From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756950Ab3GVOVz (ORCPT ); Mon, 22 Jul 2013 10:21:55 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:19179 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756259Ab3GVOV3 (ORCPT ); Mon, 22 Jul 2013 10:21:29 -0400 X-Authority-Analysis: v=2.0 cv=aqMw+FlV c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=vb2B4RKiyq0A:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=MQtORcZ-KhkA:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=Vp3Nri4IhVGfMBwv4-4A:9 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130722142126.049313184@goodmis.org> User-Agent: quilt/0.60-1 Date: Mon, 22 Jul 2013 10:19:58 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , Masami Hiramatsu , Oleg Nesterov Subject: [PATCH 11/14] tracing: Simplify the iteration logic in f_start/f_next References: <20130722141947.972915744@goodmis.org> Content-Disposition: inline; filename=0011-tracing-Simplify-the-iteration-logic-in-f_start-f_ne.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov f_next() looks overcomplicated, and it is not strictly correct even if this doesn't matter. Say, FORMAT_FIELD_SEPERATOR should not return NULL (means EOF) if trace_get_fields() returns an empty list, we should simply advance to FORMAT_PRINTFMT as we do when we find the end of list. 1. Change f_next() to return "struct list_head *" rather than "ftrace_event_field *", and change f_show() to do list_entry(). This simplifies the code a bit, only f_show() needs to know about ftrace_event_field, and f_next() can play with ->prev directly 2. Change f_next() to not play with ->prev / return inside the switch() statement. It can simply set node = head/common_head, the prev-or-advance-to-the-next-magic below does all work. While at it. f_start() looks overcomplicated too. I don't think *pos == 0 makes sense as a separate case, just change this code to do "while" instead of "do/while". The patch also moves f_start() down, close to f_stop(). This is purely cosmetic, just to make the locking added by the next patch more clear/visible. Link: http://lkml.kernel.org/r/20130718184710.GA4783@redhat.com Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 60 ++++++++++++++++--------------------------- 1 file changed, 22 insertions(+), 38 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 7a75cb2..76defd9 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -826,59 +826,33 @@ enum { static void *f_next(struct seq_file *m, void *v, loff_t *pos) { struct ftrace_event_call *call = m->private; - struct ftrace_event_field *field; struct list_head *common_head = &ftrace_common_fields; struct list_head *head = trace_get_fields(call); + struct list_head *node = v; (*pos)++; switch ((unsigned long)v) { case FORMAT_HEADER: - if (unlikely(list_empty(common_head))) - return NULL; - - field = list_entry(common_head->prev, - struct ftrace_event_field, link); - return field; + node = common_head; + break; case FORMAT_FIELD_SEPERATOR: - if (unlikely(list_empty(head))) - return NULL; - - field = list_entry(head->prev, struct ftrace_event_field, link); - return field; + node = head; + break; case FORMAT_PRINTFMT: /* all done */ return NULL; } - field = v; - if (field->link.prev == common_head) + node = node->prev; + if (node == common_head) return (void *)FORMAT_FIELD_SEPERATOR; - else if (field->link.prev == head) + else if (node == head) return (void *)FORMAT_PRINTFMT; - - field = list_entry(field->link.prev, struct ftrace_event_field, link); - - return field; -} - -static void *f_start(struct seq_file *m, loff_t *pos) -{ - loff_t l = 0; - void *p; - - /* Start by showing the header */ - if (!*pos) - return (void *)FORMAT_HEADER; - - p = (void *)FORMAT_HEADER; - do { - p = f_next(m, p, &l); - } while (p && l < *pos); - - return p; + else + return node; } static int f_show(struct seq_file *m, void *v) @@ -904,8 +878,7 @@ static int f_show(struct seq_file *m, void *v) return 0; } - field = v; - + field = list_entry(v, struct ftrace_event_field, link); /* * Smartly shows the array type(except dynamic array). * Normal: @@ -932,6 +905,17 @@ static int f_show(struct seq_file *m, void *v) return 0; } +static void *f_start(struct seq_file *m, loff_t *pos) +{ + void *p = (void *)FORMAT_HEADER; + loff_t l = 0; + + while (l < *pos && p) + p = f_next(m, p, &l); + + return p; +} + static void f_stop(struct seq_file *m, void *p) { } -- 1.7.10.4