Merge pull request #1566 from Kijewski/undef_is_null

core: let PIDs begin with 1

core/include/kernel_types.h

@@ -5,10 +5,27 @@
 #include <inttypes.h>
 
 /**
- * @def KERNEL_PID_UNDEF
- * @brief Identifier to detect an invalid PID
+ * @def MAXTHREADS
+ * @brief The maximum number of threads to be scheduled
  */
-#define KERNEL_PID_UNDEF -1
+#ifndef MAXTHREADS
+#define MAXTHREADS 32
+#endif
+
+/**
+ * Canonical identifier for an invalid PID.
+ */
+#define KERNEL_PID_UNDEF 0
+
+/**
+ * The first valid PID (inclusive).
+ */
+#define KERNEL_PID_FIRST (KERNEL_PID_UNDEF + 1)
+
+/**
+ * The last valid PID (inclusive).
+ */
+#define KERNEL_PID_LAST (KERNEL_PID_FIRST + MAXTHREADS - 1)
 
 /**
  * Macro for printing formatter
@@ -16,8 +33,7 @@
 #define PRIkernel_pid PRIi16
 
 /**
- * @brief Unique process identifier
- *
+ * Unique process identifier
  */
 typedef int16_t kernel_pid_t;
 

core/include/sched.h

@@ -84,8 +84,7 @@
 #include "bitarithm.h"
 #include "tcb.h"
 #include "attributes.h"
-
-#define MAXTHREADS 32 /**< the maximum number of threads to be scheduled */
+#include "kernel_types.h"
 
 /**
  * @def SCHED_PRIO_LEVELS
@@ -132,7 +131,7 @@ extern volatile unsigned int sched_context_switch_request;
 /**
  *  Thread table
  */
-extern volatile tcb_t *sched_threads[MAXTHREADS];
+extern volatile tcb_t *sched_threads[KERNEL_PID_LAST + 1];
 
 /**
  *  Currently active thread
@@ -168,7 +167,7 @@ typedef struct {
 /**
  *  Thread statistics table
  */
-extern schedstat sched_pidlist[MAXTHREADS];
+extern schedstat sched_pidlist[KERNEL_PID_LAST + 1];
 
 /**
  *  @brief  Register a callback that will be called on every scheduler run

core/sched.c

@@ -40,7 +40,7 @@ volatile int sched_num_threads = 0;
 
 volatile unsigned int sched_context_switch_request;
 
-volatile tcb_t *sched_threads[MAXTHREADS];
+volatile tcb_t *sched_threads[KERNEL_PID_LAST + 1];
 volatile tcb_t *sched_active_thread;
 
 volatile kernel_pid_t sched_active_pid = KERNEL_PID_UNDEF;
@@ -50,7 +50,7 @@ static uint32_t runqueue_bitcache = 0;
 
 #if SCHEDSTATISTICS
 static void (*sched_cb) (uint32_t timestamp, uint32_t value) = NULL;
-schedstat sched_pidlist[MAXTHREADS];
+schedstat sched_pidlist[KERNEL_PID_LAST + 1];
 #endif
 
 void sched_run(void)

core/thread.c

@@ -34,7 +34,7 @@
 
 volatile tcb_t *thread_get(kernel_pid_t pid)
 {
-    if ((pid != KERNEL_PID_UNDEF) && (0 <= pid) && (pid < MAXTHREADS)) {
+    if ((pid != KERNEL_PID_UNDEF) && (KERNEL_PID_FIRST <= pid) && (pid <= KERNEL_PID_LAST)) {
         return sched_threads[pid];
     }
     return NULL;
@@ -153,19 +153,14 @@ kernel_pid_t thread_create(char *stack, int stacksize, char priority, int flags,
         dINT();
     }
 
-    kernel_pid_t pid = 0;
-
-    while (pid < MAXTHREADS) {
-        if (sched_threads[pid] == NULL) {
-            sched_threads[pid] = cb;
-            cb->pid = pid;
+    kernel_pid_t pid = KERNEL_PID_UNDEF;
+    for (kernel_pid_t i = KERNEL_PID_FIRST; i <= KERNEL_PID_LAST; ++i) {
+        if (sched_threads[i] == NULL) {
+            pid = i;
             break;
         }
-
-        pid++;
     }
-
-    if (pid == MAXTHREADS) {
+    if (pid == KERNEL_PID_UNDEF) {
         DEBUG("thread_create(): too many threads!\n");
 
         if (!inISR()) {
@@ -175,6 +170,9 @@ kernel_pid_t thread_create(char *stack, int stacksize, char priority, int flags,
         return -EOVERFLOW;
     }
 
+    sched_threads[pid] = cb;
+
+    cb->pid = pid;
     cb->sp = thread_stack_init(function, arg, stack, stacksize);
     cb->stack_start = stack;
 

cpu/x86/x86_hwtimer.c

@@ -91,7 +91,7 @@ static void flip_periodic_interrupt_called(uint8_t reg_c)
 static void measure_nop_nop_nops_per_tick(void)
 {
     x86_rtc_set_periodic_callback(flip_periodic_interrupt_called);
-    x86_rtc_set_periodic(TICK_HZ_REG_A, 0, 0, true);
+    x86_rtc_set_periodic(TICK_HZ_REG_A, 0, KERNEL_PID_FIRST, true);
     for (unsigned i = 0; i < NNN_TICK_ITERATIONS; ++i) {
         periodic_interrupt_called = false;
 
@@ -132,7 +132,7 @@ static void update_cb(uint8_t reg_c)
 static void init_bases(void)
 {
     x86_rtc_set_periodic_callback(update_cb);
-    x86_rtc_set_periodic(RTC_REG_A_HZ_2, 0, 0, true);
+    x86_rtc_set_periodic(RTC_REG_A_HZ_2, 0, KERNEL_PID_FIRST, true);
 
     eINT();
     periodic_interrupt_called = false;

sys/ps/ps.c

@@ -21,6 +21,7 @@
 #include "hwtimer.h"
 #include "sched.h"
 #include "tcb.h"
+#include "kernel_types.h"
 
 /* list of states copied from tcb.h */
 const char *state_names[] = {
@@ -40,7 +41,6 @@ const char *state_names[] = {
 void thread_print_all(void)
 {
     const char queued_name[] = {'_', 'Q'};
-    int i;
 #ifdef DEVELHELP
     int overall_stacksz = 0, overall_used = 0;
 #endif
@@ -56,7 +56,7 @@ void thread_print_all(void)
            "\n"
            , "name", "state");
 
-    for (i = 0; i < MAXTHREADS; i++) {
+    for (kernel_pid_t i = KERNEL_PID_FIRST; i <= KERNEL_PID_LAST; i++) {
         tcb_t *p = (tcb_t *)sched_threads[i];
 
         if (p != NULL) {