From mboxrd@z Thu Jan 1 00:00:00 1970 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.subspace.kernel.org (Postfix) with ESMTPS id 074751DDC15 for ; Fri, 11 Jul 2025 07:37:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752219454; cv=none; b=X0M//m9ajkmYqyihg+2EvtcLJFpILEVeL0MIwUfVsE8CD3zPwgW/xUpb7yT1fflTq2Lr2YTeAMVsKA5qtYOEg7VhecgNvwo3aHjVM5LFTMd9T2/FYZT6BPTHvr2GOKL8Q49vAnYb2Pnqp1mKi34LUrZxxjRrqC0hUrcR1ghWu5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752219454; c=relaxed/simple; bh=VQSOBblDnH8Nu/vrW+KEgqDWdWu/ONzBiULEcqToVqk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=k0ZoytYVyvl11hw/3/DyMT7g8eeEt5PYvpm0BHpR7Coku8DcjNoLcpqEKQq+Td1PyTvV/uCRvEt3E/UJ/gHGAqy/P8WUgp5GUujxvX5qoF9KDAr3EEMlg129+PALrYpOlTuhWtsufwhBCGUonRQ7KNms8BHItqW62HUjTOLLul4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=vqdOhGHw; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="vqdOhGHw" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KqPiowxiYTxo0biT0p4CeawYRZdkUE5oW6VYmcMOZII=; b=vqdOhGHwJIOPLv/zuAsRV8sNta 2jT+vWaZsMKSkK8l9c2Wcl2vLOA8ZTawD6sW1HdzkZfeWcmOcnMsve68847DTMZ8zBLDbBbpnGHjE 2FK7bXoDkaYo6I3WghRwmKYKSr4eaTI8kXWD126M1mjcARn3aETMc24/C+AOg05cb1zpHxGVZvVoY yzTjSvBMMFfyXPCQP+GJb1Yntw4a7M6/P/rQuxb36crlG6G8U+bBEuoNFDPWRkNOw6ZFhvae3wAuz UptBTs5nEOUy6Xb7AkPFgIdWGgPKbHaNdb8V3Lr6cbQ0TovDObj1vTAgdnsom5A1g9NJDNRRbWo4I fsEJ4mQw==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1ua8K4-0000000DzwI-1OcS; Fri, 11 Jul 2025 07:37:32 +0000 Date: Fri, 11 Jul 2025 00:37:32 -0700 From: Christoph Hellwig To: Mathieu Desnoyers Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Josh Poimboeuf , Masami Hiramatsu , Peter Zijlstra , Ingo Molnar , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , Linus Torvalds , Andrew Morton Subject: Re: [RFC PATCH 3/5] unwind deferred: Introduce unwind_user_trace_cached Message-ID: References: <20250709212556.32777-1-mathieu.desnoyers@efficios.com> <20250709212556.32777-4-mathieu.desnoyers@efficios.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250709212556.32777-4-mathieu.desnoyers@efficios.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Jul 09, 2025 at 05:25:50PM -0400, Mathieu Desnoyers wrote: > Introduce unwind_user_trace_cached which copies the stack trace if it > was previously stored into the cache since the last reset of the cache. > > The expected use-case is sampling a stack trace from a faultable context > at system call entry (coping it into the cache), and then copying the > stack trace from the cache from non-faultable context to a ring buffer. Why is this and the following patches adding unused code?