posix: Add posix CLOCK_THREAD_CPUTIME_ID support

Add posix 'CLOCK_THREAD_CPUTIME_ID' support to measure the
total CPU execution time of the current thread.

Signed-off-by: James Roy <rruuaanng@outlook.com>

Author: rruuaanng

lib/posix/options/Kconfig.timer

@@ -17,6 +17,8 @@ if POSIX_TIMERS
 
 config POSIX_THREAD_CPUTIME
 	bool "POSIX per-thread CPU-time clocks"
+	select THREAD_RUNTIME_STATS
+	select SCHED_THREAD_USAGE_ANALYSIS
 	help
 	  This enables CLOCK_THREAD_CPUTIME_ID.
 

lib/posix/options/clock.c

@@ -43,6 +43,23 @@ int z_impl___posix_clock_get_base(clockid_t clock_id, struct timespec *base)
 			*base = rt_clock_base;
 		}
 		break;
+#ifdef CONFIG_POSIX_THREAD_CPUTIME
+	case CLOCK_THREAD_CPUTIME_ID: {
+		uint64_t ns;
+		k_thread_runtime_stats_t stats;
+		k_tid_t thread = k_current_get();
+
+		if (!k_thread_runtime_stats_is_enabled(thread)) {
+			errno = EINVAL;
+			return -1;
+		}
+		k_thread_runtime_stats_get(thread, &stats);
+		ns = k_cyc_to_ns_floor64(stats.execution_cycles);
+		base->tv_sec = ns / NSEC_PER_SEC;
+		base->tv_nsec = ns % NSEC_PER_SEC;
+		break;
+	}
+#endif /* CONFIG_POSIX_THREAD_CPUTIME */
 
 	default:
 		errno = EINVAL;
@@ -75,6 +92,13 @@ int clock_gettime(clockid_t clock_id, struct timespec *ts)
 		(void)__posix_clock_get_base(clock_id, &base);
 		break;
 
+#ifdef CONFIG_POSIX_THREAD_CPUTIME
+	case CLOCK_THREAD_CPUTIME_ID:
+		(void)__posix_clock_get_base(clock_id, &base);
+		*ts = base;
+		return 0;
+#endif /* CONFIG_POSIX_THREAD_CPUTIME */
+
 	default:
 		errno = EINVAL;
 		return -1;