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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B9F14D262B2 for ; Wed, 21 Jan 2026 07:16:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 24CAC6B0005; Wed, 21 Jan 2026 02:16:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1FAF96B0088; Wed, 21 Jan 2026 02:16:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0DC8C6B0089; Wed, 21 Jan 2026 02:16:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id EEB2A6B0005 for ; Wed, 21 Jan 2026 02:16:27 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id A5ABF160141 for ; Wed, 21 Jan 2026 07:16:27 +0000 (UTC) X-FDA: 84355112814.07.447E65B Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf05.hostedemail.com (Postfix) with ESMTP id 79703100002 for ; Wed, 21 Jan 2026 07:16:25 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="lCh/8K1a"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=R1GCO+UG; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="lCh/8K1a"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=R1GCO+UG; dmarc=none; spf=pass (imf05.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1768979785; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=/usHWUFZWwt24U9Yjv0VfEz0DO1g3eDaD4Ua5kdbMqM=; b=nsyuh92L/guS68ZlQu4MDoCX8owUdFkqE+Kbzaz0xOgNuQ+dT0IR/mTT41ZIsTZ/X0ZMQf pcn3cbds8Teq1Y+3eUZ4zdt+1I9CIoVzTv5GB96jo556BKLqxv9otApq7384eYFjpaHaqX G+LCW5gx1iuxSRzxmhmyczRwyXYH4dg= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768979785; a=rsa-sha256; cv=none; b=mpPeh1wrfnSy4CnDvrl8zUK8F5iqZ5LOGfuitCgPouND4Ov+2tZZWGUnFRG+nxiYVH0Eq7 l/rvsy5583tjvRdFaxZvL2ymjLngswSEw31/HLuV07KBWYCxwOTg+43h3rtgM9p9nklv74 BxUGCfn3I4+BU/+bHZzgUvJY+n5XOKM= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="lCh/8K1a"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=R1GCO+UG; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="lCh/8K1a"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=R1GCO+UG; dmarc=none; spf=pass (imf05.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B2FD333689; Wed, 21 Jan 2026 07:16:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1768979783; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/usHWUFZWwt24U9Yjv0VfEz0DO1g3eDaD4Ua5kdbMqM=; b=lCh/8K1a9jNDAtVaUkabanAAgGWcOuQWUpwWCIrfHiKmOHSzI8xZw/GMmW+aeB34JSl5bt mSph2FeDJyvnWMCXs7ry/soqtlhTArPyt+utoypWQdpM2vDNuzLcEviTkBq9ENXYgHqquV 6ysjPALlK7Tbmgv+p04WmSZ/+9Wa+Lg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1768979783; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/usHWUFZWwt24U9Yjv0VfEz0DO1g3eDaD4Ua5kdbMqM=; b=R1GCO+UGau5+fc8bT/sx9YhTRHRWqVVYBhWyi7sR7aMbT98OGfwPWNnEZcO8wmyNeV7xzz EWhcrn6WsnEnxVDQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1768979783; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/usHWUFZWwt24U9Yjv0VfEz0DO1g3eDaD4Ua5kdbMqM=; b=lCh/8K1a9jNDAtVaUkabanAAgGWcOuQWUpwWCIrfHiKmOHSzI8xZw/GMmW+aeB34JSl5bt mSph2FeDJyvnWMCXs7ry/soqtlhTArPyt+utoypWQdpM2vDNuzLcEviTkBq9ENXYgHqquV 6ysjPALlK7Tbmgv+p04WmSZ/+9Wa+Lg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1768979783; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/usHWUFZWwt24U9Yjv0VfEz0DO1g3eDaD4Ua5kdbMqM=; b=R1GCO+UGau5+fc8bT/sx9YhTRHRWqVVYBhWyi7sR7aMbT98OGfwPWNnEZcO8wmyNeV7xzz EWhcrn6WsnEnxVDQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id A13543EA63; Wed, 21 Jan 2026 07:16:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id YvLaJkd9cGn2OAAAD6G6ig (envelope-from ); Wed, 21 Jan 2026 07:16:23 +0000 Message-ID: Date: Wed, 21 Jan 2026 08:16:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Possible KCSAN/lockdep issue in -next barns Content-Language: en-US To: Harry Yoo , "Paul E. McKenney" Cc: linux-mm@kvack.org References: From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 79703100002 X-Rspamd-Server: rspam12 X-Stat-Signature: yyn1ez6c1ydn7bozhf3tgxi81x5bcawu X-HE-Tag: 1768979785-466568 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On 1/21/26 08:06, Harry Yoo wrote: > On Tue, Jan 20, 2026 at 09:41:14PM -0800, Paul E. McKenney wrote: >> Hello, Vlastimil, >> >> On the off-chance that this is useful new news. This happened in >> rcutorture's TREE04 scenario running with KCSAN and lockdep enabled. >> >> Thoughts? >> >> Thanx, Paul >> >> ------------------------------------------------------------------------ >> >> [ 253.872153] ============================= >> [ 253.872271] [ BUG: Invalid wait context ] >> [ 253.872271] 6.19.0-rc6-next-20260120 #21508 Not tainted >> [ 253.875774] ----------------------------- >> [ 253.877983] migration/1/23 is trying to lock: >> [ 253.877983] ffff8afd01054e98 (&barn->lock){..-.}-{3:3}, at: barn_get_empty_sheaf+0x1d/0xb0 >> [ 253.877983] other info that might help us debug this: >> [ 253.877983] context-{5:5} >> [ 253.877983] 3 locks held by migration/1/23: >> [ 253.877983] #0: ffff8afd01fd89a8 (&p->pi_lock){-.-.}-{2:2}, at: __balance_push_cpu_stop+0x3f/0x200 >> [ 253.877983] #1: ffffffff9f15c5c8 (rcu_read_lock){....}-{1:3}, at: cpuset_cpus_allowed_fallback+0x27/0x250 >> [ 253.877983] #2: ffff8afd1f470be0 ((local_lock_t *)&pcs->lock){+.+.}-{3:3}, at: __kfree_rcu_sheaf+0x52/0x3d0 >> [ 253.877983] stack backtrace: >> [ 253.877983] CPU: 1 UID: 0 PID: 23 Comm: migration/1 Not tainted 6.19.0-rc6-next-20260120 #21508 PREEMPTLAZY >> [ 253.877983] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 >> [ 253.877983] Stopper: __balance_push_cpu_stop+0x0/0x200 <- balance_push+0x118/0x170 >> [ 253.877983] Call Trace: >> [ 253.877983] >> [ 253.877983] __dump_stack+0x22/0x30 >> [ 253.877983] dump_stack_lvl+0x60/0x80 >> [ 253.877983] dump_stack+0x19/0x24 >> [ 253.877983] __lock_acquire+0xd3a/0x28e0 >> [ 253.877983] ? __lock_acquire+0x5a9/0x28e0 >> [ 253.877983] ? __lock_acquire+0x5a9/0x28e0 >> [ 253.877983] ? barn_get_empty_sheaf+0x1d/0xb0 >> [ 253.877983] lock_acquire+0xc3/0x270 >> [ 253.877983] ? barn_get_empty_sheaf+0x1d/0xb0 >> [ 253.877983] ? __kfree_rcu_sheaf+0x52/0x3d0 >> [ 253.877983] _raw_spin_lock_irqsave+0x47/0x70 >> [ 253.877983] ? barn_get_empty_sheaf+0x1d/0xb0 >> [ 253.877983] barn_get_empty_sheaf+0x1d/0xb0 >> [ 253.877983] ? __kfree_rcu_sheaf+0x52/0x3d0 >> [ 253.877983] __kfree_rcu_sheaf+0x19f/0x3d0 >> [ 253.877983] kvfree_call_rcu+0xaf/0x390 >> [ 253.877983] set_cpus_allowed_force+0xc8/0xf0 > > set_cpus_allowed_force() is calling kfree_rcu() with a raw spinlock > (pi_lock) held, but barn->lock is normal spinlock, lockdep prints an > error because on PREEMPT_RT normal spinlocks are converted to > sleeping locks but raw spinlocks are not. Hm right, Ulad did raise this issue and thus I made kvfree_call_rcu() skip the kfree_rcu_sheaf() attempt on CONFIG_PREEMPT_RT. But I forgot that lockdep (or a related debugging option) checks this context even with !PREEMPT_RT. We could skip kfree_rcu_sheaf() when this debugging is enabled? Not ideal. Is there a way to detect such a context on runtime and only skip kfree_rcu_sheaf() when really necessary? > Hmm... but it isn't great to convert barn->lock to > a raw spinlock just because of this? > >> [ 253.877983] ? cpuset_cpus_allowed_fallback+0x27/0x250 >> [ 253.877983] cpuset_cpus_allowed_fallback+0x15d/0x250 >> [ 253.877983] select_fallback_rq+0x1d8/0x250 >> [ 253.877983] ? __pfx___balance_push_cpu_stop+0x10/0x10 >> [ 253.877983] __balance_push_cpu_stop+0x4f/0x200 >> [ 253.877983] cpu_stopper_thread+0x147/0x210 >> [ 253.877983] ? __pfx_cpu_stopper_thread+0x10/0x10 >> [ 253.877983] smpboot_thread_fn+0x24c/0x390 >> [ 253.877983] ? __pfx_smpboot_thread_fn+0x10/0x10 >> [ 253.877983] kthread+0x1fa/0x230 >> [ 253.877983] ? __pfx_smpboot_thread_fn+0x10/0x10 >> [ 253.877983] ? __pfx_kthread+0x10/0x10 >> [ 253.877983] ret_from_fork+0x157/0x2c0 >> [ 253.877983] ? __pfx_kthread+0x10/0x10 >> [ 253.877983] ret_from_fork_asm+0x1a/0x30 >> [ 253.877983] >