From ed2cf90735daf40ab8d938b4b6d3ca43c0f84466 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 22 Jul 2021 10:27:07 -0400 Subject: [PATCH] tracing: Allow execnames to be passed as args for synthetic events Allow common_pid.execname to be saved in a variable in one histogram to be passed to another histogram that can pass it as a parameter to a synthetic event. ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs:arg2=common_pid.execname' \ > events/sched/sched_waking/trigger ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > synthetic_events ># echo 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs-$__arg__1,exec=$arg2'\ ':onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,$exec)' \ > events/sched/sched_switch/trigger The above is a wake up latency synthetic event setup that passes the execname of the common_pid that woke the task to the scheduling of that task, which triggers a synthetic event that passes the original execname as a parameter to display it. ># echo 1 > events/synthetic/enable ># cat trace -0 [006] d..4 186.863801: wakeup_lat: pid=1306 delta=65 wake_comm=kworker/u16:3 -0 [000] d..4 186.863858: wakeup_lat: pid=163 delta=27 wake_comm= -0 [001] d..4 186.863903: wakeup_lat: pid=1307 delta=36 wake_comm=kworker/u16:4 -0 [000] d..4 186.863927: wakeup_lat: pid=163 delta=5 wake_comm= -0 [006] d..4 186.863957: wakeup_lat: pid=1306 delta=24 wake_comm=kworker/u16:3 sshd-1306 [006] d..4 186.864051: wakeup_lat: pid=61 delta=62 wake_comm= -0 [000] d..4 186.965030: wakeup_lat: pid=609 delta=18 wake_comm= -0 [006] d..4 186.987582: wakeup_lat: pid=1306 delta=65 wake_comm=kworker/u16:3 -0 [000] d..4 186.987639: wakeup_lat: pid=163 delta=27 wake_comm= Link: https://lkml.kernel.org/r/20210722142837.458596338@goodmis.org Reviewed-by: Tom Zanussi Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_hist.c | 46 +++++++++++++++++++++++++++++--- 1 file changed, 42 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index bb466a82b938..9d91b1c06957 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1420,17 +1420,17 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) struct hist_trigger_data *hist_data = elt->map->private_data; unsigned int size = TASK_COMM_LEN; struct hist_elt_data *elt_data; - struct hist_field *key_field; + struct hist_field *hist_field; unsigned int i, n_str; elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL); if (!elt_data) return -ENOMEM; - for_each_hist_key_field(i, hist_data) { - key_field = hist_data->fields[i]; + for_each_hist_field(i, hist_data) { + hist_field = hist_data->fields[i]; - if (key_field->flags & HIST_FIELD_FL_EXECNAME) { + if (hist_field->flags & HIST_FIELD_FL_EXECNAME) { elt_data->comm = kzalloc(size, GFP_KERNEL); if (!elt_data->comm) { kfree(elt_data); @@ -3771,6 +3771,41 @@ static int create_val_field(struct hist_trigger_data *hist_data, return __create_val_field(hist_data, val_idx, file, NULL, field_str, 0); } +static const char *no_comm = "(no comm)"; + +static u64 hist_field_execname(struct hist_field *hist_field, + struct tracing_map_elt *elt, + struct trace_buffer *buffer, + struct ring_buffer_event *rbe, + void *event) +{ + struct hist_elt_data *elt_data; + + if (WARN_ON_ONCE(!elt)) + return (u64)(unsigned long)no_comm; + + elt_data = elt->private_data; + + if (WARN_ON_ONCE(!elt_data->comm)) + return (u64)(unsigned long)no_comm; + + return (u64)(unsigned long)(elt_data->comm); +} + +/* Convert a var that points to common_pid.execname to a string */ +static void update_var_execname(struct hist_field *hist_field) +{ + hist_field->flags = HIST_FIELD_FL_STRING | HIST_FIELD_FL_VAR | + HIST_FIELD_FL_EXECNAME; + hist_field->size = MAX_FILTER_STR_VAL; + hist_field->is_signed = 0; + + kfree_const(hist_field->type); + hist_field->type = "char[]"; + + hist_field->fn = hist_field_execname; +} + static int create_var_field(struct hist_trigger_data *hist_data, unsigned int val_idx, struct trace_event_file *file, @@ -3795,6 +3830,9 @@ static int create_var_field(struct hist_trigger_data *hist_data, ret = __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags); + if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME) + update_var_execname(hist_data->fields[val_idx]); + if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_STRING) hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++;