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Message-ID: <55479339.6080707@monom.org>
Date: Mon, 04 May 2015 17:41:45 +0200
From: Daniel Wagner <wagi@...om.org>
To: Daniel Wagner <daniel.wagner@...-carit.de>,
Steven Rostedt <rostedt@...dmis.org>,
Tom Zanussi <tom.zanussi@...ux.intel.com>
CC: Ingo Molnar <mingo@...hat.com>, Carsten Emde <C.Emde@...dl.org>,
linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFD 5/5] tracing: Add trace_irqsoff tracepoints
On 05/04/2015 04:05 PM, Daniel Wagner wrote:
> On 05/01/2015 11:23 AM, Daniel Wagner wrote:
>> On 05/01/2015 02:54 AM, Steven Rostedt wrote:
>>> On Thu, 30 Apr 2015 21:14:52 -0500
>>> Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
>>>
>>>
>>>>> 'hist:key=latency.bucket:val=hitcount:sort=latency if cpu==0'
>>>>>
>>>>> but I haven't got this working. I didn't spend much time figuring out
>>>>> why this doesn't work. Even if the above is working you still
>>>>
>>>> I think it doesn't work because the tracepoint doesn't actually have a
>>>> 'cpu' field to use in the filter...
>>>
>>> Perhaps we should add special fields that don't use the tracepoint
>>> field, but can use generically know fields that are always known when
>>> the tracepoint is triggered. COMM could be one, as well as CPU.
Here my second attempt.
Changes v0:
- Added COMM filter predicate
- Avoid API break in format by introducing a new list for
generic fields
>From 10a58dcc9157ef29514b237aa5d5d8412365a389 Mon Sep 17 00:00:00 2001
From: Daniel Wagner <daniel.wagner@...-carit.de>
Date: Mon, 4 May 2015 15:44:24 +0200
Subject: [PATCH] tracing: Allow triggers to filter for CPUs and COMM
By extending the filter rules by more generic fields
we can write triggers filters like
echo 'stacktrace if cpu == 1' > \
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
or
echo 'stacktrace if comm == sshd' > \
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
We don't want to change the API for the format files. Therefore a new
list (ftrace_generic_fields) is introduced and by this we avoid
getting them listed.
Not for inclusion!
Not-Signed-off-by: Daniel Wagner <daniel.wagner@...-carit.de>
---
kernel/trace/trace_events.c | 25 ++++++++++++++++++
kernel/trace/trace_events_filter.c | 54 ++++++++++++++++++++++++++++++++++++--
2 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c4de47f..805cb75 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -30,6 +30,7 @@
DEFINE_MUTEX(event_mutex);
LIST_HEAD(ftrace_events);
+static LIST_HEAD(ftrace_generic_fields);
static LIST_HEAD(ftrace_common_fields);
#define GFP_TRACE (GFP_KERNEL | __GFP_ZERO)
@@ -94,6 +95,10 @@ trace_find_event_field(struct ftrace_event_call *call, char *name)
struct ftrace_event_field *field;
struct list_head *head;
+ field = __find_event_field(&ftrace_generic_fields, name);
+ if (field)
+ return field;
+
field = __find_event_field(&ftrace_common_fields, name);
if (field)
return field;
@@ -144,6 +149,13 @@ int trace_define_field(struct ftrace_event_call *call, const char *type,
}
EXPORT_SYMBOL_GPL(trace_define_field);
+#define __generic_field(type, item, filter_type) \
+ ret = __trace_define_field(&ftrace_generic_fields, #type, \
+ #item, 0, 0, is_signed_type(type), \
+ filter_type); \
+ if (ret) \
+ return ret;
+
#define __common_field(type, item) \
ret = __trace_define_field(&ftrace_common_fields, #type, \
"common_" #item, \
@@ -153,6 +165,16 @@ EXPORT_SYMBOL_GPL(trace_define_field);
if (ret) \
return ret;
+static int trace_define_generic_fields(void)
+{
+ int ret;
+
+ __generic_field(int, cpu, FILTER_OTHER);
+ __generic_field(char *, comm, FILTER_PTR_STRING);
+
+ return ret;
+}
+
static int trace_define_common_fields(void)
{
int ret;
@@ -2671,6 +2693,9 @@ static __init int event_trace_init(void)
if (!entry)
pr_warn("Could not create tracefs 'available_events' entry\n");
+ if (trace_define_generic_fields())
+ pr_warn("tracing: Failed to allocated generic fields");
+
if (trace_define_common_fields())
pr_warn("tracing: Failed to allocate common fields");
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index ced69da..74feaf4 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -252,6 +252,50 @@ static int filter_pred_strloc(struct filter_pred *pred, void *event)
return match;
}
+/* Filter predicate for CPUs. */
+static int filter_pred_cpu(struct filter_pred *pred, void *event)
+{
+ int cpu, cmp;
+ int match = 0;
+
+ cpu = raw_smp_processor_id();
+ cmp = pred->val;
+
+ switch (pred->op) {
+ case OP_EQ:
+ match = cpu == cmp;
+ break;
+ case OP_LT:
+ match = cpu < cmp;
+ break;
+ case OP_LE:
+ match = cpu <= cmp;
+ break;
+ case OP_GT:
+ match = cpu > cmp;
+ break;
+ case OP_GE:
+ match = cpu >= cmp;
+ break;
+ default:
+ break;
+ }
+
+ return !!match == !pred->not;
+}
+
+/* Filter predicate for COMM. */
+static int filter_pred_comm(struct filter_pred *pred, void *event)
+{
+ int cmp, match;
+
+ cmp = pred->regex.match(current->comm, &pred->regex,
+ pred->regex.field_len);
+ match = cmp ^ pred->not;
+
+ return match;
+}
+
static int filter_pred_none(struct filter_pred *pred, void *event)
{
return 0;
@@ -1002,7 +1046,10 @@ static int init_pred(struct filter_parse_state *ps,
if (is_string_field(field)) {
filter_build_regex(pred);
- if (field->filter_type == FILTER_STATIC_STRING) {
+ if (!strcmp(field->name, "comm")) {
+ fn = filter_pred_comm;
+ pred->regex.field_len = TASK_COMM_LEN;
+ } else 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)
@@ -1025,7 +1072,10 @@ static int init_pred(struct filter_parse_state *ps,
}
pred->val = val;
- fn = select_comparison_fn(pred->op, field->size,
+ if (!strcmp(field->name, "cpu"))
+ fn = filter_pred_cpu;
+ else
+ fn = select_comparison_fn(pred->op, field->size,
field->is_signed);
if (!fn) {
parse_error(ps, FILT_ERR_INVALID_OP, 0);
--
2.1.0
--
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