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=-4.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED 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 75889C282C4 for ; Tue, 12 Feb 2019 16:18:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4303F21773 for ; Tue, 12 Feb 2019 16:18:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="W7V1pm8o" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731016AbfBLQSQ (ORCPT ); Tue, 12 Feb 2019 11:18:16 -0500 Received: from mail-ua1-f67.google.com ([209.85.222.67]:41572 "EHLO mail-ua1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729355AbfBLQSQ (ORCPT ); Tue, 12 Feb 2019 11:18:16 -0500 Received: by mail-ua1-f67.google.com with SMTP id z24so1063561ual.8 for ; Tue, 12 Feb 2019 08:18:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=E6BeYoUof4NqQsXGBR7kWHKIfxXRI0fl6tbuor8qNFs=; b=W7V1pm8oOKlhebGMV2gGKcKJzcwZ1SnZcY4IKn1GB/qTenfos8XWuWeC9tmdQ7IH2F VqqeO6B7W9LqnzJdVsltSyesUY4UjGDJAuLRDGjVP3snipsFwPREFHQHV/g9JGp2fShV Ksu+osUnD3NWLhKhrUxTmsng8JjMgi0n+OgoFfjzLOXqYQy0o6aCjpj4EEshN86+LnPz 0YU1lj0q4ApLQBJggP3H61eG4r+IY7IuMwSxhJOe5rlAwfnwa6phdvHpwJY4a1HMbBrx VvuqvmaDWjCk02/1ejOOeb/cmZJqVRAesNehOWvZ4nUKClsoi9tjvFSUa3nfO05k4q/C zSqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=E6BeYoUof4NqQsXGBR7kWHKIfxXRI0fl6tbuor8qNFs=; b=pF/U3tkzdEDx4dMxepW7LCRJ/OfOpt59yrJBhcdQS+O+36T03Rj/ONj6SNv7lI5U+5 kh9VtbImm1KO+NMOpkjFab+umJoGeRv+8SmxP4MFCWKU5im6OckoHBsThvpOtPjbPzYV Nk3rIU3oCcQIiCNfKnDf5e/cps9GT8/InH8qK4v+UmUdpw1uQrcFaopsPBZvZ63mwMVs eDiFtVq1EBc4dICAMN3dD8pSlwiS72s6IrsLKpmJMvrdXWNkNemj5w8SzekbiQgdKvxE AsWNBTIa+v2epJcs8tv/u8gvAdOg5rAPT/pgKqStTdIT4vzH78iVMbhXXksSnvtAsfwa xMOw== X-Gm-Message-State: AHQUAuZwngWAnPJ7XIEKLQIYeiqw5iFj9QAMV++txF/6FK0tJk9/fDvc SkWW5pfLnCGXaF6iJoKfBdx0kppuxDbiqufLCmlRQ0UVBB4= X-Google-Smtp-Source: AHgI3IYh7Aay9pz4AtbO8CAuJwJ8zfzstDUwabBmJX9OrWp5C8krRhsz98R5xhE+2453PjwHbI1kYGrG8hTf4hcB2Fo= X-Received: by 2002:ab0:270b:: with SMTP id s11mr1823391uao.25.1549988295160; Tue, 12 Feb 2019 08:18:15 -0800 (PST) MIME-Version: 1.0 References: <5510642.nRbR3bcduN@aspire.rjw.lan> <1670239.00ZbddH1IV@aspire.rjw.lan> In-Reply-To: <1670239.00ZbddH1IV@aspire.rjw.lan> From: Ulf Hansson Date: Tue, 12 Feb 2019 17:17:39 +0100 Message-ID: Subject: Re: [PATCH 1/2] PM-runtime: Fix __pm_runtime_set_status() race with runtime resume To: "Rafael J. Wysocki" Cc: Greg Kroah-Hartman , LKML , Linux PM , Daniel Vetter , Lukas Wunner , Andrzej Hajda , Russell King - ARM Linux , Lucas Stach , Linus Walleij , Thierry Reding , Laurent Pinchart , Marek Szyprowski Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Feb 2019 at 13:10, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki > > Commit 4080ab083000 ("PM-runtime: Take suppliers into account in > __pm_runtime_set_status()") introduced a race condition that may > trigger if __pm_runtime_set_status() is used incorrectly (that is, > if it is called when PM-runtime is enabled for the target device > and working). > > In that case, if the original PM-runtime status of the device is > RPM_SUSPENDED, a runtime resume of the device may occur after > __pm_runtime_set_status() has dropped its power.lock spinlock > and before deactivating its suppliers, so the suppliers may be > deactivated while the device is PM-runtime-active which may lead > to functional issues. > > To avoid that, modify __pm_runtime_set_status() to check whether > or not PM-runtime is enabled for the device before activating its > suppliers (if the new status is RPM_ACTIVE) and either return an > error if that's the case or increment the device's disable_depth > counter to prevent PM-runtime from being enabled for it while > the remaining part of the function is running (disable_depth is > then decremented on the way out). > > Fixes: 4080ab083000 ("PM-runtime: Take suppliers into account in __pm_runtime_set_status()") > Signed-off-by: Rafael J. Wysocki > --- > drivers/base/power/runtime.c | 24 ++++++++++++++++++------ > 1 file changed, 18 insertions(+), 6 deletions(-) > > Index: linux-pm/drivers/base/power/runtime.c > =================================================================== > --- linux-pm.orig/drivers/base/power/runtime.c > +++ linux-pm/drivers/base/power/runtime.c > @@ -1129,6 +1129,22 @@ int __pm_runtime_set_status(struct devic > if (status != RPM_ACTIVE && status != RPM_SUSPENDED) > return -EINVAL; > > + spin_lock_irq(&dev->power.lock); > + > + /* > + * Prevent PM-runtime from being enabled for the device or return an > + * error if it is enabled already and working. > + */ > + if (dev->power.runtime_error || dev->power.disable_depth) > + dev->power.disable_depth++; > + else > + error = -EAGAIN; > + > + spin_unlock_irq(&dev->power.lock); > + > + if (error) > + return error; > + > /* > * If the new status is RPM_ACTIVE, the suppliers can be activated > * upfront regardless of the current status, because next time > @@ -1147,12 +1163,6 @@ int __pm_runtime_set_status(struct devic > > spin_lock_irq(&dev->power.lock); > > - if (!dev->power.runtime_error && !dev->power.disable_depth) { > - status = dev->power.runtime_status; > - error = -EAGAIN; > - goto out; > - } > - > if (dev->power.runtime_status == status || !parent) > goto out_set; > > @@ -1205,6 +1215,8 @@ int __pm_runtime_set_status(struct devic > device_links_read_unlock(idx); > } > > + pm_runtime_enable(dev); pm_runtime_enable() uses spin_lock_irqsave(), rather than spin_lock_irq() - is there a reason to why you want to allow that here, but not earlier in the function? > + > return error; > } > EXPORT_SYMBOL_GPL(__pm_runtime_set_status); > Other than the above comment, this looks good to me. Kind regards Uffe