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 5458AC4332F for ; Thu, 6 Oct 2022 13:50:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231631AbiJFNuP (ORCPT ); Thu, 6 Oct 2022 09:50:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231676AbiJFNuJ (ORCPT ); Thu, 6 Oct 2022 09:50:09 -0400 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7ECC28E27 for ; Thu, 6 Oct 2022 06:49:57 -0700 (PDT) Received: by mail-pj1-x1033.google.com with SMTP id fw14so1799086pjb.3 for ; Thu, 06 Oct 2022 06:49:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=mWMJic3+3eVweR7Hb3wJwKAsDypmbh3PTgAfppiGim0=; b=ZkJ3eSSvWEQHG4zrCYO/rtAQMC+rTCblUgkXT/sojUfeAz6djcfzmaQhTE1VFhHlb5 c1atXYEjU3xEGE7hI13KaDEcIgKWkEtN1hvwHwEilxv96++sncyPLWqzhVGEXpdUs06G CdnNu3apyqKTZeVSCSOWHTmHzGnFe3F2KnJM3MWKtya9Y3YnYefumWTirYL9USS1lYub A/mEPLmhBfwN3a8nKOKM2rGPY5Mu7KrZF82KX4Ex4dyspcvVZE3FoiZPzuE8M8MOv+bw OGNw6BEO2hAZNd93A/lo5mHGoPx0ZTYnxKuuVNn8KZcYJUWz6h7H+Lqu3yOpWNU2Gh62 93nA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=mWMJic3+3eVweR7Hb3wJwKAsDypmbh3PTgAfppiGim0=; b=qh4qFs/4LQKzku6PoSLoLFTdga8SuFGUHRQm5Sfs2Z8uqFdZvxdOogAqYxO4e0TL3y QD1GIpHc6mjcjTYgKXXueLq/203PaCgnfUmNoi1eyWg4dvf1zcUzRodXUiCVzQWvgBDI Fvt8+Q1SJ3Aj1vK5tI8DPaZB4ZhiglPRPxmDpdGMx1Sb1HWedvMP6MPcOZWFl8cb2Qpz M+/wGPS+3P8HwUteXJFR1Gw2R4eYiuE90bNoKLxfbWADoGISmL54YuWB18Ddau1SFM8u TIBTHaDN3ji+X7BRJFBEsFXUvIdXg66CQF51tckngW29dVk2wMrLJhZ2pTKqfNikp4dN VLUQ== X-Gm-Message-State: ACrzQf0hfQPMHkI6uYxuZa45GHenUoAR9Xc/C1vo7dI4iI9sf2ymk2qM Mh0llHCMHmkx6FPncdyp7DXL X-Google-Smtp-Source: AMsMyM6adD7Qiz1npAI/QIQqcXzzqSFAqQ7y/8Uf2egzhAubDRgCFWLfQ2y5Xniqseks4ePMXNdkGg== X-Received: by 2002:a17:90a:4b47:b0:20a:e47c:1450 with SMTP id o7-20020a17090a4b4700b0020ae47c1450mr10742123pjl.198.1665064195847; Thu, 06 Oct 2022 06:49:55 -0700 (PDT) Received: from localhost.localdomain ([220.158.158.220]) by smtp.gmail.com with ESMTPSA id k25-20020a635a59000000b00434760ee36asm1874053pgm.16.2022.10.06.06.49.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Oct 2022 06:49:55 -0700 (PDT) From: Manivannan Sadhasivam To: kishon@kernel.org, lpieralisi@kernel.org, bhelgaas@google.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kw@linux.com, robh@kernel.org, vidyas@nvidia.com, vigneshr@ti.com, Manivannan Sadhasivam Subject: [PATCH v3 3/5] PCI: endpoint: Use a separate lock for protecting epc->pci_epf list Date: Thu, 6 Oct 2022 19:19:25 +0530 Message-Id: <20221006134927.41437-4-manivannan.sadhasivam@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221006134927.41437-1-manivannan.sadhasivam@linaro.org> References: <20221006134927.41437-1-manivannan.sadhasivam@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org The EPC controller maintains a list of EPF drivers added to it. For protecting this list against the concurrent accesses, the epc->lock (used for protecting epc_ops) has been used so far. Since there were no users trying to use epc_ops and modify the pci_epf list simultaneously, this was not an issue. But with the addition of callback mechanism for passing the events, this will be a problem. Because the pci_epf list needs to be iterated first for getting hold of the EPF driver and then the relevant event specific callback needs to be called for the driver. If the same epc->lock is used, then it will result in a deadlock scenario. For instance, ... mutex_lock(&epc->lock); list_for_each_entry(epf, &epc->pci_epf, list) { epf->event_ops->core_init(epf); | |-> pci_epc_set_bar(); | |-> mutex_lock(&epc->lock) # DEADLOCK ... So to fix this issue, use a separate lock called "list_lock" for protecting the pci_epf list against the concurrent accesses. This lock will also be used by the callback mechanism. Signed-off-by: Manivannan Sadhasivam --- drivers/pci/endpoint/pci-epc-core.c | 9 +++++---- include/linux/pci-epc.h | 2 ++ 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c index 3bc9273d0a08..6cce430d431b 100644 --- a/drivers/pci/endpoint/pci-epc-core.c +++ b/drivers/pci/endpoint/pci-epc-core.c @@ -613,7 +613,7 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf, if (type == SECONDARY_INTERFACE && epf->sec_epc) return -EBUSY; - mutex_lock(&epc->lock); + mutex_lock(&epc->list_lock); func_no = find_first_zero_bit(&epc->function_num_map, BITS_PER_LONG); if (func_no >= BITS_PER_LONG) { @@ -640,7 +640,7 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf, list_add_tail(list, &epc->pci_epf); ret: - mutex_unlock(&epc->lock); + mutex_unlock(&epc->list_lock); return ret; } @@ -672,11 +672,11 @@ void pci_epc_remove_epf(struct pci_epc *epc, struct pci_epf *epf, list = &epf->sec_epc_list; } - mutex_lock(&epc->lock); + mutex_lock(&epc->list_lock); clear_bit(func_no, &epc->function_num_map); list_del(list); epf->epc = NULL; - mutex_unlock(&epc->lock); + mutex_unlock(&epc->list_lock); } EXPORT_SYMBOL_GPL(pci_epc_remove_epf); @@ -773,6 +773,7 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops, } mutex_init(&epc->lock); + mutex_init(&epc->list_lock); INIT_LIST_HEAD(&epc->pci_epf); ATOMIC_INIT_NOTIFIER_HEAD(&epc->notifier); diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h index a48778e1a4ee..fe729dfe509b 100644 --- a/include/linux/pci-epc.h +++ b/include/linux/pci-epc.h @@ -122,6 +122,7 @@ struct pci_epc_mem { * struct pci_epc - represents the PCI EPC device * @dev: PCI EPC device * @pci_epf: list of endpoint functions present in this EPC device + * list_lock: Mutex for protecting pci_epf list * @ops: function pointers for performing endpoint operations * @windows: array of address space of the endpoint controller * @mem: first window of the endpoint controller, which corresponds to @@ -139,6 +140,7 @@ struct pci_epc_mem { struct pci_epc { struct device dev; struct list_head pci_epf; + struct mutex list_lock; const struct pci_epc_ops *ops; struct pci_epc_mem **windows; struct pci_epc_mem *mem; -- 2.25.1