From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936476AbdIYVio (ORCPT ); Mon, 25 Sep 2017 17:38:44 -0400 Received: from mga04.intel.com ([192.55.52.120]:47576 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934892AbdIYVim (ORCPT ); Mon, 25 Sep 2017 17:38:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,437,1500966000"; d="scan'208";a="153223501" Date: Mon, 25 Sep 2017 14:38:41 -0700 From: "Luck, Tony" To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Boris Petkov , Fenghua Yu , Reinette Chatre , Steven Rostedt , Vikas Shivappa Subject: Re: [PATCH 2/5] x86/intel_rdt: Add diagnostics when writing the schemata file Message-ID: <20170925213840.t7mchepxvelbagao@intel.com> References: <29bafcfe886a22c6b9b68868f021193e55e5bcf2.1505771973.git.tony.luck@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 25, 2017 at 04:04:07PM +0200, Thomas Gleixner wrote: > On Mon, 18 Sep 2017, Luck, Tony wrote: > > @@ -208,14 +241,19 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, > > char *tok, *resname; > > int closid, ret = 0; > > > > + seq_buf_clear(&last_cmd_status); > > + > > /* Valid input requires a trailing newline */ > > - if (nbytes == 0 || buf[nbytes - 1] != '\n') > > + if (nbytes == 0 || buf[nbytes - 1] != '\n') { > > + seq_buf_puts(&last_cmd_status, "no trailing newline\n"); > > return -EINVAL; > > + } > > buf[nbytes - 1] = '\0'; > > In all other instances you access last_cmd_status within the > rdtgroup_kn_lock_live() protected section, which also serializes the show() > function via rdtgroup_mutex. Here you do it outside for obvious reasons, > but that opens a can of evil worms ... Indeed. > Can you please provide and use two helpers - last_cmd_buf_clear() and > last_cmd_buf_puts() - which both have a > lockdep_assert_held(&rdtgroup_mutex) inside to make sure that we don't end > up with unprotected access accidentally? Sure. In progress. But I also need a last_cmd_printf(), which for some reason is giving me grief. In the header file I put: +static inline void last_cmd_printf(const char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + lockdep_assert_held(&rdtgroup_mutex); + seq_buf_printf(&last_cmd_status, fmt, ap); + va_end(ap); +} and use it like this: + last_cmd_printf("unknown/unsupported resource name '%s'\n", resname); but the argument gets lost/mangled. Instead of the string that should have appeared for the %s, I just get a \b Also with nummeric arguments: + last_cmd_printf("mask %lx has non-consecutive 1-bits\n", val); I get some kernel pointer looking value instead of "5": mask ffffa1ee62757c98 has non-consecutive 1-bits Is there a limit on how many nested va_start()/va_end() can happen? Or is the compiler confused because I made this "inline"? Or just a silly typo that I can't see despite staring at it for a while? -Tony