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 EE7F93D7F for ; Fri, 19 May 2023 08:46:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B389C433D2; Fri, 19 May 2023 08:46:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684486008; bh=1+vFu1w66KDdvKSmhCKgDf3+NlflV3f/KylBogyLtZA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=eAPgyDZkkfi7AME2UlGyWvUsDZGIN7nB1jVJg2mfrc8IIwnUhF8KmkQtEqOnK5c8E 5RQWhptxAtp/caeHPNAfH0M8YP/rWKVXQbEbPAZXislGlnrqD2ibXrniKaC2ZRVR2j O5LlEwyVdGQheA4lmprtSSw642v7Lt2pnxoOfCX5KMLDQ5MiowMI55CiR+jzNFP1Vv KYbW0LxSxgmngc0E/1Vtji1CHI3XhDZRR8GsH7hqGLrwSHxdcV3U4eKV7Kdl0OnglF Q/DI/nFNQCUADdjNcRoay6VkSNXMoHbVsEjxvgnLDyjrvGQlVFjkk/QhvmWidoYVeg RhFMgobwoERlA== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1pzvl8-00GMgT-7g; Fri, 19 May 2023 09:46:46 +0100 Date: Fri, 19 May 2023 09:46:45 +0100 Message-ID: <86cz2wlnd6.wl-maz@kernel.org> From: Marc Zyngier To: Jean-Philippe Brucker Cc: oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [PATCH 0/4] KVM: arm64: vgic: Locking fixes In-Reply-To: <20230518100914.2837292-1-jean-philippe@linaro.org> References: <20230518100914.2837292-1-jean-philippe@linaro.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: jean-philippe@linaro.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Thu, 18 May 2023 11:09:14 +0100, Jean-Philippe Brucker wrote: > > Another fun locking puzzle, between the new config_lock and srcu. > Patch 1 attempts to fix it, and the other patches fix simpler issues. Thanks for that and for your excellent description of the problems. > I got these lockdep reports while running KVM QEMU on a TCG QEMU, but it > can also be triggered by running the vgic_irq kselftest on TCG QEMU. > Now, with the fix and lockdep enabled, vgic_irq hangs but I believe it's > an unrelated weirdness: if I introduce a separate lockdep warning for > some made up locks, then the test passes again. So I'm sending this out > now for discussion, and will investigate that one later. I've taken these patches for a spin, and I cannot reproduce this hang, though I'm running on actual HW and not QEMU. It would be really annoying if lockdep actively introduced issues... :-/ Any chance you could dig into this as you have a good reproducer? I'll try to setup a TGC environment on my end as well. Thanks, M. -- Without deviation from the norm, progress is not possible.