From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756272AbZKTVbj (ORCPT ); Fri, 20 Nov 2009 16:31:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755997AbZKTVbf (ORCPT ); Fri, 20 Nov 2009 16:31:35 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34637 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755686AbZKTV22 (ORCPT ); Fri, 20 Nov 2009 16:28:28 -0500 Message-Id: <20091120212508.685559857@chello.nl> References: <20091120211942.676891948@chello.nl> User-Agent: quilt/0.46-1 Date: Fri, 20 Nov 2009 22:19:49 +0100 From: Peter Zijlstra To: Paul Mackerras , Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org Subject: [PATCH 07/15] perf: Fix PERF_FORMAT_GROUP scale info Content-Disposition: inline; filename=perf-time-0.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As Corey reported, the total_enabled and total_running times could occasionally be 0, even though there were events counted. It turns out this is because we record the times before reading the counter while the latter updates the times. This patch corrects that. While looking at this code I found that there is a lot of locking iffyness around, the following patches correct most of that. Reported-by: Corey Ashford Signed-off-by: Peter Zijlstra --- kernel/perf_event.c | 52 +++++++++++++++++++++------------------------------- 1 file changed, 21 insertions(+), 31 deletions(-) Index: linux-2.6/kernel/perf_event.c =================================================================== --- linux-2.6.orig/kernel/perf_event.c +++ linux-2.6/kernel/perf_event.c @@ -1784,30 +1784,15 @@ u64 perf_event_read_value(struct perf_ev } EXPORT_SYMBOL_GPL(perf_event_read_value); -static int perf_event_read_entry(struct perf_event *event, - u64 read_format, char __user *buf) -{ - int n = 0, count = 0; - u64 values[2]; - - values[n++] = perf_event_read_value(event); - if (read_format & PERF_FORMAT_ID) - values[n++] = primary_event_id(event); - - count = n * sizeof(u64); - - if (copy_to_user(buf, values, count)) - return -EFAULT; - - return count; -} - static int perf_event_read_group(struct perf_event *event, u64 read_format, char __user *buf) { struct perf_event *leader = event->group_leader, *sub; - int n = 0, size = 0, err = -EFAULT; - u64 values[3]; + int n = 0, size = 0, ret = 0; + u64 values[5]; + u64 count; + + count = perf_event_read_value(leader); values[n++] = 1 + leader->nr_siblings; if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) { @@ -1818,28 +1803,33 @@ static int perf_event_read_group(struct values[n++] = leader->total_time_running + atomic64_read(&leader->child_total_time_running); } + values[n++] = count; + if (read_format & PERF_FORMAT_ID) + values[n++] = primary_event_id(leader); size = n * sizeof(u64); if (copy_to_user(buf, values, size)) return -EFAULT; - err = perf_event_read_entry(leader, read_format, buf + size); - if (err < 0) - return err; - - size += err; + ret += size; list_for_each_entry(sub, &leader->sibling_list, group_entry) { - err = perf_event_read_entry(sub, read_format, - buf + size); - if (err < 0) - return err; + n = 0; - size += err; + values[n++] = perf_event_read_value(sub); + if (read_format & PERF_FORMAT_ID) + values[n++] = primary_event_id(sub); + + size = n * sizeof(u64); + + if (copy_to_user(buf + size, values, size)) + return -EFAULT; + + ret += size; } - return size; + return ret; } static int perf_event_read_one(struct perf_event *event, --