diff options
| author | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-03-02 06:29:04 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-03-08 21:12:54 +0300 |
| commit | 452f64ee0940a7e7c047f991fccde4efdfbe0d2a (patch) | |
| tree | 1411ac88342c501ef6df9b67d2aff0cc18bb9609 /kernel | |
| parent | aa6d3eef28f348f1fed15e9ebac9752f93b8a9b9 (diff) | |
| download | linux-452f64ee0940a7e7c047f991fccde4efdfbe0d2a.tar.xz | |
tracing/histogram: Fix sorting on old "cpu" value
commit 1d1898f65616c4601208963c3376c1d828cbf2c7 upstream.
When trying to add a histogram against an event with the "cpu" field, it
was impossible due to "cpu" being a keyword to key off of the running CPU.
So to fix this, it was changed to "common_cpu" to match the other generic
fields (like "common_pid"). But since some scripts used "cpu" for keying
off of the CPU (for events that did not have "cpu" as a field, which is
most of them), a backward compatibility trick was added such that if "cpu"
was used as a key, and the event did not have "cpu" as a field name, then
it would fallback and switch over to "common_cpu".
This fix has a couple of subtle bugs. One was that when switching over to
"common_cpu", it did not change the field name, it just set a flag. But
the code still found a "cpu" field. The "cpu" field is used for filtering
and is returned when the event does not have a "cpu" field.
This was found by:
# cd /sys/kernel/tracing
# echo hist:key=cpu,pid:sort=cpu > events/sched/sched_wakeup/trigger
# cat events/sched/sched_wakeup/hist
Which showed the histogram unsorted:
{ cpu: 19, pid: 1175 } hitcount: 1
{ cpu: 6, pid: 239 } hitcount: 2
{ cpu: 23, pid: 1186 } hitcount: 14
{ cpu: 12, pid: 249 } hitcount: 2
{ cpu: 3, pid: 994 } hitcount: 5
Instead of hard coding the "cpu" checks, take advantage of the fact that
trace_event_field_field() returns a special field for "cpu" and "CPU" if
the event does not have "cpu" as a field. This special field has the
"filter_type" of "FILTER_CPU". Check that to test if the returned field is
of the CPU type instead of doing the string compare.
Also, fix the sorting bug by testing for the hist_field flag of
HIST_FIELD_FL_CPU when setting up the sort routine. Otherwise it will use
the special CPU field to know what compare routine to use, and since that
special field does not have a size, it returns tracing_map_cmp_none.
Cc: stable@vger.kernel.org
Fixes: 1e3bac71c505 ("tracing/histogram: Rename "cpu" to "common_cpu"")
Reported-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace_events_hist.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 918f969dffcf..ea168d42c8a2 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -2049,9 +2049,9 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file, /* * For backward compatibility, if field_name * was "cpu", then we treat this the same as - * common_cpu. + * common_cpu. This also works for "CPU". */ - if (strcmp(field_name, "cpu") == 0) { + if (field && field->filter_type == FILTER_CPU) { *flags |= HIST_FIELD_FL_CPU; } else { hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, @@ -4478,7 +4478,7 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data) if (hist_field->flags & HIST_FIELD_FL_STACKTRACE) cmp_fn = tracing_map_cmp_none; - else if (!field) + else if (!field || hist_field->flags & HIST_FIELD_FL_CPU) cmp_fn = tracing_map_cmp_num(hist_field->size, hist_field->is_signed); else if (is_string_field(field)) |