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 80843C43458 for ; Tue, 30 Jun 2026 19:53:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To: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=LXRxFbi1rHNU7GbafqaihoCDwM1y7YKAsLY1yaGEPbY=; b=FmhuKDQUrBOPgPIWisP0qqO/ah AUNgTSSjNELQ9uxgyaDzwgvm1tZ/lAqzV3z/88+szKybX3vQ+Ns5K3jUW5n+JYNJfGGtTMcCbrVtd FpK9Ob0sNOqsHJxqXWxW4/zNUH6JSGdYtSRgZQH1Em+47Kv/ia/I24C7tZ8VUorVUOkV9ToH1c7Hj c9J45f8tXW3IdqB1CSiKcOKkQh5ndCy5kPLGpbasySan0aeh7/vdCPgtQubhHmT5IL80t94Pao0iw XbtilCWefVInHIkqOeDCKuR6HWKzkPp207ropWfobqm1R3DbouUj597jgjzMN4OJkrFWtfKiK4ucl nNn3YUgg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1weeWJ-0000000092v-1eKi; Tue, 30 Jun 2026 19:53:23 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1weeWH-0000000092L-2G8k for linux-arm-kernel@lists.infradead.org; Tue, 30 Jun 2026 19:53:21 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 8A637600FC; Tue, 30 Jun 2026 19:53:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E8731F000E9; Tue, 30 Jun 2026 19:53:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782849200; bh=LXRxFbi1rHNU7GbafqaihoCDwM1y7YKAsLY1yaGEPbY=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=j8bysIMbzvXmdKPX76RwD72APahTsxjBcVRALpKR9ix/1ivBdJD16BHUPrYRtqs9z nEvIIBNBaYuhBW9hu4SYrBLt4Y5umONwcWicaQzvku6VTUEa/czI1CR55zLYCfL830 64FDP9ixwyz4y012ZdZoTVr0crdxDSUZG2M48yPtiJduV7gtmApxw62BKyxTKncV44 3+TgcmYFn66Lx6+ee5/kNbdSoG+/aIfZvQEta2d9NM5s1QAFV6hdngGSF5ATcQynMk k8YVT8EPm9cU8b2pL9VI9wgcZ0JQGwGByfUtzryk2BrQNwrcJ5PfssTheyXZDhF0cJ bPewcAZS2tarA== Date: Tue, 30 Jun 2026 15:53:18 -0400 From: Steven Rostedt To: Geert Uytterhoeven Cc: David Carlier , linux-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , "Vineeth Pillai (Google)" , Peter Zijlstra , Linux ARM , Linux-Renesas Subject: Re: [for-next][PATCH 04/15] tracepoint: Add lockdep rcu_is_watching() check to trace_##name##_enabled() Message-ID: <20260630155318.7db20990@gandalf.local.home> In-Reply-To: References: <20260522143508.298439732@kernel.org> <20260522143525.551205135@kernel.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 30 Jun 2026 19:39:02 +0200 Geert Uytterhoeven wrote: > Other Renesas ARM32 platforms I tried (R-Mobile A1, RZ/A1H, RZ/A2M) > are unafffected, perhaps because they are not SMP? > All Renesas ARM64 platforms I tried (R-Car Gen3/4) are also unaffected. > > Reverting the commit fixes the issue. > > Do you have a clue? Yes, it means the code was buggy before the commit. The commit will trigger warnings in places that have issues. Before the commit, the buggy code was never caught. It's like enabling KASAN and finding code that has use-after-free. Disabling KASAN is not the fix. Tracepoints are managed by using RCU. There's places that RCU is turned off, meaning a tracepoint in one of those locations can be triggered when RCU is not active which may have a use-after-free semantic when the tracepoint is enabled. Tracepoints hidden by trace_#tracepoint#_enabled() are not caught when RCU is disabled and the tracepoint is not active. This commit makes these locations trigger even when the tracepoint is not active. One way to find out if this is an existing bug or not, could you enable the preemptirq tracepoints and run the tests again with the commit reverted? echo 1 > /sys/kernel/tracing/events/preemptirq/enable This will enable the events that are hidden without the commit. If it triggers when enabled, it shows the commit found a bug. If you get the same errors, the bug isn't with the commit in question, it's with the tracepoints being called during suspend/resume. We will need to fix that if that's the case. -- Steve