From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-202.mailbox.org (mout-p-202.mailbox.org [80.241.56.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61BA126FD93; Mon, 3 Aug 2026 16:00:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785772854; cv=none; b=h7K4cUx+D4z80ULP3nN+V3V+DQuLAAASvzbD6yJm5RugzqXulbfi6ZYeAdoIyS6ypKTEX18Da000bJFK2dmor2WKw5yb+Mg16bi6hdi8bZeXGjxr2bro2fb5N5YaeTlREH/J2DMbTZPdoH7v5fS7t2iCJQP7cNhf8aO8V01gyNA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785772854; c=relaxed/simple; bh=5royt46sB2EApVX7lNdh4bb6KePS6qMXeTl3J2Aw6/A=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:Subject:From:To: References:In-Reply-To; b=cnZDr+jc8NZN/QOGXlhHIIfpC8sMZe7MyNKwY0z1q79z//6oQ00AEYtouNEo7JzVU8ZNy25EjvCwu0AkRjZEDf4NPQPC2mOmqAfu9tr6Lz17YlgHhIqqJe27rnfp5icH26D7BsOvokVAOJ8dkBHbwpU6z5aqnLp/lG2dNDGzKJw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mavick.dev; spf=pass smtp.mailfrom=mavick.dev; dkim=pass (2048-bit key) header.d=mavick.dev header.i=@mavick.dev header.b=CSEMl0Fv; arc=none smtp.client-ip=80.241.56.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mavick.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mavick.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mavick.dev header.i=@mavick.dev header.b="CSEMl0Fv" Received: from smtp1.mailbox.org (smtp1.mailbox.org [10.196.197.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-202.mailbox.org (Postfix) with ESMTPS id 4hDLxQ09bwzMlDb; Mon, 03 Aug 2026 18:00:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mavick.dev; s=MBO0001; t=1785772842; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5royt46sB2EApVX7lNdh4bb6KePS6qMXeTl3J2Aw6/A=; b=CSEMl0FvXjgg5rH2tEQ4H0KlBTTB+pvEiSLP//gNLi4BAHeLvCxiBaWWj9PcwTOy9Pnq8g H32SNxwD81JajS7NQ1CB6g3uD+l4tX6Ia0Z1tu6/ynmdVkBBSsYBfmVSVUWKD3+FTfq92w 19oEutkvJ4fYYyR8OWlwK4yRJR3YBru5+U7OnaD97G8yHhQT5yF1xIwAgBp1ISr2gf/QFZ tw3q+/rZ4EjbWb/oFTJjoTvcwUgU0S/AyMo0Y5Rwuc0G34662Z2H+LxzNYIkmOEVEPJeV7 Q9nog+1Vp7tUCOqMZY2wmhDg/9v2P4rhjVe1BTcGyIiq4s/2Mepp4d1uUJoGfg== Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 04 Aug 2026 00:00:02 +0800 Message-Id: Cc: "Will Deacon" , "Boqun Feng" , "Mark Rutland" , "Gary Guo" , "Steven Rostedt" , "Masami Hiramatsu" , "Mathieu Desnoyers" , "Andrew Morton" , "Dennis Zhou" , "Tejun Heo" , "Christoph Lameter" , , , Subject: Re: [PATCH v4 0/5] tracing: add ref_trace_final_put tracing From: "Eugene Mavick" To: "Peter Zijlstra" , "Eugene Mavick" References: <20260801-refcount-final-put-trace-v4-0-2e58678f0ffd@mavick.dev> <20260803083750.GA49951@noisy.programming.kicks-ass.net> In-Reply-To: <20260803083750.GA49951@noisy.programming.kicks-ass.net> On Mon Aug 3, 2026 at 4:37 PM +08, Peter Zijlstra wrote: > I'm not sure this Changelog is convincing me. To me this just looks like > more weight / bloat without benefit. The overhead is negligible; like other TRACE_EVENTS this is an if statement when disabled. Knowledge of when an object is considered end-of-usable-life by the refcount implementation is one of the first steps in UAF debugging. Alternatives to obtain this information (GDB, watchpoints, manual instrumentation) require live analysis. When debugging from static information of remote origin, like syzbot, this may not be practical. Live analysis requires bug reproduction and manual effort. Bug reproduction, especially in rare timing-sensitive UAFs that thus require many iterations, may require significant time/hardware resources. This tracepoint eliminates significant effort/time cost, and removes a hardware barrier for a common debugging scenario at a negligible performance cost.