Messages in this thread Patch in this message | | | Date | Fri, 20 Nov 2009 22:19:49 +0100 | From | Peter Zijlstra <> | Subject | [PATCH 07/15] perf: Fix PERF_FORMAT_GROUP scale info |
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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 <cjashfor@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- 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, --
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