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A feature was added in 4.3 that allowed users to filter trace points on

Browse source 
a tasks "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.
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Merge tag 'trace-fixes-v4.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fix from Steven Rostedt:
 "A feature was added in 4.3 that allowed users to filter trace points
  on a tasks "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"

* tag 'trace-fixes-v4.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Do not have 'comm' filter override event 'comm' field
This commit is contained in:
Linus Torvalds 2016-03-04 16:57:04 -08:00
commit 78baab7aa8
3 changed files with 19 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
include/linux/trace_events.h
View file

@ -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);

18
kernel/trace/trace_events.c
View file

@ -97,16 +97,16 @@ trace_find_event_field(struct trace_event_call *call, char *name)
struct ftrace_event_field *field;
struct list_head *head;
head = trace_get_fields(call);
field = __find_event_field(head, name);
if (field)
return field;
field = __find_event_field(&ftrace_generic_fields, name);
if (field)
return field;
field = __find_event_field(&ftrace_common_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;
}

13
kernel/trace/trace_events_filter.c
View file

@ -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,