Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753622AbXJIBQS (ORCPT ); Mon, 8 Oct 2007 21:16:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751589AbXJIBQK (ORCPT ); Mon, 8 Oct 2007 21:16:10 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:46762 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751469AbXJIBQI (ORCPT ); Mon, 8 Oct 2007 21:16:08 -0400 Date: Mon, 8 Oct 2007 18:15:51 -0700 From: Tim Pepper To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: [PATCH] lockdep: Avoid /proc/lockdep & lock_stat infinite output Message-ID: <20071009011551.GA3592@tpepper-t42p.dolavim.us> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.14 (2007-02-12) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2840 Lines: 91 When a read() requests an amount of data smaller than the amount of data that the seq_file's foo_show() outputs, the output starts looping and outputs the "stuck" element's data infinitely. There may be multiple sequential calls to foo_start(), foo_next()/foo_show(), and foo_stop() for a single open with sequential read of the file. The _start() does not have to start with the 0th element and _show() might be called multiple times in a row for the same element for a given open/read of the seq_file. Signed-off-by: Tim Pepper Cc: Peter Zijlstra Cc: Ingo Molnar --- Assuming people are fine with this, it should probably find its way to stable. If you haven't seen the infinite output: it's easy to trigger with a simple 'cat /proc/lockdep' generally for me, a cat /proc/lock_stat piped to a file or for either of them a dd with the default bs=512 (or smaller) should do the job also. With this change to the lock_stat handler the data->iter member no longer attempts to hold state across calls, so it could be taken out of the lock_stat_seq struct and replace by a local variable in each function but that isn't a clear win to me so I just left it. --- linux-2.6.23-rc9.orig/kernel/lockdep_proc.c +++ linux-2.6.23-rc9/kernel/lockdep_proc.c @@ -34,19 +34,23 @@ static void *l_next(struct seq_file *m, lock_entry); else class = NULL; - m->private = class; return class; } static void *l_start(struct seq_file *m, loff_t *pos) { - struct lock_class *class = m->private; + struct lock_class *class; + loff_t i = 0; - if (&class->lock_entry == all_lock_classes.next) + if (*pos == 0) seq_printf(m, "all lock classes:\n"); + list_for_each_entry(class, &all_lock_classes, lock_entry) { + if (i++ == *pos) + return class; + } + return NULL; - return class; } static void l_stop(struct seq_file *m, void *v) @@ -101,7 +105,7 @@ static void print_name(struct seq_file * static int l_show(struct seq_file *m, void *v) { unsigned long nr_forward_deps, nr_backward_deps; - struct lock_class *class = m->private; + struct lock_class *class = v; struct lock_list *entry; char c1, c2, c3, c4; @@ -523,12 +527,15 @@ static void *ls_start(struct seq_file *m { struct lock_stat_seq *data = m->private; - if (data->iter == data->stats) - seq_header(m); + data->iter = data->stats; + data->iter += *pos; - if (data->iter == data->iter_end) + if (data->iter >= data->iter_end) data->iter = NULL; + if (data->iter == data->stats) + seq_header(m); + return data->iter; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/