From abf4868b8548cae18d4fe8bbfb4e207443be01be Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 20 Nov 2009 22:19:49 +0100 Subject: [PATCH] perf: Fix PERF_FORMAT_GROUP scale info 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 Cc: Paul Mackerras LKML-Reference: <20091120212508.685559857@chello.nl> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 52 ++++++++++++++++++--------------------------- 1 file changed, 21 insertions(+), 31 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 68fbf4ff6888..9a18ff28ea5b 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1784,30 +1784,15 @@ u64 perf_event_read_value(struct perf_event *event) } 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 perf_event *event, 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,