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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DB96AC41513 for ; Tue, 17 Oct 2023 08:30:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yjjwxV+8KcoBs1v1BdAtGBnX9w5KZPPalaFNB4gClCY=; b=jTFAP3KLrLsen0 Zt43W5GSH9i8D8OycIsZYVYyC7oJJjHMvUrt4bruxrwuNg2XTlBvgRVAYitI1X2ieWV4jAEwoYUwU 4CZDHaN5KVCoex9i9+FqWzt3TlR/Xu366x6lGujdHEep1vjYdJ+x5MYGn0D0Op8GC17CwyHJrgvwG wwHkBoXfvSvbG0w58z8fduw4RDCtUiRbx8DZC2xVRc0umN7he+Q6UqQsJzRXCglJe6NSTo83GntNW LUChEllQ9S/icK1HwVUfmoIjGhF2M6ipq7V6ptPCtTOcqfThwtDK9fv5slsWuUGgaj4z7wHZUXqnt bK9scfVvNi1DmBeDs50Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qsfSv-00BgRC-0O; Tue, 17 Oct 2023 08:30:13 +0000 Received: from mail-yb1-xb36.google.com ([2607:f8b0:4864:20::b36]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qsfSs-00BgQL-2G for linux-arm-kernel@lists.infradead.org; Tue, 17 Oct 2023 08:30:12 +0000 Received: by mail-yb1-xb36.google.com with SMTP id 3f1490d57ef6-d9a6b21d1daso6334001276.3 for ; Tue, 17 Oct 2023 01:30:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1697531409; x=1698136209; darn=lists.infradead.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=pxbU8VQAzmkVOhUJ/7DgKFkqpOThGFGr8nSN0CTJbY4=; b=Eg6nKwsdaidWf3zhKk2oLpPte7kssJ/Bzq8ElxJ1e8aUbrSRwJgC4qYwcNMrbYa2qG 4Rc9cAYmzmVemrUoylymhgZRi16Rr7Z1TIndtSGG+ehxTp3qplOdWzDO1qbW/XJWYd0g udFx7ZmuSWBoB1GLvhY/4o6MRRfSzUQH1W0c7/lLK5wLQl5qqpGZVCCIeWHU4P0QKXId QrAM7JdamqjiW4qYRx62PReP/3wDmID1+2Tl89S5H76fz6zLIbUfziXu2L7No4l90eAz 6QooXKW+4p3zGJpifmwf0Lb9d3bjMW+ooVWLTaAoJoCHe4QltG8mZL1lTjF/UWp4sdK+ n+Qg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697531409; x=1698136209; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=pxbU8VQAzmkVOhUJ/7DgKFkqpOThGFGr8nSN0CTJbY4=; b=L+IXqmDeM2MVk9kSzfkm6xKzYi4ndKwZIUTtNgiG/0hfnFrAXAlO+yONgnBFUAa+fO 0BW8/SM1qh/B3tofQEK7vPj+UZ3lgOCKPWRxQ6aJNYw9/Y7pE62xYTvMIdAmWpz1ZMg9 deFet3wPVmmy62UJ8L9BTl9j04JuPdxuEPmNIcMlzUhnalyEiIOsvUBG6vg/4MLnOlMD HB5mWtHp3War7aHul/sOrB0lAblg8isltzfTer3FGudOJNcW9EciM6A5DF79QwpZhBTX rjjfajir+NQQ+zVHZNlsBASCoSvqLfvUyG86cb5FCroqXZiRLwRfjfprjtwvqO5tzuKk /M9Q== X-Gm-Message-State: AOJu0Yx9i8IliTnUmZZ7f7SZbLxZTstKC4EooIILCk7ojeqxw2yiK2TB Gfqh4XviTSCW+/6lszDdqqA9tfMZn2d0465dwgAc9w== X-Google-Smtp-Source: AGHT+IEhYw5vI8pIZ4Y+FmCEilr+oOi7vQDFhZ/yqPSm9KF5E2p07D7Nyqk7el4fXcpUTBJRXNslGLpwa9JQAvj97Fo= X-Received: by 2002:a25:8a92:0:b0:d9a:bbe1:1b7a with SMTP id h18-20020a258a92000000b00d9abbe11b7amr1291030ybl.50.1697531409028; Tue, 17 Oct 2023 01:30:09 -0700 (PDT) MIME-Version: 1.0 References: <20230828192507.117334-1-bartosz.golaszewski@linaro.org> <20230828192507.117334-4-bartosz.golaszewski@linaro.org> In-Reply-To: From: Bartosz Golaszewski Date: Tue, 17 Oct 2023 10:29:58 +0200 Message-ID: Subject: Re: [PATCH 03/11] firmware: qcom-scm: atomically assign and read the global __scm pointer To: Om Prakash Singh Cc: Andy Gross , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Catalin Marinas , Will Deacon , Arnd Bergmann , Alex Elder , Srini Kandagatla , kernel@quicinc.com, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231017_013010_766945_14B5E5A0 X-CRM114-Status: GOOD ( 25.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 17 Oct 2023 at 10:25, Om Prakash Singh wrote: > > > > On 8/29/2023 12:54 AM, Bartosz Golaszewski wrote: > > Checking for the availability of SCM bridge can happen from any context. > > It's only by chance that we haven't run into concurrency issues but with > > the upcoming SHM Bridge driver that will be initiated at the same > > initcall level, we need to assure the assignment and readback of the > > __scm pointer is atomic. > > > > Signed-off-by: Bartosz Golaszewski > > --- > > drivers/firmware/qcom_scm.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c > > index 980fcfa20b9f..422de70faff8 100644 > > --- a/drivers/firmware/qcom_scm.c > > +++ b/drivers/firmware/qcom_scm.c > > @@ -1331,7 +1331,7 @@ static int qcom_scm_find_dload_address(struct device *dev, u64 *addr) > > */ > > bool qcom_scm_is_available(void) > > { > > - return !!__scm; > > + return !!READ_ONCE(__scm); > > } > > EXPORT_SYMBOL(qcom_scm_is_available); > > > > @@ -1477,8 +1477,8 @@ static int qcom_scm_probe(struct platform_device *pdev) > > if (ret) > > return ret; > > > > - __scm = scm; > > - __scm->dev = &pdev->dev; > > + scm->dev = &pdev->dev; > > + WRITE_ONCE(__scm, scm); > > In my opinion "__scm = scm;" assignment should be done at the end of > probe function success so that qcom_scm_is_available() return true only > when probe is completed. > > Other changes may not be needed. > Om, this is v1. We're at v4 (soon v5). I agree with the comment but it's outside the scope of this series. I may address it later. It has been like this for a long time. Typically this module is built-in and initialized before all other drivers so it has never caused problems. Bart > > init_completion(&__scm->waitq_comp); > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel