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 E4DF6C433F5 for ; Mon, 7 Mar 2022 10:22:38 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1bFueMPyauIPRyWTfmDwL2MX8lEBb3R9jV0id15E3k0=; b=JKd4o35LLHCdc/ aX2ApnILxZC3pH4hEZvHGE8kBdk7J7OsxurlQVmRdlUq/l/eeC7wmGrYnjZKdpPufvU32W0oMn8ne mPrO04lRyKAyM1zyz3E7EcYwgkTmWTjlc5N/vhmgFn2FWGEZlqBbZ9KyGW1+HuhyN9YdKqkQoSF45 jajWBizST+qpI/cg3PalMG2TEUkvIt9UVzXeLszagYRBOgKRLFjmczSTzVCRjnF91RHWn7c9z1GSW IKBGJSRPllT9XebkQWOH5qnWGbA9rWjko+zOnuDLzwN1nAVCjK5phZLQTeOhJq/p9ALsq83f1ni8I EWlbEnnla3xkRgjTk+jA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRAUY-00H45b-KN; Mon, 07 Mar 2022 10:21:26 +0000 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRAUK-00H3zH-Va for linux-arm-kernel@lists.infradead.org; Mon, 07 Mar 2022 10:21:14 +0000 Received: by mail-wm1-x32a.google.com with SMTP id c192so8841032wma.4 for ; Mon, 07 Mar 2022 02:21:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=v44C7e93zXYvCQxCtpONtTzjzcMRf1jrW3PTOB9sjGY=; b=MbcQbyJuVOitnMfJ2A+JHyoPrX+m84l5VMr7Wi8XocBEHfK7oRLPXXDo9KTWJ8wDwl k1oqQq1flwqrxEGcIhMtqyTSyr6ZqO2SqDdpE5QlkuKpv9bnuv97HX3oDiJHld+BTBi1 m8cV3kxPxNngnk6Gfvwwdor34gB67RIgc6xO0e61vs+KUhAkVcUv756I2FDhnewA/Cuz rGc0LqrQiRVH3coJRP5MJ1Vbo5mO2G4WYnaw+QCUBxDwYrP3eHracV2a2NMTR83Q7v9t c6vCvPC5w4pUVzYgfGWiq1IK7imgDIbDNBZyniDTBqLiVLbMutv7tt5BwWyLJNtvQwc6 LPJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=v44C7e93zXYvCQxCtpONtTzjzcMRf1jrW3PTOB9sjGY=; b=ZUpzBOBybQmmiyylGa/4dmRhbb4gP/vc/AReAJkH8U6gXBdXdSQME9h5s/nhjWPAA1 x2oVY1sWvZFdvOiK2Orzz/O9al+iFeIOt7qItgF5n1FHGeJ/S5wLPR9gLVUu2aBSSxuR dtvaWDGYjja56QTdhVdKXS0/lYtfTLk1rMzSa99HEEzQ3nPFf5fwkoDOpYRAZN/g13zd Wz/ysArR4NJC2z2kXFSiCrRHuMD6IHqxCOdjL2FQuHKOxZXCNU7Qn+vutCnhIWWvQnnL 787l+RtiqFeo/u9Gn12Ynk8PjERMbx68yACbTDpA5wlbPkgfhKG4UydL6ahHI5SqCWdi rlSA== X-Gm-Message-State: AOAM533owTcjXwOLtg/a8CVqhliqpzW0CqnPT/7IY+1D+06wMJoJ5sof Q+odagxFnfg3dMX0V5Xs9K8= X-Google-Smtp-Source: ABdhPJzFaGA2eexzJEnSB4wJR3CtKOVSGoFlvEVkl2CzvXX3TTwmZNbebDie00lG7ItxmcFbSgjpug== X-Received: by 2002:a05:600c:3d0b:b0:382:aa17:8f16 with SMTP id bh11-20020a05600c3d0b00b00382aa178f16mr8395713wmb.82.1646648470856; Mon, 07 Mar 2022 02:21:10 -0800 (PST) Received: from Red ([2a01:cb1d:3d5:a100:264b:feff:fe03:2806]) by smtp.googlemail.com with ESMTPSA id t184-20020a1c46c1000000b003814de297fcsm6807056wma.16.2022.03.07.02.21.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Mar 2022 02:21:10 -0800 (PST) Date: Mon, 7 Mar 2022 11:21:07 +0100 From: Corentin Labbe To: Ard Biesheuvel Cc: Linux ARM , Russell King Subject: Re: [PATCH] ARM: return_address: disable again for CONFIG_ARM_UNWIND=y Message-ID: References: <20220302113201.1864406-1-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220307_022113_085372_B04EB72F X-CRM114-Status: GOOD ( 23.58 ) 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="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Le Sat, Mar 05, 2022 at 10:04:23PM +0000, Ard Biesheuvel a =E9crit : > On Sat, 5 Mar 2022 at 20:20, Corentin Labbe w= rote: > > > > Le Wed, Mar 02, 2022 at 12:32:01PM +0100, Ard Biesheuvel a =E9crit : > > > Commit 41918ec82eb6 ("ARM: ftrace: enable the graph tracer with the E= ABI > > > unwinder") removed the dummy version of return_address() that was > > > provided for the CONFIG_ARM_UNWIND=3Dy case, on the assumption that t= he > > > removal of the kernel_text_address() call from unwind_frame() in the > > > preceding patch made it safe to do so. > > > > > > However, this turns out not to be the case: Corentin reports warnings > > > about suspicious RCU usage and other strange behavior that seems to > > > originate in the stack unwinding that occurs in return_address(). > > > > > > Given that the function graph tracer (which is what these changes were > > > enabling for CONFIG_ARM_UNWIND=3Dy builds) does not appear to care ab= out > > > this distinction, let's revert return_address() to the old state. > > > > > > Cc: Corentin Labbe > > > Fixes: 41918ec82eb6 ("ARM: ftrace: enable the graph tracer with the E= ABI unwinder") > > > Signed-off-by: Ard Biesheuvel > > > > Hello > > > > On next-20220304 even with both > > ARM: unwind: avoid spurious warnings on bogus code addresses > > and > > ARM: return_address: disable again for CONFIG_ARM_UNWIND=3Dy > > > > I got: > > [ 0.134043] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > [ 0.138372] WARNING: suspicious RCU usage > > [ 0.142702] 5.17.0-rc6-next-20220304-dirty #3 Not tainted > ... > > [ 1.015443] show_stack from 0xf0991e6c > > > > On next-20220303 I got nothing. > = > This makes me suspect that this is unrelated, given that no changes > were applied to Russell's tree in the mean time, as far as I can tell. Hello I bisected to dc6e0818bc9a0336d9accf3ea35d146d72aa7a18 ("sched/cpuacct: Opt= imize away RCU read lock") but reverting lead to some remaining RCU (but far less than before). I continue to debug it. Regards _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel