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 X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C75ADC5ACD3 for ; Wed, 11 Mar 2020 23:14:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDE0820751 for ; Wed, 11 Mar 2020 23:14:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="B7/KZHMf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731562AbgCKXOa (ORCPT ); Wed, 11 Mar 2020 19:14:30 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:42901 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731512AbgCKXOW (ORCPT ); Wed, 11 Mar 2020 19:14:22 -0400 Received: by mail-pl1-f194.google.com with SMTP id t3so1816683plz.9 for ; Wed, 11 Mar 2020 16:14:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=3xshg7ExKoZEQ1cmRMbwPGjLTkGkDqXFoENhWmw2kvw=; b=B7/KZHMfx/pmxw43ZXgtosczRo5w1B5pV4DwD4I7ocTJtH/KHnLq5kPOgKQIwkyF2W eAYNB5zzBdc1/Ow+NeqHY/wrbNlnUfUt4OLrGRyGiCDBdwW/SzD8W6WKyk6ADh36204z KoRbmp5/BFJPsG3fxhNoK/HnTXDX3Cve4EjkU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=3xshg7ExKoZEQ1cmRMbwPGjLTkGkDqXFoENhWmw2kvw=; b=N/TWcPY+ZjdHRvUsuCJ41X5GM/UNkOoW0CPgre31i5L/RmC+K7fpt7Htd2WsAQkhpJ jZYesLgrf69MqDhnlKdi9YNKcHtp+WEyOn3mgcnpOt+d3ILKafHp0MVY0FwXQgHn6JGR DxuEQADwmC15FOUooxQPFkVXQF0dz4c99GCsA5oPTft8NJoom2JzTCnsZVswmaPv3WZr djqUhZycpJOgz9RTHeIdiE618BksC8HfOHu4dp+KxA5lXuLxlUCUM+KBh82i892vQ5mD f5BWSKAQHZvWvxMscvKDUhMhIIKedDZX3kVtKGkYvn5dqwGxiRIvxCYIednQuUQYgChy qfWA== X-Gm-Message-State: ANhLgQ0EAdBwyNczkRe8ZC4BX5sHsOsm5WUAFaNBAOx6rt/8erCIfl5X cbX/0Pdogzri+UDBatxldm2eoQ== X-Google-Smtp-Source: ADFU+vtJPb7raHtNVcBlj/4DXcl6eXZsrwxmV0Q1tUcIzYLc0r3sj7CGDQOd1wc55wtMz5uc24ug5Q== X-Received: by 2002:a17:90a:de16:: with SMTP id m22mr1086840pjv.142.1583968461826; Wed, 11 Mar 2020 16:14:21 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id g75sm2606334pje.37.2020.03.11.16.14.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2020 16:14:21 -0700 (PDT) From: Douglas Anderson To: Andy Gross , Bjorn Andersson , Maulik Shah Cc: mka@chromium.org, Rajendra Nayak , evgreen@chromium.org, Lina Iyer , swboyd@chromium.org, Douglas Anderson , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFT PATCH v2 08/10] drivers: qcom: rpmh-rsc: spin_lock_irqsave() for tcs_invalidate() Date: Wed, 11 Mar 2020 16:13:46 -0700 Message-Id: <20200311161104.RFT.v2.8.I07c1f70e0e8f2dc0004bd38970b4e258acdc773e@changeid> X-Mailer: git-send-email 2.25.1.481.gfbce0eb801-goog In-Reply-To: <20200311231348.129254-1-dianders@chromium.org> References: <20200311231348.129254-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Auditing tcs_invalidate() made me worried. Specifically I saw that it used spin_lock(), not spin_lock_irqsave(). That always worries me. As I understand it, using spin_lock() is only valid in these situations: a) You know you are running in the interrupt handler (and all other users of the lock use the "irqsave" variant). b) You know that nobody using the lock is ever running in the interrupt handler. c) You know that someone else has always disabled interrupts before your code runs and thus the "irqsave" variant is pointless. >From auditing the driver we look OK. ...except that there is one further corner case. If sometimes your code is called with IRQs disabled and sometimes it's not you will get in trouble if someone ever boots your board with "nosmp" (AKA in uniprocessor mode). In such a case if someone else has the lock (without disabling interrupts) and they get swapped out then your code (with interrupts disabled) might loop forever waiting for the spinlock. It's just safer to use the irqsave version, so let's do that. In future patches I believe tcs_invalidate() will always be called with interrupts off anyway. Signed-off-by: Douglas Anderson --- Changes in v2: None drivers/soc/qcom/rpmh-rsc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c index ba489d18c20e..c82c734788b1 100644 --- a/drivers/soc/qcom/rpmh-rsc.c +++ b/drivers/soc/qcom/rpmh-rsc.c @@ -218,9 +218,10 @@ static bool tcs_is_free(struct rsc_drv *drv, int tcs_id) static int tcs_invalidate(struct rsc_drv *drv, int type) { int m; + unsigned long flags; struct tcs_group *tcs = &drv->tcs[type]; - spin_lock(&tcs->lock); + spin_lock_irqsave(&tcs->lock, flags); if (bitmap_empty(tcs->slots, MAX_TCS_SLOTS)) { spin_unlock(&tcs->lock); return 0; @@ -235,7 +236,7 @@ static int tcs_invalidate(struct rsc_drv *drv, int type) write_tcs_reg_sync(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, m, 0); } bitmap_zero(tcs->slots, MAX_TCS_SLOTS); - spin_unlock(&tcs->lock); + spin_unlock_irqrestore(&tcs->lock, flags); return 0; } -- 2.25.1.481.gfbce0eb801-goog