d5YehIChZaWZhbiBYaW4p?= , =?utf-8?B?546L56eRIChLZSBXYW5nKQ==?= , =?utf-8?B?6Zer5a2m5paHIChYdWV3ZW4gWWFuKQ==?= , =?utf-8?B?54mb5b+X5Zu9IChaaGlndW8gTml1KQ==?= , =?utf-8?B?6buE5pyd6ZizIChaaGFveWFuZyBIdWFuZyk=?= Subject: Re: Re: [PATCH V2] rcu: Make sure new krcp free business is handled after the wanted rcu grace period. Message-ID: References: <10f5eb13d7c741c2a0e83ff1d788f398@BJMBX01.spreadtrum.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org > > > My concern is that running the channels separately might mean more grace > > > periods (and thus more energy draw) on nearly idle devices, such devices > > > usually being the ones for which energy efficiency matters most. > > > > > > But perhaps Vlad, Neeraj, or Joel has some insight on this, given > > > that they are the ones working on battery-powered devices. > > > > > > > > Either way, this fixes only one bug of two. The second bug is in the > > > > > kfree_rcu() tests, which should have caught this bug. Thoughts on a good fix > > > > > for those tests? > > > > > > > > I inserted a msleep() between "rcu_read_lock(), get pointer via rcu_dereference()" > > > > and "reference pointer, using the member", at the rcu scenario, then we can > > > > reproduce this issue very soon in stress test. Can kfree_rcu() tests insert msleep()? > > > > > > Another approach is to separate concerns, so that readers interact with > > > grace periods in the rcutorture.c tests, and to add the interaction > > > of to-be-freed memory with grace periods in the rcuscale kvfree tests. > > > I took a step in this direction with this commit on the -rcu tree's > > > "dev" branch: > > > > > > efbe7927f479 ("rcu/kvfree: Add debug to check grace periods") > > > > > > Given this, might it be possible to make rcuscale.c's kfree_rcu() > > > testing create patterns of usage of the three channels so as to > > > catch this bug that way? > > > > > > > I can try it on my k5.15 device, and need some time. > > I have a question. Do you mean add code in tree.c to create pattern > > while channel data is being freed? > > If so, both rcuscales.c and tree.c need to be modified for the test case. > > My thought is to run the test on a system where very little else is > happening, and then creating the temporal pattern only in rcuscale.c. > One way would be to modify kfree_scale_thread(), perhaps using an > additional module parameter using torture_param(). > > But just out of curiosity, what changes were you thinking of making > in tree.c? > OK. I can reproduce it on latest rcu-dev: [ 75.302795] ------------[ cut here ]------------ [ 75.302801] WARNING: CPU: 50 PID: 721 at kernel/rcu/tree.c:3043 kfree_rcu_work+0x157/0x1a0 [ 75.302808] Modules linked in: test_vmalloc(E+) bochs(E) drm_vram_helper(E) snd_pcm(E) drm_ttm_helper(E) ppdev(E) snd_timer(E) joydev(E) ttm(E) drm_kms_helper(E) snd(E) parport_pc(E) soundcore(E) evdev(E) pcspkr(E) sg(E) serio_raw(E) parport(E) drm(E) qemu_fw_cfg(E) button(E) ip_tables(E) x_tables(E) autofs4(E) ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) sd_mod(E) t10_pi(E) crc64_rocksoft(E) crc64(E) crc_t10dif(E) crct10dif_generic(E) sr_mod(E) cdrom(E) crct10dif_common(E) ata_generic(E) ata_piix(E) libata(E) scsi_mod(E) psmouse(E) e1000(E) scsi_common(E) i2c_piix4(E) floppy(E) [ 75.302865] CPU: 50 PID: 721 Comm: kworker/50:1 Kdump: loaded Tainted: G E 6.3.0-rc1+ #58 [ 75.302868] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 75.302870] Workqueue: events kfree_rcu_work [ 75.302905] RIP: 0010:kfree_rcu_work+0x157/0x1a0 [ 75.302907] Code: 8b 05 75 f9 37 01 4c 29 e8 48 83 f8 f8 76 40 48 8b 4c 24 08 48 83 f9 01 74 35 48 8b 05 ca b4 44 01 48 29 c8 48 83 f8 f8 76 25 <0f> 0b 48 8b 44 24 38 65 48 2b 04 25 28 00 00 00 75 23 48 83 c4 40 [ 75.302910] RSP: 0018:ffffbd4642d8bde8 EFLAGS: 00010202 [ 75.302913] RAX: fffffffffffffffc RBX: ffff9f693d5dd140 RCX: 000000000000003c [ 75.302914] RDX: 0000000000000002 RSI: ffffbd4642d8be08 RDI: ffff9f5a4d608000 [ 75.302916] RBP: ffffbd4642d8be08 R08: 0000001188654ff5 R09: 0000000000000000 [ 75.302918] R10: 0000000000000001 R11: 0000000000000001 R12: ffffbd46812d7000 [ 75.302919] R13: 0000000000000260 R14: ffffbd4642d8bdf8 R15: ffff9f5a47637000 [ 75.302922] FS: 0000000000000000(0000) GS:ffff9f693e200000(0000) knlGS:0000000000000000 [ 75.302924] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 75.302926] CR2: 0000562dfe4307d0 CR3: 000000054ba26000 CR4: 00000000000006e0 [ 75.302930] Call Trace: [ 75.302937] [ 75.302942] ? lock_acquire+0xc8/0x1a0 [ 75.302949] process_one_work+0x29d/0x560 [ 75.302957] ? __pfx_worker_thread+0x10/0x10 [ 75.302960] worker_thread+0x52/0x3a0 [ 75.302964] ? __pfx_worker_thread+0x10/0x10 [ 75.302967] kthread+0xe7/0x110 [ 75.302970] ? __pfx_kthread+0x10/0x10 [ 75.302973] ret_from_fork+0x2c/0x50 [ 75.302984] [ 75.302986] ---[ end trace 0000000000000000 ]--- This is with: commit 8f6414680a0d539ca0e7fde80556c71b7b3da88a (HEAD -> dev) Author: Uladzislau Rezki (Sony) Date: Tue Apr 4 15:51:56 2023 +0200 rcu/kvfree: Add debug check of GP ready for ptrs in a list commit efbe7927f47958a6805da5560d9a5f469ba51e73 (origin/dev) Author: Paul E. McKenney Date: Mon Apr 3 16:49:14 2023 -0700 rcu/kvfree: Add debug to check grace periods + below revert commit 6b4fef6ec689b1dda9c63be77e9a81a52cc39dc1 Author: Ziwei Dai Date: Fri Mar 31 20:42:09 2023 +0800 rcu/kvfree: Avoid freeing new kfree_rcu() memory after old grace period The test is "sudo ./test_vmalloc.sh run_test_mask=768 nr_threads=64&" it runs single argument and double argument to free vmalloc ptrs., number of threads are 64: without revert(with a patch that is in question), i am not able to reproduce it anymore. -- Uladzislau Rezki