Fix RR scheduler and mutex/cond

Makefile

@@ -39,7 +39,7 @@ deps := $(OBJS:%.o=.%.o.d)
 
 .PHONY: all check clean distclean
 
-all: $(CMSIS)/$(PLAT) $(NAME).lds $(NAME).bin
+all: FORCE $(CMSIS)/$(PLAT) $(NAME).lds $(NAME).bin
 
 # generic build rules
 include mk/flags.mk
@@ -73,3 +73,5 @@ distclean: clean
 include platform/$(PLAT)/build.mk
 
 -include $(deps)
+
+FORCE:

README.md

@@ -15,3 +15,17 @@ $ python -m tests
 # Run partial test with command line tools
 $ python -m tests fs_1 cond_2
 ```
+
+## Makefile
+
+You can switch scheduler by makefile flags:
+
+```
+# Using bitmap scheduler
+
+$ make SCHED=BITMAP
+
+# Using RR scheduler
+
+$ make SCHED=RR
+```

include/kernel/sched.h

@@ -18,13 +18,13 @@ struct thread_info;
 #define SCHED_OPT_TICK 3
 
 struct sched {
- int (*init)(void);
+ int (*init)(struct thread_info *thread);
  int (*enqueue)(struct thread_info *thread);
  int (*dequeue)(struct thread_info *thread);
  int (*elect)(int switch_type);
 };
 
-int sched_select(int sched_type);
+int sched_select(int sched_type, struct thread_info *thread);
 int sched_enqueue(struct thread_info *thread);
 int sched_dequeue(struct thread_info *thread);
 int sched_elect(int flags);

include/kernel/thread.h

@@ -35,6 +35,8 @@ struct thread_info {
  struct list_head ti_list; /* global list of threads */
  struct list_head ti_q; /* shared by sched runq, mutex waitq, thread joinq */
 
+ int ti_queued; /* in runqueue */
+
  /* http://www.domaigne.com/blog/computing/joinable-and-detached-threads/ */
  void *ti_retval;
  int ti_detached;

kernel/cond.c

@@ -26,6 +26,7 @@ int sys_pthread_cond_wait(pthread_cond_t *cond, kernel_mutex_t *mutex)
  CURRENT_THREAD_INFO(curr_thread);
  curr_thread->ti_private = cond;
  curr_thread->ti_state = THREAD_STATE_BLOCKED;
+ sched_dequeue(curr_thread);
  list_add_tail(&curr_thread->ti_q, &cond_head);
  sys_pthread_mutex_unlock(mutex);
 

kernel/main.c

@@ -45,6 +45,11 @@ void init_IRQ(void);
 struct task_info idle_task;
 struct task_info main_task;
 
+/* Select scheduler */
+#ifndef SCHED_CLASS
+#define SCHED_CLASS SCHED_CLASS_BITMAP
+#endif
+
 void print_version(void)
 {
  char buf[] = {0, 0};
@@ -130,9 +135,6 @@ struct thread_info *start_kernel(void)
  show_page_bitmap(); // init_pages();
  kmem_cache_init();
 
- /* select a scheduling policy */
- sched_select(SCHED_CLASS_BITMAP);
-
  /* idle_thread is not added to the runqueue */
  task_init(&idle_task);
  thread_idle =
@@ -156,6 +158,9 @@ struct thread_info *start_kernel(void)
  printk("Created main_thread at <%p> with priority=%d\n", thread_main,
  thread_main->ti_priority);
 
+ /* select a scheduling policy */
+ sched_select(SCHED_CLASS, thread_main);
+
  /* Reclaim the early-stack physical memory. In the current context, no
  * page allocation after this point are allowed. */
  printk("Reclaim early stack's physical memory (%d Bytes, order=%d).\n",

kernel/mutex.c

@@ -17,6 +17,7 @@ int sys_pthread_mutex_lock(kernel_mutex_t *mutex)
  CURRENT_THREAD_INFO(curr_thread);
  curr_thread->ti_private = mutex;
  curr_thread->ti_state = THREAD_STATE_BLOCKED;
+ sched_dequeue(curr_thread);
  list_add_tail(&curr_thread->ti_q, &mutex_head);
  sched_elect(SCHED_OPT_NONE);
 

kernel/sched.c

@@ -6,20 +6,24 @@ extern const struct sched sched_bitmap;
 
 static const struct sched *sched;
 
-int sched_select(int sched_type)
+int sched_select(int sched_type, struct thread_info *thread)
 {
+ printk("Scheduler: ");
  switch (sched_type) {
  case SCHED_CLASS_RR:
+ printk("Round-Robin\n");
  sched = &sched_rr;
  break;
  case SCHED_CLASS_BITMAP:
+ printk("Bitmap\n");
  sched = &sched_bitmap;
  break;
  default:
+ printk("Unknown");
  return -1;
  }
 
- return sched->init();
+ return sched->init(thread);
 }
 
 int sched_enqueue(struct thread_info *thread)

kernel/sched/bitmap.c

@@ -18,7 +18,7 @@ static struct {
  .expire = &_expire,
 };
 
-static int sched_bitmap_init(void)
+static int sched_bitmap_init(__unused struct thread_info *thread)
 {
  INIT_BITMAP(sched_struct.active);
  INIT_BITMAP(sched_struct.expire);

kernel/sched/rr.c

@@ -7,74 +7,61 @@
 static LIST_HEAD(rr_runq);
 extern struct thread_info *thread_idle;
 
-int sched_rr_init(void)
+int sched_rr_init(struct thread_info *thread)
 {
+ if (thread)
+ sched_rr_enqueue(thread);
  return 0;
 }
 
-static struct thread_info *find_next_thread(struct thread_info *thread)
+static struct thread_info *find_next_thread(void)
 {
- if (list_is_last(&thread->ti_q, &rr_runq))
- return list_first_entry(&rr_runq, struct thread_info, ti_q);
-
- return list_next_entry(thread, ti_q);
+ return list_first_entry(&rr_runq, struct thread_info, ti_q);
 }
 
 int sched_rr_enqueue(struct thread_info *thread)
 {
- list_add(&thread->ti_q, &rr_runq);
+ if (thread->ti_queued)
+ return -1;
+
+ list_add_tail(&thread->ti_q, &rr_runq);
+ thread->ti_queued = 1;
 
  return 0;
 }
 
 int sched_rr_dequeue(struct thread_info *thread)
 {
- CURRENT_THREAD_INFO(current);
+ if (!thread->ti_queued)
+ return -1;
 
- if (current == thread) {
- struct thread_info *next = thread_idle;
- if (!list_is_singular(&rr_runq)) {
- next = find_next_thread(current);
- }
- list_del(&thread->ti_q);
- thread_restore(next); // FIXME: rename to switch_to_no_save
- } else {
- list_del(&thread->ti_q);
- }
+ list_del(&thread->ti_q);
+ thread->ti_queued = 0;
 
  return 0;
 }
 
-/* This function is used when the runqueue has been modified externally, and it
- is not possible to fetch the next thread. */
-static int sched_rr_elect_reset(void)
+void sched_rr_requeue(struct thread_info *thread)
 {
- CURRENT_THREAD_INFO(current);
- struct thread_info *next = thread_idle;
-
- if (!list_empty(&rr_runq))
- next = list_first_entry(&rr_runq, struct thread_info, ti_q);
- switch_to(next, current);
-
- return 0;
+ sched_rr_dequeue(thread);
+ sched_rr_enqueue(thread);
 }
 
-int sched_rr_elect(int switch_type)
+int sched_rr_elect(__unused int switch_type)
 {
  CURRENT_THREAD_INFO(current);
  struct thread_info *next;
 
- if (switch_type & SCHED_OPT_RESET)
- return sched_rr_elect_reset();
-
  if (list_empty(&rr_runq)) {
- // go to thread idle.
- next = thread_idle;
- } else {
- next = find_next_thread(current);
+ switch_to(thread_idle, current);
+ return -1;
  }
 
- /* keep running the previous thread */
+ /* XXX: Will RR stuck inside the loop? */
+ while ((next = find_next_thread()) == current && !list_is_singular(&rr_runq))
+ sched_rr_requeue(next);
+
+ /* Shortcut if next is current */
  if (next == current)
  return -1;
 

libc/v7m-pthread.S

@@ -22,10 +22,10 @@ ENTRY(pthread_mutex_lock)
  bne 0b
  dmb @ ARMv7-M ARM, A3.4.6
  movs r0, #0 @ it also update EQ flag
-1: itt ne
- movne r1, #SYS_PTHREAD_MUTEX_LOCK
- svcne #1
- bx lr
+1: beq 2f
+ mov r1, #SYS_PTHREAD_MUTEX_LOCK
+ svc #1
+2: bx lr
 ENDPROC(pthread_mutex_lock)
 
  @ int pthread_mutex_trylock(pthread_mutex_t *mutex)
@@ -38,9 +38,9 @@ ENTRY(pthread_mutex_trylock)
  teq r1, #0 @ 'strex' success?
  bne 1f
  movs r0, #0 @ it also update EQ flag
-1: it ne
- movne r0, #-1
- bx lr
+1: beq 2f
+ mov r0, #-1
+2: bx lr
 ENDPROC(pthread_mutex_trylock)
 
  @ int pthread_mutex_unlock(pthread_mutex_t *mutex)
@@ -54,8 +54,8 @@ ENTRY(pthread_mutex_unlock)
  bne 0b
  dmb @ ARMv7-M ARM, A3.4.6
  movs r0, #0 @ it also update EQ flag
-1: itt ne
- movne r1, #SYS_PTHREAD_MUTEX_UNLOCK
- svcne #1
- bx lr
-ENDPROC(pthread_mutex_unlock)
+1: beq 2f
+ mov r1, #SYS_PTHREAD_MUTEX_UNLOCK
+ svc #1
+2: bx lr
+ENDPROC(pthread_mutex_lock)

mk/flags.mk

@@ -25,6 +25,16 @@ CFLAGS += \
 CFLAGS += \
  -D CONFIG_KERNEL_STACK_CHECKING
 
+# Scheduler
+ifdef SCHED
+ CFLAGS += -D SCHED_CLASS=SCHED_CLASS_$(SCHED)
+RESCHED:
+ $(VECHO) " RM\t\tkernel/main.o\n"
+ $(Q)$(RM) kernel/main.o
+
+FORCE: RESCHED
+endif
+
 LDFLAGS += \
  -nostartfiles -specs=nano.specs \
  -Wl,-Map=$(NAME).map -Wl,-Tpiko.lds -Wl,--gc-sections