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Message-ID: <20160304103649.5be6a46b@gandalf.local.home>
Date: Fri, 4 Mar 2016 10:36:49 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Matt Fleming <matt@...eblueprint.co.uk>,
Daniel Wagner <daniel.wagner@...-carit.de>
Subject: [GIT PULL] tracing: Do not have 'comm' filter override event 'comm'
field
Linus,
A feature was added in 4.3 that allowed users to filter trace points on
a task's "comm" field. But this prevented filtering on a comm field that
is within a trace event (like sched_migrate_task).
When trying to filter on when a program migrated, this change prevented
the filtering of the sched_migrate_task.
To fix this, the event fields are examined first, and then the extra fields
like "comm" and "cpu" are examined. Also, instead of testing to assign
the comm filter function based on the field's name, the generic comm field
is given a new filter type (FILTER_COMM). When this field is used to filter
the type is checked. The same is done for the cpu filter field.
Two new special filter types are added: "COMM" and "CPU". This allows users
to still filter the tasks comm for events that have "comm" as one of their
fields, in cases that users would like to filter sched_migrate_task on the
comm of the task that called the event, and not the comm of the task that
is being migrated.
Please pull the latest trace-fixes-v4.5-rc6 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-fixes-v4.5-rc6
Tag SHA1: d95a2100d788934803c86722bf35b105b6357cd1
Head SHA1: e57cbaf0eb006eaa207395f3bfd7ce52c1b5539c
Steven Rostedt (Red Hat) (1):
tracing: Do not have 'comm' filter override event 'comm' field
----
include/linux/trace_events.h | 2 ++
kernel/trace/trace_events.c | 14 ++++++++------
kernel/trace/trace_events_filter.c | 13 +++++++------
3 files changed, 17 insertions(+), 12 deletions(-)
---------------------------
commit e57cbaf0eb006eaa207395f3bfd7ce52c1b5539c
Author: Steven Rostedt (Red Hat) <rostedt@...dmis.org>
Date: Thu Mar 3 17:18:20 2016 -0500
tracing: Do not have 'comm' filter override event 'comm' field
Commit 9f61668073a8d "tracing: Allow triggers to filter for CPU ids and
process names" added a 'comm' filter that will filter events based on the
current tasks struct 'comm'. But this now hides the ability to filter events
that have a 'comm' field too. For example, sched_migrate_task trace event.
That has a 'comm' field of the task to be migrated.
echo 'comm == "bash"' > events/sched_migrate_task/filter
will now filter all sched_migrate_task events for tasks named "bash" that
migrates other tasks (in interrupt context), instead of seeing when "bash"
itself gets migrated.
This fix requires a couple of changes.
1) Change the look up order for filter predicates to look at the events
fields before looking at the generic filters.
2) Instead of basing the filter function off of the "comm" name, have the
generic "comm" filter have its own filter_type (FILTER_COMM). Test
against the type instead of the name to assign the filter function.
3) Add a new "COMM" filter that works just like "comm" but will filter based
on the current task, even if the trace event contains a "comm" field.
Do the same for "cpu" field, adding a FILTER_CPU and a filter "CPU".
Cc: stable@...r.kernel.org # v4.3+
Fixes: 9f61668073a8d "tracing: Allow triggers to filter for CPU ids and process names"
Reported-by: Matt Fleming <matt@...eblueprint.co.uk>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 429fdfc3baf5..925730bc9fc1 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -568,6 +568,8 @@ enum {
FILTER_DYN_STRING,
FILTER_PTR_STRING,
FILTER_TRACE_FN,
+ FILTER_COMM,
+ FILTER_CPU,
};
extern int trace_event_raw_init(struct trace_event_call *call);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ab09829d3b97..05ddc0820771 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -97,16 +97,16 @@ trace_find_event_field(struct trace_event_call *call, char *name)
struct ftrace_event_field *field;
struct list_head *head;
- field = __find_event_field(&ftrace_generic_fields, name);
+ head = trace_get_fields(call);
+ field = __find_event_field(head, name);
if (field)
return field;
- field = __find_event_field(&ftrace_common_fields, name);
+ field = __find_event_field(&ftrace_generic_fields, name);
if (field)
return field;
- head = trace_get_fields(call);
- return __find_event_field(head, name);
+ return __find_event_field(&ftrace_common_fields, name);
}
static int __trace_define_field(struct list_head *head, const char *type,
@@ -171,8 +171,10 @@ static int trace_define_generic_fields(void)
{
int ret;
- __generic_field(int, cpu, FILTER_OTHER);
- __generic_field(char *, comm, FILTER_PTR_STRING);
+ __generic_field(int, CPU, FILTER_CPU);
+ __generic_field(int, cpu, FILTER_CPU);
+ __generic_field(char *, COMM, FILTER_COMM);
+ __generic_field(char *, comm, FILTER_COMM);
return ret;
}
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index f93a219b18da..6816302542b2 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1043,13 +1043,14 @@ static int init_pred(struct filter_parse_state *ps,
return -EINVAL;
}
- if (is_string_field(field)) {
+ if (field->filter_type == FILTER_COMM) {
+ filter_build_regex(pred);
+ fn = filter_pred_comm;
+ pred->regex.field_len = TASK_COMM_LEN;
+ } else if (is_string_field(field)) {
filter_build_regex(pred);
- if (!strcmp(field->name, "comm")) {
- fn = filter_pred_comm;
- pred->regex.field_len = TASK_COMM_LEN;
- } else if (field->filter_type == FILTER_STATIC_STRING) {
+ if (field->filter_type == FILTER_STATIC_STRING) {
fn = filter_pred_string;
pred->regex.field_len = field->size;
} else if (field->filter_type == FILTER_DYN_STRING)
@@ -1072,7 +1073,7 @@ static int init_pred(struct filter_parse_state *ps,
}
pred->val = val;
- if (!strcmp(field->name, "cpu"))
+ if (field->filter_type == FILTER_CPU)
fn = filter_pred_cpu;
else
fn = select_comparison_fn(pred->op, field->size,
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