[PATCH] perf sched: parse task state from tracepoint print format

[Ze Gao]

As of this writing, we use prev_state to report task state,
which relies on both the task state macros and
TASK_STATE_TO_CHAR_STR in kernel to interpret its actual
meaning. In this way, perf gets broken literally each time
TASK_STATE_TO_CHAR_STR changes as kernel evolves. Counting
on TASK_STATE_TO_CHAR_STR gurantees no backward compatibilty.

To fix this, we build the state char map from the print
format parsed from perf.data on the fly and removes
dependencies on these internal kernel definitions.

Note that we provide an intended helper get_task_prev_state()
for extracting task state from perf record and passing task
state in char elsewhere, which helps to eliminate the need to
know task state macros further.

Signed-off-by: Ze Gao <zegao@xxxxxxxxxxx>
---
 tools/perf/builtin-sched.c | 126 +++++++++++++++++++++++--------------
 1 file changed, 80 insertions(+), 46 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 9ab300b6f131..9366bc0a991d 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -52,6 +52,10 @@
 #define SYM_LEN			129
 #define MAX_PID			1024000
 
+#define TASK_STATE_MAX 16
+static char state_to_char[TASK_STATE_MAX];
+static unsigned int num_sleep_states = 0;
+
 static const char *cpu_list;
 static DECLARE_BITMAP(cpu_bitmap, MAX_NR_CPUS);
 
@@ -92,24 +96,6 @@ struct sched_atom {
 	struct task_desc	*wakee;
 };
 
-#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKWP"
-
-/* task state bitmask, copied from include/linux/sched.h */
-#define TASK_RUNNING		0
-#define TASK_INTERRUPTIBLE	1
-#define TASK_UNINTERRUPTIBLE	2
-#define __TASK_STOPPED		4
-#define __TASK_TRACED		8
-/* in tsk->exit_state */
-#define EXIT_DEAD		16
-#define EXIT_ZOMBIE		32
-#define EXIT_TRACE		(EXIT_ZOMBIE | EXIT_DEAD)
-/* in tsk->state again */
-#define TASK_DEAD		64
-#define TASK_WAKEKILL		128
-#define TASK_WAKING		256
-#define TASK_PARKED		512
-
 enum thread_state {
 	THREAD_SLEEPING = 0,
 	THREAD_WAIT_CPU,
@@ -266,7 +252,7 @@ struct thread_runtime {
 	u64 total_preempt_time;
 	u64 total_delay_time;
 
-	int last_state;
+	char last_state;
 
 	char shortname[3];
 	bool comm_changed;
@@ -436,7 +422,7 @@ static void add_sched_event_wakeup(struct perf_sched *sched, struct task_desc *t
 }
 
 static void add_sched_event_sleep(struct perf_sched *sched, struct task_desc *task,
-				  u64 timestamp, u64 task_state __maybe_unused)
+				  u64 timestamp, char task_state __maybe_unused)
 {
 	struct sched_atom *event = get_new_event(task, timestamp);
 
@@ -851,6 +837,72 @@ replay_wakeup_event(struct perf_sched *sched,
 	return 0;
 }
 
+static struct tep_print_arg* task_state_print_flag(struct tep_event *event)
+{
+       struct tep_print_arg* args = event->print_fmt.args;
+
+       while(args)
+       {
+               if (args->type == TEP_PRINT_FLAGS)
+                       return args;
+               if (args->type == TEP_PRINT_OP) {
+                       args = args->op.right;
+                       args = args->op.left;
+                       continue;
+               }
+               args = args->next;
+       }
+       return NULL;
+}
+
+static void __parse_print_flag(struct tep_print_flag_sym *field)
+{
+
+       long val = strtol(field->value, NULL, 0);
+       unsigned int bit = val ? ffs(val) : 0;
+
+       state_to_char[bit] = field->str[0];
+       num_sleep_states++;
+       if(num_sleep_states > TASK_STATE_MAX - 1) {
+               pr_warning("too many states parsed, possibly bad format\n");
+               return;
+       }
+       if (field->next) {
+               __parse_print_flag(field->next);
+       }
+}
+
+static inline void parse_print_flag(struct tep_print_arg* args)
+{
+       __parse_print_flag(args->flags.flags);
+}
+
+static void build_task_state_arr(struct tep_event *event)
+{
+       struct tep_print_arg* args;
+
+       args = task_state_print_flag(event);
+       if (!args)
+               pr_warning("print flag not found, possibly bad format\n");
+       else
+               parse_print_flag(args);
+}
+
+static inline char get_prev_task_state(struct evsel *evsel,
+		struct perf_sample *sample)
+{
+	int prev_state = evsel__intval(evsel, sample, "prev_state");
+	unsigned int bit = prev_state ? ffs(prev_state) : 0;
+	char state;
+
+	if(!num_sleep_states)
+		build_task_state_arr(evsel->tp_format);
+
+	state = (!bit || bit > num_sleep_states) ? 'R' : state_to_char[bit];
+
+	return state;
+}
+
 static int replay_switch_event(struct perf_sched *sched,
 			       struct evsel *evsel,
 			       struct perf_sample *sample,
@@ -860,7 +912,7 @@ static int replay_switch_event(struct perf_sched *sched,
 		   *next_comm  = evsel__strval(evsel, sample, "next_comm");
 	const u32 prev_pid = evsel__intval(evsel, sample, "prev_pid"),
 		  next_pid = evsel__intval(evsel, sample, "next_pid");
-	const u64 prev_state = evsel__intval(evsel, sample, "prev_state");
+	const char prev_state = get_prev_task_state(evsel, sample);
 	struct task_desc *prev, __maybe_unused *next;
 	u64 timestamp0, timestamp = sample->time;
 	int cpu = sample->cpu;
@@ -1050,12 +1102,6 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
 	return 0;
 }
 
-static char sched_out_state(u64 prev_state)
-{
-	const char *str = TASK_STATE_TO_CHAR_STR;
-
-	return str[prev_state];
-}
 
 static int
 add_sched_out_event(struct work_atoms *atoms,
@@ -1132,7 +1178,7 @@ static int latency_switch_event(struct perf_sched *sched,
 {
 	const u32 prev_pid = evsel__intval(evsel, sample, "prev_pid"),
 		  next_pid = evsel__intval(evsel, sample, "next_pid");
-	const u64 prev_state = evsel__intval(evsel, sample, "prev_state");
+	const char prev_state = get_prev_task_state(evsel, sample);
 	struct work_atoms *out_events, *in_events;
 	struct thread *sched_out, *sched_in;
 	u64 timestamp0, timestamp = sample->time;
@@ -1168,7 +1214,7 @@ static int latency_switch_event(struct perf_sched *sched,
 			goto out_put;
 		}
 	}
-	if (add_sched_out_event(out_events, sched_out_state(prev_state), timestamp))
+	if (add_sched_out_event(out_events, prev_state, timestamp))
 		return -1;
 
 	in_events = thread_atoms_search(&sched->atom_root, sched_in, &sched->cmp_pid);
@@ -2033,24 +2079,12 @@ static void timehist_header(struct perf_sched *sched)
 	printf("\n");
 }
 
-static char task_state_char(struct thread *thread, int state)
-{
-	static const char state_to_char[] = TASK_STATE_TO_CHAR_STR;
-	unsigned bit = state ? ffs(state) : 0;
-
-	/* 'I' for idle */
-	if (thread__tid(thread) == 0)
-		return 'I';
-
-	return bit < sizeof(state_to_char) - 1 ? state_to_char[bit] : '?';
-}
-
 static void timehist_print_sample(struct perf_sched *sched,
 				  struct evsel *evsel,
 				  struct perf_sample *sample,
 				  struct addr_location *al,
 				  struct thread *thread,
-				  u64 t, int state)
+				  u64 t, char state)
 {
 	struct thread_runtime *tr = thread__priv(thread);
 	const char *next_comm = evsel__strval(evsel, sample, "next_comm");
@@ -2091,7 +2125,7 @@ static void timehist_print_sample(struct perf_sched *sched,
 	print_sched_time(tr->dt_run, 6);
 
 	if (sched->show_state)
-		printf(" %5c ", task_state_char(thread, state));
+		printf(" %5c ", thread->tid == 0 ? 'I' : state);
 
 	if (sched->show_next) {
 		snprintf(nstr, sizeof(nstr), "next: %s[%d]", next_comm, next_pid);
@@ -2163,9 +2197,9 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
 		else if (r->last_time) {
 			u64 dt_wait = tprev - r->last_time;
 
-			if (r->last_state == TASK_RUNNING)
+			if (r->last_state == 'R')
 				r->dt_preempt = dt_wait;
-			else if (r->last_state == TASK_UNINTERRUPTIBLE)
+			else if (r->last_state == 'D')
 				r->dt_iowait = dt_wait;
 			else
 				r->dt_sleep = dt_wait;
@@ -2590,7 +2624,7 @@ static int timehist_sched_change_event(struct perf_tool *tool,
 	struct thread_runtime *tr = NULL;
 	u64 tprev, t = sample->time;
 	int rc = 0;
-	int state = evsel__intval(evsel, sample, "prev_state");
+	const char state = get_prev_task_state(evsel, sample);
 
 	addr_location__init(&al);
 	if (machine__resolve(machine, &al, sample) < 0) {
-- 
2.41.0