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tracing: Add hist trigger snapshot() action
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Add support for hist:handlerXXX($var).snapshot(), which will take a
snapshot of the current trace buffer whenever handlerXXX is hit.

As a first user, this also adds snapshot() action support for the
onmax() handler i.e. hist:onmax($var).snapshot().

Also, the hist trigger key printing is moved into a separate function
so the snapshot() action can print a histogram key outside the
histogram display - add and use hist_trigger_print_key() for that
purpose.

Link: http://lkml.kernel.org/r/2f1a952c0dcd8aca8702ce81269581a692396d45.1550100284.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Tom Zanussi authored and Steven Rostedt (VMware) committed Feb 20, 2019
1 parent a35873a commit a3785b7
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Showing 2 changed files with 259 additions and 10 deletions.
3 changes: 3 additions & 0 deletions kernel/trace/trace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4919,6 +4919,9 @@ static const char readme_msg[] =
"\t The available actions are:\n\n"
"\t <synthetic_event>(param list) - generate synthetic event\n"
"\t save(field,...) - save current event fields\n"
#ifdef CONFIG_TRACER_SNAPSHOT
"\t snapshot() - snapshot the trace buffer\n"
#endif
#endif
;

Expand Down
266 changes: 256 additions & 10 deletions kernel/trace/trace_events_hist.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -396,6 +396,7 @@ enum handler_id {
enum action_id {
ACTION_SAVE = 1,
ACTION_TRACE,
ACTION_SNAPSHOT,
};

struct action_data {
Expand Down Expand Up @@ -454,6 +455,83 @@ struct action_data {
};
};

struct track_data {
u64 track_val;
bool updated;

unsigned int key_len;
void *key;
struct tracing_map_elt elt;

struct action_data *action_data;
struct hist_trigger_data *hist_data;
};

struct hist_elt_data {
char *comm;
u64 *var_ref_vals;
char *field_var_str[SYNTH_FIELDS_MAX];
};

struct snapshot_context {
struct tracing_map_elt *elt;
void *key;
};

static void track_data_free(struct track_data *track_data)
{
struct hist_elt_data *elt_data;

if (!track_data)
return;

kfree(track_data->key);

elt_data = track_data->elt.private_data;
if (elt_data) {
kfree(elt_data->comm);
kfree(elt_data);
}

kfree(track_data);
}

static struct track_data *track_data_alloc(unsigned int key_len,
struct action_data *action_data,
struct hist_trigger_data *hist_data)
{
struct track_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
struct hist_elt_data *elt_data;

if (!data)
return ERR_PTR(-ENOMEM);

data->key = kzalloc(key_len, GFP_KERNEL);
if (!data->key) {
track_data_free(data);
return ERR_PTR(-ENOMEM);
}

data->key_len = key_len;
data->action_data = action_data;
data->hist_data = hist_data;

elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
if (!elt_data) {
track_data_free(data);
return ERR_PTR(-ENOMEM);
}
data->elt.private_data = elt_data;

elt_data->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
if (!elt_data->comm) {
track_data_free(data);
return ERR_PTR(-ENOMEM);
}

return data;
}

static char last_hist_cmd[MAX_FILTER_STR_VAL];
static char hist_err_str[MAX_FILTER_STR_VAL];

Expand Down Expand Up @@ -1726,12 +1804,6 @@ static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
return hist_field;
}

struct hist_elt_data {
char *comm;
u64 *var_ref_vals;
char *field_var_str[SYNTH_FIELDS_MAX];
};

static u64 hist_field_var_ref(struct hist_field *hist_field,
struct tracing_map_elt *elt,
struct ring_buffer_event *rbe,
Expand Down Expand Up @@ -3452,6 +3524,112 @@ static bool check_track_val(struct tracing_map_elt *elt,
return data->track_data.check_val(track_val, var_val);
}

#ifdef CONFIG_TRACER_SNAPSHOT
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
/* called with tr->max_lock held */
struct track_data *track_data = tr->cond_snapshot->cond_data;
struct hist_elt_data *elt_data, *track_elt_data;
struct snapshot_context *context = cond_data;
u64 track_val;

if (!track_data)
return false;

track_val = get_track_val(track_data->hist_data, context->elt,
track_data->action_data);

track_data->track_val = track_val;
memcpy(track_data->key, context->key, track_data->key_len);

elt_data = context->elt->private_data;
track_elt_data = track_data->elt.private_data;
if (elt_data->comm)
memcpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);

track_data->updated = true;

return true;
}

static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt, void *rec,
struct ring_buffer_event *rbe, void *key,
struct action_data *data,
u64 *var_ref_vals)
{
struct trace_event_file *file = hist_data->event_file;
struct snapshot_context context;

context.elt = elt;
context.key = key;

tracing_snapshot_cond(file->tr, &context);
}

static void hist_trigger_print_key(struct seq_file *m,
struct hist_trigger_data *hist_data,
void *key,
struct tracing_map_elt *elt);

static struct action_data *snapshot_action(struct hist_trigger_data *hist_data)
{
unsigned int i;

if (!hist_data->n_actions)
return NULL;

for (i = 0; i < hist_data->n_actions; i++) {
struct action_data *data = hist_data->actions[i];

if (data->action == ACTION_SNAPSHOT)
return data;
}

return NULL;
}

static void track_data_snapshot_print(struct seq_file *m,
struct hist_trigger_data *hist_data)
{
struct trace_event_file *file = hist_data->event_file;
struct track_data *track_data;
struct action_data *action;

track_data = tracing_cond_snapshot_data(file->tr);
if (!track_data)
return;

if (!track_data->updated)
return;

action = snapshot_action(hist_data);
if (!action)
return;

seq_puts(m, "\nSnapshot taken (see tracing/snapshot). Details:\n");
seq_printf(m, "\ttriggering value { %s(%s) }: %10llu",
action->handler == HANDLER_ONMAX ? "onmax" : "onchange",
action->track_data.var_str, track_data->track_val);

seq_puts(m, "\ttriggered by event with key: ");
hist_trigger_print_key(m, hist_data, track_data->key, &track_data->elt);
seq_putc(m, '\n');
}
#else
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
return false;
}
static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt, void *rec,
struct ring_buffer_event *rbe, void *key,
struct action_data *data,
u64 *var_ref_vals) {}
static void track_data_snapshot_print(struct seq_file *m,
struct hist_trigger_data *hist_data) {}
#endif /* CONFIG_TRACER_SNAPSHOT */

static void track_data_print(struct seq_file *m,
struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt,
Expand All @@ -3463,6 +3641,9 @@ static void track_data_print(struct seq_file *m,
if (data->handler == HANDLER_ONMAX)
seq_printf(m, "\n\tmax: %10llu", track_val);

if (data->action == ACTION_SNAPSHOT)
return;

for (i = 0; i < hist_data->n_save_vars; i++) {
struct hist_field *save_val = hist_data->save_vars[i]->val;
struct hist_field *save_var = hist_data->save_vars[i]->var;
Expand Down Expand Up @@ -3513,9 +3694,21 @@ static void action_data_destroy(struct action_data *data)
static void track_data_destroy(struct hist_trigger_data *hist_data,
struct action_data *data)
{
struct trace_event_file *file = hist_data->event_file;

destroy_hist_field(data->track_data.track_var, 0);
destroy_hist_field(data->track_data.var_ref, 0);

if (data->action == ACTION_SNAPSHOT) {
struct track_data *track_data;

track_data = tracing_cond_snapshot_data(file->tr);
if (track_data && track_data->hist_data == hist_data) {
tracing_snapshot_cond_disable(file->tr);
track_data_free(track_data);
}
}

kfree(data->track_data.var_str);

action_data_destroy(data);
Expand Down Expand Up @@ -3646,6 +3839,26 @@ static int action_parse(char *str, struct action_data *data,
data->track_data.save_data = save_track_data_vars;
data->fn = ontrack_action;
data->action = ACTION_SAVE;
} else if (str_has_prefix(action_name, "snapshot")) {
char *params = strsep(&str, ")");

if (!str) {
hist_err("action parsing: No closing paren found: %s", params);
ret = -EINVAL;
goto out;
}

if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
else {
hist_err("action parsing: Handler doesn't support action: ", action_name);
ret = -EINVAL;
goto out;
}

data->track_data.save_data = save_track_data_snapshot;
data->fn = ontrack_action;
data->action = ACTION_SNAPSHOT;
} else {
char *params = strsep(&str, ")");

Expand Down Expand Up @@ -3942,6 +4155,8 @@ static int trace_action_create(struct hist_trigger_data *hist_data,
static int action_create(struct hist_trigger_data *hist_data,
struct action_data *data)
{
struct trace_event_file *file = hist_data->event_file;
struct track_data *track_data;
struct field_var *field_var;
unsigned int i;
char *param;
Expand All @@ -3950,6 +4165,21 @@ static int action_create(struct hist_trigger_data *hist_data,
if (data->action == ACTION_TRACE)
return trace_action_create(hist_data, data);

if (data->action == ACTION_SNAPSHOT) {
track_data = track_data_alloc(hist_data->key_size, data, hist_data);
if (IS_ERR(track_data)) {
ret = PTR_ERR(track_data);
goto out;
}

ret = tracing_snapshot_cond_enable(file->tr, track_data,
cond_snapshot_update);
if (ret)
track_data_free(track_data);

goto out;
}

if (data->action == ACTION_SAVE) {
if (hist_data->n_save_vars) {
ret = -EEXIST;
Expand Down Expand Up @@ -4552,6 +4782,9 @@ static void print_actions(struct seq_file *m,
for (i = 0; i < hist_data->n_actions; i++) {
struct action_data *data = hist_data->actions[i];

if (data->action == ACTION_SNAPSHOT)
continue;

if (data->handler == HANDLER_ONMAX)
track_data_print(m, hist_data, elt, data);
}
Expand Down Expand Up @@ -4946,10 +5179,10 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
}
}

static void
hist_trigger_entry_print(struct seq_file *m,
struct hist_trigger_data *hist_data, void *key,
struct tracing_map_elt *elt)
static void hist_trigger_print_key(struct seq_file *m,
struct hist_trigger_data *hist_data,
void *key,
struct tracing_map_elt *elt)
{
struct hist_field *key_field;
char str[KSYM_SYMBOL_LEN];
Expand Down Expand Up @@ -5025,6 +5258,17 @@ hist_trigger_entry_print(struct seq_file *m,
seq_puts(m, " ");

seq_puts(m, "}");
}

static void hist_trigger_entry_print(struct seq_file *m,
struct hist_trigger_data *hist_data,
void *key,
struct tracing_map_elt *elt)
{
const char *field_name;
unsigned int i;

hist_trigger_print_key(m, hist_data, key, elt);

seq_printf(m, " hitcount: %10llu",
tracing_map_read_sum(elt, HITCOUNT_IDX));
Expand Down Expand Up @@ -5091,6 +5335,8 @@ static void hist_trigger_show(struct seq_file *m,
if (n_entries < 0)
n_entries = 0;

track_data_snapshot_print(m, hist_data);

seq_printf(m, "\nTotals:\n Hits: %llu\n Entries: %u\n Dropped: %llu\n",
(u64)atomic64_read(&hist_data->map->hits),
n_entries, (u64)atomic64_read(&hist_data->map->drops));
Expand Down

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