From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 603281BD9EA; Wed, 30 Oct 2024 23:11:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730329860; cv=none; b=AYvxQgJf2xkOb5Ao7KlW44Qm7F0vsaF415o78tdWnk1bvOmVHuY349Ooyy6D1TUJtolZWi8f+r51AIVJ+XIO/L+u7OJ9X3Rrqp1AmtaBycT+1OAdcFXgRvZe+RxiuDbOb5Gxnn6UlW2OBZmwGXr4X8gKgJpuPIv6X6rm4eknA5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730329860; c=relaxed/simple; bh=NobT7qYPgQUDHyh4P5cTe3irZqg7DEUQJbR+GUeX5ac=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Icr2CowZgCn6Ho9gK/hkXyNfw2Z3kApIAeYd+ia3iygb7Y951T3Wshlstanni7nK6Zqv3d4KwUsUyobQkMv1/5oP98QxJiymTzLgn1jAFtmvwRnf+lQux2vUOhGzGg5ILk6cXMW4rPo2aZP40RVAh+Ld6y+JLT5SwOWGCycEN7A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VopkGahq; 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="VopkGahq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBEFCC4CECE; Wed, 30 Oct 2024 23:10:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730329860; bh=NobT7qYPgQUDHyh4P5cTe3irZqg7DEUQJbR+GUeX5ac=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=VopkGahqXCNlTpf7AI+7gIpoBrYuq5ssZSU6uX7UiPnzc+PKC3X1lD6A0oOUF1hTG atTVsEIE4NoncDheeKu3q6HeLfIqW42kgs2C6u6hsNiKRcfBN9BLc1N7YNSIIZrx/b lIA25iKdM8Lx9H6QByYehMSl4DlZReZ1aHCd5u6pjCju1Jq80p4ic5TDonx53vZQ4A 4TXtwICbCJn2D0sjy2ALwSr61qLqhpP1D4ZCXseKUEBRwyhmUHGdV4TFQuKMQ0OAfI QG2Bj/OP+4xoLAapTH//iQaowQ+XgHS1tODxxNrnV1ecO1j/92QCCYMBrWczW+SnAN k7JPIztZkQOnw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 82F26CE0864; Wed, 30 Oct 2024 16:10:58 -0700 (PDT) Date: Wed, 30 Oct 2024 16:10:58 -0700 From: "Paul E. McKenney" To: Marco Elver Cc: Vlastimil Babka , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, sfr@canb.auug.org.au, bigeasy@linutronix.de, longman@redhat.com, boqun.feng@gmail.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Subject: Re: [BUG] -next lockdep invalid wait context Message-ID: <66a745bb-d381-471c-aeee-3800a504f87d@paulmck-laptop> Reply-To: paulmck@kernel.org References: <41619255-cdc2-4573-a360-7794fc3614f7@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-next@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Oct 30, 2024 at 11:34:08PM +0100, Marco Elver wrote: > On Wed, Oct 30, 2024 at 10:48PM +0100, Vlastimil Babka wrote: > > On 10/30/24 22:05, Paul E. McKenney wrote: > > > Hello! > > > > Hi! > > > > > The next-20241030 release gets the splat shown below when running > > > scftorture in a preemptible kernel. This bisects to this commit: > > > > > > 560af5dc839e ("lockdep: Enable PROVE_RAW_LOCK_NESTING with PROVE_LOCKING") > > > > > > Except that all this is doing is enabling lockdep to find the problem. > > > > > > The obvious way to fix this is to make the kmem_cache structure's > > > cpu_slab field's ->lock be a raw spinlock, but this might not be what > > > we want for real-time response. > > > > But it's a local_lock, not spinlock and it's doing local_lock_irqsave(). I'm > > confused what's happening here, the code has been like this for years now. > > > > > This can be reproduced deterministically as follows: > > > > > > tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration 2 --configs PREEMPT --kconfig CONFIG_NR_CPUS=64 --memory 7G --trust-make --kasan --bootargs "scftorture.nthreads=64 torture.disable_onoff_at_boot csdlock_debug=1" > > > > > > I doubt that the number of CPUs or amount of memory makes any difference, > > > but that is what I used. > > > > > > Thoughts? > > > > > > Thanx, Paul > > > > > > ------------------------------------------------------------------------ > > > > > > [ 35.659746] ============================= > > > [ 35.659746] [ BUG: Invalid wait context ] > > > [ 35.659746] 6.12.0-rc5-next-20241029 #57233 Not tainted > > > [ 35.659746] ----------------------------- > > > [ 35.659746] swapper/37/0 is trying to lock: > > > [ 35.659746] ffff8881ff4bf2f0 (&c->lock){....}-{3:3}, at: put_cpu_partial+0x49/0x1b0 > > > [ 35.659746] other info that might help us debug this: > > > [ 35.659746] context-{2:2} > > > [ 35.659746] no locks held by swapper/37/0. > > > [ 35.659746] stack backtrace: > > > [ 35.659746] CPU: 37 UID: 0 PID: 0 Comm: swapper/37 Not tainted 6.12.0-rc5-next-20241029 #57233 > > > [ 35.659746] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 > > > [ 35.659746] Call Trace: > > > [ 35.659746] > > > [ 35.659746] dump_stack_lvl+0x68/0xa0 > > > [ 35.659746] __lock_acquire+0x8fd/0x3b90 > > > [ 35.659746] ? start_secondary+0x113/0x210 > > > [ 35.659746] ? __pfx___lock_acquire+0x10/0x10 > > > [ 35.659746] ? __pfx___lock_acquire+0x10/0x10 > > > [ 35.659746] ? __pfx___lock_acquire+0x10/0x10 > > > [ 35.659746] ? __pfx___lock_acquire+0x10/0x10 > > > [ 35.659746] lock_acquire+0x19b/0x520 > > > [ 35.659746] ? put_cpu_partial+0x49/0x1b0 > > > [ 35.659746] ? __pfx_lock_acquire+0x10/0x10 > > > [ 35.659746] ? __pfx_lock_release+0x10/0x10 > > > [ 35.659746] ? lock_release+0x20f/0x6f0 > > > [ 35.659746] ? __pfx_lock_release+0x10/0x10 > > > [ 35.659746] ? lock_release+0x20f/0x6f0 > > > [ 35.659746] ? kasan_save_track+0x14/0x30 > > > [ 35.659746] put_cpu_partial+0x52/0x1b0 > > > [ 35.659746] ? put_cpu_partial+0x49/0x1b0 > > > [ 35.659746] ? __pfx_scf_handler_1+0x10/0x10 > > > [ 35.659746] __flush_smp_call_function_queue+0x2d2/0x600 > > > > How did we even get to put_cpu_partial directly from flushing smp calls? > > SLUB doesn't use them, it uses queue_work_on)_ for flushing and that > > flushing doesn't involve put_cpu_partial() AFAIK. > > > > I think only slab allocation or free can lead to put_cpu_partial() that > > would mean the backtrace is missing something. And that somebody does a slab > > alloc/free from a smp callback, which I'd then assume isn't allowed? > > Tail-call optimization is hiding the caller. Compiling with > -fno-optimize-sibling-calls exposes the caller. This gives the full > picture: > > [ 40.321505] ============================= > [ 40.322711] [ BUG: Invalid wait context ] > [ 40.323927] 6.12.0-rc5-next-20241030-dirty #4 Not tainted > [ 40.325502] ----------------------------- > [ 40.326653] cpuhp/47/253 is trying to lock: > [ 40.327869] ffff8881ff9bf2f0 (&c->lock){....}-{3:3}, at: put_cpu_partial+0x48/0x1a0 > [ 40.330081] other info that might help us debug this: > [ 40.331540] context-{2:2} > [ 40.332305] 3 locks held by cpuhp/47/253: > [ 40.333468] #0: ffffffffae6e6910 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0xe0/0x590 > [ 40.336048] #1: ffffffffae6e9060 (cpuhp_state-down){+.+.}-{0:0}, at: cpuhp_thread_fun+0xe0/0x590 > [ 40.338607] #2: ffff8881002a6948 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_remove_by_name_ns+0x78/0x100 > [ 40.341454] stack backtrace: > [ 40.342291] CPU: 47 UID: 0 PID: 253 Comm: cpuhp/47 Not tainted 6.12.0-rc5-next-20241030-dirty #4 > [ 40.344807] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 40.347482] Call Trace: > [ 40.348199] > [ 40.348827] dump_stack_lvl+0x6b/0xa0 > [ 40.349899] dump_stack+0x10/0x20 > [ 40.350850] __lock_acquire+0x900/0x4010 > [ 40.360290] lock_acquire+0x191/0x4f0 > [ 40.364850] put_cpu_partial+0x51/0x1a0 > [ 40.368341] scf_handler+0x1bd/0x290 > [ 40.370590] scf_handler_1+0x4e/0xb0 > [ 40.371630] __flush_smp_call_function_queue+0x2dd/0x600 > [ 40.373142] generic_smp_call_function_single_interrupt+0xe/0x20 > [ 40.374801] __sysvec_call_function_single+0x50/0x280 > [ 40.376214] sysvec_call_function_single+0x6c/0x80 > [ 40.377543] > [ 40.378142] > > And scf_handler does indeed tail-call kfree: > > static void scf_handler(void *scfc_in) > { > [...] > } else { > kfree(scfcp); > } > } So I need to avoid calling kfree() within an smp_call_function() handler? Thanx, Paul