From nobody Wed Apr 8 14:47:55 2026 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 EC2FFC6FA83 for ; Sat, 10 Sep 2022 09:05:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229565AbiIJJFf (ORCPT ); Sat, 10 Sep 2022 05:05:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229552AbiIJJFa (ORCPT ); Sat, 10 Sep 2022 05:05:30 -0400 Received: from mail-wr1-x434.google.com (mail-wr1-x434.google.com [IPv6:2a00:1450:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDB0C5C950 for ; Sat, 10 Sep 2022 02:05:28 -0700 (PDT) Received: by mail-wr1-x434.google.com with SMTP id c11so6938700wrp.11 for ; Sat, 10 Sep 2022 02:05:28 -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=XZ9bImxf8XtKwz5O25eFDJyl1TKgS+4Hi4wWwjJENYHZOY29lP2VbpTwYOMWw++olk 4K1qpSSO4+87Hd6R+l2+0U0FqICl6zqzF0GSBh84YzSC4whAlP/MdFl21okuGN10B6Yh Sn8/q4/61ZcdlRKw4yjYBQnjgt0naNiZCApDprcpVXwF25huetUS/7ok5KdCu0Ty+J/Z cu6jV5yEoGommBEYZlut/agcSalGVwtlTwIp5k4KkI8gewIAZVYazi0bOSNUFSn0sWqx zaSSgaqEqKUC8EgGhwXOKIDrdGQSdyYn+ywLMVk5Ap0P19n4IkEEy0TnDVBdAaQxa9vd GQSA== 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=1iAB+ZfUWY0GU/31V105XQbLRw9kVkCl3CtWLFtaOX+fNNXKlVXqLeGP5/uVSVVw4H XY6xFO0KRGNfYgMFxbt25ASoBqRHn/U9tihRDjwWQ3HEpP/2rdkEppWJgxcJSBwAHUe5 LISOw4r6WqU+9Oed9QcA/FlUFUzdQhovVcm0v7gPz6gfOBgqUqFA6Oqrs7g2t34+Fnup S0wl2sHZW8Fj75hegJUhVxPJFvr6Kh5PPEww2/jfk0C2rskrcaBOakOCrt3IfqStHWc2 UYoOtFgmdlViCBQdpASbV6RRlnGduIUsf1CZwMPV1paKsrPkQ0cS7kK02R6rSUaVxyZ+ sptA== X-Gm-Message-State: ACgBeo2sJAj5o/EdaI3KGVkIw597D1/smYD3SogR5vayIsCZH965ST/g VHgpduEAVgpGNcICGg+x47ZW X-Google-Smtp-Source: AA6agR6JF41rR8QPL5xWtDvgTWZqQ98E41/qIkwxUXbocZyQdJPUfyiZPLyuHGg3ZwaAWUEH25O4Aw== X-Received: by 2002:a05:6000:1245:b0:228:6aa7:dbb2 with SMTP id j5-20020a056000124500b002286aa7dbb2mr10485053wrx.77.1662800727504; Sat, 10 Sep 2022 02:05:27 -0700 (PDT) Received: from localhost.localdomain ([117.217.182.47]) by smtp.gmail.com with ESMTPSA id i81-20020a1c3b54000000b003a8418ee646sm3081677wma.12.2022.09.10.02.05.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Sep 2022 02:05:27 -0700 (PDT) From: Manivannan Sadhasivam To: kishon@ti.com, lpieralisi@kernel.org, bhelgaas@google.com Cc: kw@linux.com, robh@kernel.org, vidyas@nvidia.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Manivannan Sadhasivam Subject: [PATCH v2 1/3] PCI: endpoint: Use a separate lock for protecting epc->pci_epf list Date: Sat, 10 Sep 2022 14:35:06 +0530 Message-Id: <20220910090508.61157-2-manivannan.sadhasivam@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220910090508.61157-1-manivannan.sadhasivam@linaro.org> References: <20220910090508.61157-1-manivannan.sadhasivam@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 =3D=3D SECONDARY_INTERFACE && epf->sec_epc) return -EBUSY; =20 - mutex_lock(&epc->lock); + mutex_lock(&epc->list_lock); func_no =3D find_first_zero_bit(&epc->function_num_map, BITS_PER_LONG); if (func_no >=3D BITS_PER_LONG) { @@ -640,7 +640,7 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf= *epf, =20 list_add_tail(list, &epc->pci_epf); ret: - mutex_unlock(&epc->lock); + mutex_unlock(&epc->list_lock); =20 return ret; } @@ -672,11 +672,11 @@ void pci_epc_remove_epf(struct pci_epc *epc, struct p= ci_epf *epf, list =3D &epf->sec_epc_list; } =20 - mutex_lock(&epc->lock); + mutex_lock(&epc->list_lock); clear_bit(func_no, &epc->function_num_map); list_del(list); epf->epc =3D NULL; - mutex_unlock(&epc->lock); + mutex_unlock(&epc->list_lock); } EXPORT_SYMBOL_GPL(pci_epc_remove_epf); =20 @@ -773,6 +773,7 @@ __pci_epc_create(struct device *dev, const struct pci_e= pc_ops *ops, } =20 mutex_init(&epc->lock); + mutex_init(&epc->list_lock); INIT_LIST_HEAD(&epc->pci_epf); ATOMIC_INIT_NOTIFIER_HEAD(&epc->notifier); =20 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; --=20 2.25.1