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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E35B1C433F5 for ; Thu, 30 Sep 2021 12:04:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B83EA619E9 for ; Thu, 30 Sep 2021 12:04:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350639AbhI3MGf (ORCPT ); Thu, 30 Sep 2021 08:06:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350490AbhI3MGc (ORCPT ); Thu, 30 Sep 2021 08:06:32 -0400 Received: from mail-lf1-x12c.google.com (mail-lf1-x12c.google.com [IPv6:2a00:1450:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E632C06176A for ; Thu, 30 Sep 2021 05:04:49 -0700 (PDT) Received: by mail-lf1-x12c.google.com with SMTP id b15so24126761lfe.7 for ; Thu, 30 Sep 2021 05:04:49 -0700 (PDT) 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=UjgEbYgB1dUBICvlxnlZlHIbnstojizK8xPrV/3hfiU=; b=Mw5fy5Cd5FuSkEKCvXD9IxDwtLhyBdpOPgz00UTazXrMZctuiJzGTNrp8lpgTVhkQD oW7Uepf9piLCCyJslJdJ86U8PPnfNR/Juv7M4d51MRmTybBLrCNsoehE3W0sYRNxxFC2 qnM43L2+H6yg1zwNdWGQXYSbfjZ5wDO/w/KicnBV2JyZV4G9/VeUBhR3PnLLrxSIFkww mrx00ZjbEtK165HMNp7y2D14CjeaBIeILnnVtQF3j8GpRGjFy+zQ9GhjbICdhUNoAv90 ElrMv4NKkeXuFKIDj0BNuY8E75WhNgDEoV9WvHrg1gEfIinGOTVs1tcaHi3uPsrywqil ZKAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=UjgEbYgB1dUBICvlxnlZlHIbnstojizK8xPrV/3hfiU=; b=snenfYPu/PiTZjBIq9wvu772yo4vfHHqXqDQP/5jc7SI26ZmJRCcAUz3v0AGuerATb chUstr3DUQl3KGoe8iCBkGJjfdCdEvBufMCa/I9QNzz5ZXgTN2RjpOCQYm3cBqp+DeSl kVvSzrpoSbSh6iyuyOSRrTrMVEOi4LW4iot/jQXiBrJ0gKgc1QnbwdZYLYOl9pBLH8ga a1M8CRfgbTEGnAGDzhSIYmAjlgJqfSEYcZNVDDC05hahuuyUODlRUI+wuzpMxaJ/3S9z CxRsIxt/GsNhIhTXHEqEcV/lRAjLksrIYT1GSYwX73xpOPlwABG0PDhAdj4Rx8hm/+pe 0hwg== X-Gm-Message-State: AOAM532tDUxOZmvBuvTQSE6smUrX6gtke9sUR4YuOXO71m9UmyKhrVIR ItKzZgyLxYdtX5Bir3zv3U9eTu25wA9JgKxO14GLqQ== X-Google-Smtp-Source: ABdhPJw1zA/FsBBHwIphCACp2TVxErJ29YjNcxKmb8wd2yWA60DQ7TBOfEMVQcydPvMdjJTFM5zGbzLcVJ1nv16IfDI= X-Received: by 2002:a05:6512:1515:: with SMTP id bq21mr5610691lfb.71.1633003487945; Thu, 30 Sep 2021 05:04:47 -0700 (PDT) MIME-Version: 1.0 References: <20210929190549.860541-1-saravanak@google.com> In-Reply-To: <20210929190549.860541-1-saravanak@google.com> From: Ulf Hansson Date: Thu, 30 Sep 2021 14:04:11 +0200 Message-ID: Subject: Re: [PATCH v2] driver core: Reject pointless SYNC_STATE_ONLY device links To: Saravana Kannan Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Android Kernel Team , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Sept 2021 at 21:05, Saravana Kannan wrote: > > SYNC_STATE_ONLY device links intentionally allow cycles because cyclic > sync_state() dependencies are valid and necessary. > > However a SYNC_STATE_ONLY device link where the consumer and the supplier > are the same device is pointless because the device link would be deleted > as soon as the device probes (because it's also the consumer) and won't > affect when the sync_state() callback is called. It's a waste of CPU cycles > and memory to create this device link. So reject any attempts to create > such a device link. > > Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag") > Reported-by: Ulf Hansson > Signed-off-by: Saravana Kannan Reviewed-by: Ulf Hansson Kind regards Uffe > --- > v1 -> v2: > - Moved the check higher up in the function. > > drivers/base/core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 15986cc2fe5e..249da496581a 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -687,7 +687,8 @@ struct device_link *device_link_add(struct device *consumer, > { > struct device_link *link; > > - if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS || > + if (!consumer || !supplier || consumer == supplier || > + flags & ~DL_ADD_VALID_FLAGS || > (flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) || > (flags & DL_FLAG_SYNC_STATE_ONLY && > (flags & ~DL_FLAG_INFERRED) != DL_FLAG_SYNC_STATE_ONLY) || > -- > 2.33.0.685.g46640cef36-goog >