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 AD011346E46 for ; Fri, 1 May 2026 19:37:23 +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=1777664243; cv=none; b=VHSQEYjMv2kwXzQ8UPmz1pqlQ759iyCxZah3CAJN33UsoimZmmIMm2NHym9Fkupz0aHAVGSHk/MZwuT7R2krZ6gLIr178ZUhsI4a5qWsP9Ml2gp5ZymZ8d4vkQndP9YzukoFECtL6AVYdqc5MkK+TXrpniBrw/qLff8JGrJ1HKY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777664243; c=relaxed/simple; bh=a1HVvxBli67IFW2LWFabcWygSyAIX9i8lmA4uyxDfZo=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=C2s2fyWtcOezqGBBFnWuN26QBbJr7SMj/tvZayEHhgbvxKWCYFcM+c3IgwY85TwCdm7Ngpv3OHHoDjJ7sq5CC3RRrn59Y+es0fwMonNdI8O6/JZ0SZEdvQz7q09qyuJufdpCWs9adM5wwVxsQejrOAaU2eRG7EycftHaRBqM2WQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XRrKsHd0; 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="XRrKsHd0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F1BBC2BCB4; Fri, 1 May 2026 19:37:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777664243; bh=a1HVvxBli67IFW2LWFabcWygSyAIX9i8lmA4uyxDfZo=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=XRrKsHd0k7kTGf+plnf/j0Dw2fiTN/KOiqASjs7GWJmzgoteNrbKOxfloY/xo4BAb o45r277c1Ge6mRg+8t4nJdkxx+Extujj1nsOxKc+EngKnoJLDUgq43ub4ynp++Aar6 1PJWl48QaN9DDs/rTDTsyFQylcWI3qjjE8M/Em83424mhfa2rvoJkiAajegC3l8vfs E1NoFiKmRbNOAXEbndBWyGCIqrJu++Ii8vMApxX0eSzlbZKVHk9U1KDUYRcIZrsFPu i6OsttY0soEidqXOyRrUo8j99fs2Qd8TYWfSmHR4x+II3lGOJDizlYaICdimfuyvV2 nc5dm1aKpjh4Q== Date: Fri, 1 May 2026 14:37:21 -0500 From: Bjorn Helgaas To: Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= Cc: Bjorn Helgaas , Manivannan Sadhasivam , Lorenzo Pieralisi , Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Lukas Wunner , Shuan He , linux-pci@vger.kernel.org Subject: Re: [PATCH] PCI/proc: Fix race between pci_proc_init() and pci_bus_add_device() Message-ID: <20260501193721.GA511830@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260501010127.GA990551@rocinante> On Fri, May 01, 2026 at 10:22:56AM +0900, Krzysztof Wilczyński wrote: > Hello, > > > Thus, wrap the for_each_pci_dev() loop with pci_lock_rescan_remove() to > > serialise against concurrent PCI bus operations. Add an early return in > > pci_proc_attach_device() when dev->procent is already set, making the > > function idempotent and symmetric with pci_proc_detach_device() which > > clears this field. > > A note on testing: > > 0-day bot (recent test runs; newer builds will arrive later): > - https://lore.kernel.org/linux-pci/202603162306.2oKy0qcP-lkp@intel.com > > Sashiko's feedback: > - https://sashiko.dev/#/patchset/20260430003542.455198-1-kwilczynski%40kernel.org > > Lorenzo Pieralisi did some testing reported outside the mailing list (we > talked on IRC) on the platform he had some boot issues. With this patch > applied, the problems seen before were resolved. Thanks! Can we include a link to the problem report and maybe a couple lines of the symptoms? Also the analysis of Sashiko feedback? Sashiko worried about pci_lock_rescan_remove() deadlock between pci_proc_init() and PCI controller drivers with async probing. pci_proc_init() is a device initcall. Some drivers are also device initcalls (imx_pcie_init(), ks_pcie_init(), rcar_pcie_init()), and it looks like they can use async probing. Does this rely on the pci_proc_init() device_initcall happening before any of the driver device_initcalls? That would be non-obvious and fragile. The second sashiko issue (concurrent calls of pci_proc_attach_device()) also seems worth a look. The pci_enable_sriov() path isn't serialized by pci_lock_rescan_remove(): pci_enable_sriov sriov_enable sriov_add_vfs pci_iov_add_virtfn pci_bus_add_device pci_proc_attach_device bus->procdir = proc_mkdir() If two threads race for devices on the same bus, it looks like the loser can set bus->procdir back to NULL when proc_mkdir() fails with "duplicate entry". This is a per-device path, but we're creating a per-bus directory. I wonder if that proc_mkdir() could/should be done in a bus creation path?