rockbox/firmware/thread.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Ulf Ralberg
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "config.h"
#include <stdbool.h>
#include "thread.h"
#include "panic.h"
#include "sprintf.h"
#include "system.h"
#include "kernel.h"
#include "cpu.h"
#include "string.h"
#ifdef RB_PROFILE
#include <profile.h>
#endif

#if NUM_CORES > 1
# define IF_COP2(x) x
#else
# define IF_COP2(x) CURRENT_CORE
#endif

#define DEADBEEF ((unsigned int)0xdeadbeef)
/* Cast to the the machine int type, whose size could be < 4. */

struct core_entry cores[NUM_CORES] IBSS_ATTR;
struct thread_entry threads[MAXTHREADS] IBSS_ATTR;
#ifdef HAVE_SCHEDULER_BOOSTCTRL
static int boosted_threads IBSS_ATTR;
#endif

/* Define to enable additional checks for blocking violations etc. */
#define THREAD_EXTRA_CHECKS 0

static const char main_thread_name[] = "main";

extern int stackbegin[];
extern int stackend[];

/* Conserve IRAM
static void add_to_list(struct thread_entry **list,
                        struct thread_entry *thread) ICODE_ATTR;
static void remove_from_list(struct thread_entry **list,
                             struct thread_entry *thread) ICODE_ATTR;
*/

void switch_thread(bool save_context, struct thread_entry **blocked_list)
    ICODE_ATTR;

static inline void store_context(void* addr) __attribute__ ((always_inline));
static inline void load_context(const void* addr)
    __attribute__ ((always_inline));
static inline void core_sleep(void) __attribute__((always_inline));

#if defined(CPU_ARM)
/*---------------------------------------------------------------------------
 * Start the thread running and terminate it if it returns
 *---------------------------------------------------------------------------
 */
static void start_thread(void) __attribute__((naked,used));
static void start_thread(void)
{
    /* r0 = context */
    asm volatile (
        "ldr    sp, [r0, #32]          \n" /* Load initial sp */
        "ldr    r4, [r0, #40]          \n" /* start in r4 since it's non-volatile */
        "mov    r1, #0                 \n" /* Mark thread as running */
        "str    r1, [r0, #40]          \n"
#if NUM_CORES > 1
        "ldr    r0, =invalidate_icache \n" /* Invalidate this core's cache. */
        "mov    lr, pc                 \n" /* This could be the first entry into */
        "bx     r0                     \n" /* plugin or codec code for this core. */
#endif
        "mov    lr, pc                 \n" /* Call thread function */
        "bx     r4                     \n"
        "mov    r0, #0                 \n" /* remove_thread(NULL) */
        "ldr    pc, =remove_thread     \n"
        ".ltorg                        \n" /* Dump constant pool */
    ); /* No clobber list - new thread doesn't care */
}

/*---------------------------------------------------------------------------
 * Store non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void store_context(void* addr)
{
    asm volatile(
        "stmia  %0, { r4-r11, sp, lr } \n"
        : : "r" (addr)
    );
}

/* For startup, place context pointer in r4 slot, start_thread pointer in r5
 * slot, and thread function pointer in context.start. See load_context for
 * what happens when thread is initially going to run. */
#define THREAD_STARTUP_INIT(core, thread, function) \
    ({ (thread)->context.r[0] = (unsigned int)&(thread)->context,  \
       (thread)->context.r[1] = (unsigned int)start_thread, \
       (thread)->context.start = (void *)function; })

static inline void load_context(const void* addr)
{
    asm volatile(
        "ldr     r0, [%0, #40]          \n" /* Load start pointer */
        "cmp     r0, #0                 \n" /* Check for NULL */
        "ldmneia %0, { r0, pc }         \n" /* If not already running, jump to start */ 
        "ldmia   %0, { r4-r11, sp, lr } \n" /* Load regs r4 to r14 from context */
        : : "r" (addr) : "r0" /* only! */
    );
}

#if defined (CPU_PP)

#if NUM_CORES > 1
extern int cpu_idlestackbegin[];
extern int cpu_idlestackend[];
extern int cop_idlestackbegin[];
extern int cop_idlestackend[];
static int * const idle_stacks[NUM_CORES] NOCACHEDATA_ATTR =
{
    [CPU] = cpu_idlestackbegin,
    [COP] = cop_idlestackbegin
};
#endif /* NUM_CORES */

static inline void core_sleep(void)
{
    /* This should sleep the CPU. It appears to wake by itself on
       interrupts */
    if (CURRENT_CORE == CPU)
        CPU_CTL = PROC_SLEEP;
    else
        COP_CTL = PROC_SLEEP;
}

#if NUM_CORES > 1
/*---------------------------------------------------------------------------
 * Switches to a stack that always resides in the Rockbox core.
 *
 * Needed when a thread suicides on a core other than the main CPU since the
 * stack used when idling is the stack of the last thread to run. This stack
 * may not reside in the core in which case the core will continue to use a
 * stack from an unloaded module until another thread runs on it.
 *---------------------------------------------------------------------------
 */
static inline void switch_to_idle_stack(const unsigned int core)
{
    asm volatile (
        "str  sp, [%0] \n" /* save original stack pointer on idle stack */
        "mov  sp, %0   \n" /* switch stacks */
        : : "r"(&idle_stacks[core][IDLE_STACK_WORDS-1]));
    (void)core;
}
#endif /* NUM_CORES */

#elif CONFIG_CPU == S3C2440
static inline void core_sleep(void)
{
    int i;
    CLKCON |= (1 << 2); /* set IDLE bit */
    for(i=0; i<10; i++); /* wait for IDLE */
    CLKCON &= ~(1 << 2); /* reset IDLE bit when wake up */
}
#else
static inline void core_sleep(void)
{

}
#endif

#elif defined(CPU_COLDFIRE)
/*---------------------------------------------------------------------------
 * Start the thread running and terminate it if it returns
 *---------------------------------------------------------------------------
 */
void start_thread(void); /* Provide C access to ASM label */
static void __start_thread(void) __attribute__((used));
static void __start_thread(void)
{
    /* a0=macsr, a1=context */
    asm volatile (
    "start_thread:             \n" /* Start here - no naked attribute */
        "move.l  %a0, %macsr   \n" /* Set initial mac status reg */
        "lea.l   48(%a1), %a1  \n"
        "move.l  (%a1)+, %sp   \n" /* Set initial stack */
        "move.l  (%a1), %a2    \n" /* Fetch thread function pointer */
        "clr.l   (%a1)         \n" /* Mark thread running */
        "jsr     (%a2)         \n" /* Call thread function */
        "clr.l   -(%sp)        \n" /* remove_thread(NULL) */
        "jsr     remove_thread \n"
    );
}

/* Set EMAC unit to fractional mode with saturation for each new thread,
 * since that's what'll be the most useful for most things which the dsp
 * will do. Codecs should still initialize their preferred modes
 * explicitly. Context pointer is placed in d2 slot and start_thread
 * pointer in d3 slot. thread function pointer is placed in context.start.
 * See load_context for what happens when thread is initially going to
 * run.
 */
#define THREAD_STARTUP_INIT(core, thread, function) \
    ({ (thread)->context.macsr = EMAC_FRACTIONAL | EMAC_SATURATE, \
       (thread)->context.d[0] = (unsigned int)&(thread)->context, \
       (thread)->context.d[1] = (unsigned int)start_thread,       \
       (thread)->context.start = (void *)(function); })

/*---------------------------------------------------------------------------
 * Store non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void store_context(void* addr)
{
    asm volatile (
        "move.l  %%macsr,%%d0                  \n"
        "movem.l %%d0/%%d2-%%d7/%%a2-%%a7,(%0) \n"
        : : "a" (addr) : "d0" /* only! */
    );
}

/*---------------------------------------------------------------------------
 * Load non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void load_context(const void* addr)
{
    asm volatile (
        "move.l  52(%0), %%d0                   \n"  /* Get start address */
        "beq.b   1f                             \n"  /* NULL -> already running */
        "movem.l (%0), %%a0-%%a2                \n"  /* a0=macsr, a1=context, a2=start_thread */
        "jmp     (%%a2)                         \n"  /* Start the thread */
    "1:                                         \n"
        "movem.l (%0), %%d0/%%d2-%%d7/%%a2-%%a7 \n"  /* Load context */
        "move.l  %%d0, %%macsr                  \n"
        : : "a" (addr) : "d0" /* only! */
    );
}

static inline void core_sleep(void)
{
    asm volatile ("stop #0x2000");
}

/* Set EMAC unit to fractional mode with saturation for each new thread,
   since that's what'll be the most useful for most things which the dsp
   will do. Codecs should still initialize their preferred modes
   explicitly. */
#define THREAD_CPU_INIT(core, thread) \
    ({ (thread)->context.macsr = EMAC_FRACTIONAL | EMAC_SATURATE; })

#elif CONFIG_CPU == SH7034
/*---------------------------------------------------------------------------
 * Start the thread running and terminate it if it returns
 *---------------------------------------------------------------------------
 */
void start_thread(void); /* Provide C access to ASM label */
static void __start_thread(void) __attribute__((used));
static void __start_thread(void)
{
    /* r8 = context */
    asm volatile (
    "_start_thread:            \n" /* Start here - no naked attribute */
        "mov.l  @(4, r8), r0   \n" /* Fetch thread function pointer */
        "mov.l  @(28, r8), r15 \n" /* Set initial sp */
        "mov    #0, r1         \n" /* Start the thread */
        "jsr    @r0            \n"
        "mov.l  r1, @(36, r8)  \n" /* Clear start address */
        "mov.l  1f, r0         \n" /* remove_thread(NULL) */
        "jmp    @r0            \n"
        "mov    #0, r4         \n"
    "1:                        \n"
        ".long  _remove_thread \n"
    );
}

/* Place context pointer in r8 slot, function pointer in r9 slot, and
 * start_thread pointer in context_start */
#define THREAD_STARTUP_INIT(core, thread, function) \
    ({ (thread)->context.r[0] = (unsigned int)&(thread)->context, \
       (thread)->context.r[1] = (unsigned int)(function),         \
       (thread)->context.start = (void*)start_thread; })

/*---------------------------------------------------------------------------
 * Store non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void store_context(void* addr)
{
    asm volatile (
        "add     #36, %0   \n" /* Start at last reg. By the time routine */
        "sts.l   pr, @-%0  \n" /* is done, %0 will have the original value */
        "mov.l   r15,@-%0  \n"
        "mov.l   r14,@-%0  \n"
        "mov.l   r13,@-%0  \n"
        "mov.l   r12,@-%0  \n"
        "mov.l   r11,@-%0  \n"
        "mov.l   r10,@-%0  \n"
        "mov.l   r9, @-%0  \n"
        "mov.l   r8, @-%0  \n"
        : : "r" (addr)
    );
}

/*---------------------------------------------------------------------------
 * Load non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void load_context(const void* addr)
{
    asm volatile (
        "mov.l  @(36, %0), r0 \n" /* Get start address */
        "tst    r0, r0        \n"
        "bt     .running      \n" /* NULL -> already running */
        "jmp    @r0           \n" /* r8 = context */
    ".running:                \n"
        "mov.l  @%0+, r8      \n" /* Executes in delay slot and outside it */
        "mov.l  @%0+, r9      \n"
        "mov.l  @%0+, r10     \n"
        "mov.l  @%0+, r11     \n"
        "mov.l  @%0+, r12     \n"
        "mov.l  @%0+, r13     \n"
        "mov.l  @%0+, r14     \n"
        "mov.l  @%0+, r15     \n"
        "lds.l  @%0+, pr      \n"
        : : "r" (addr) : "r0" /* only! */
    );
}

static inline void core_sleep(void)
{
    and_b(0x7F, &SBYCR);
    asm volatile ("sleep");
}

#endif

#ifndef THREAD_CPU_INIT
/* No cpu specific init - make empty */
#define THREAD_CPU_INIT(core, thread)
#endif

#if THREAD_EXTRA_CHECKS
static void thread_panicf(const char *msg, struct thread_entry *thread)
{
#if NUM_CORES > 1
    const unsigned int core = thread->core;
#endif
    static char name[32];
    thread_get_name(name, 32, thread);
    panicf ("%s %s" IF_COP(" (%d)"), msg, name IF_COP(, core));
}
static void thread_stkov(struct thread_entry *thread)
{
    thread_panicf("Stkov", thread);
}
#define THREAD_PANICF(msg, thread) \
    thread_panicf(msg, thread)
#define THREAD_ASSERT(exp, msg, thread) \
    ({ if (!({ exp; })) thread_panicf((msg), (thread)); })
#else
static void thread_stkov(struct thread_entry *thread)
{
#if NUM_CORES > 1
    const unsigned int core = thread->core;
#endif
    static char name[32];
    thread_get_name(name, 32, thread);
    panicf("Stkov %s" IF_COP(" (%d)"), name IF_COP(, core));
}
#define THREAD_PANICF(msg, thread)
#define THREAD_ASSERT(exp, msg, thread)
#endif /* THREAD_EXTRA_CHECKS */

static void add_to_list(struct thread_entry **list, struct thread_entry *thread)
{
    if (*list == NULL)
    {
        thread->next = thread;
        thread->prev = thread;
        *list = thread;
    }
    else
    {
        /* Insert last */
        thread->next = *list;
        thread->prev = (*list)->prev;
        thread->prev->next = thread;
        (*list)->prev = thread;
        
        /* Insert next
         thread->next = (*list)->next;
         thread->prev = *list;
         thread->next->prev = thread;
         (*list)->next = thread;
         */
    }
}

static void remove_from_list(struct thread_entry **list,
                      struct thread_entry *thread)
{
    if (list != NULL)
    {
        if (thread == thread->next)
        {
            *list = NULL;
            return;
        }
        
        if (thread == *list)
            *list = thread->next;
    }
    
    /* Fix links to jump over the removed entry. */
    thread->prev->next = thread->next;
    thread->next->prev = thread->prev;
}

static void check_sleepers(void) __attribute__ ((noinline));
static void check_sleepers(void)
{
    const unsigned int core = CURRENT_CORE;
    struct thread_entry *current, *next;
    
    /* Check sleeping threads. */
    current = cores[core].sleeping;
    
    for (;;)
    {
        next = current->next;
        
        if ((unsigned)current_tick >= GET_STATE_ARG(current->statearg))
        {
            /* Sleep timeout has been reached so bring the thread
             * back to life again. */
            remove_from_list(&cores[core].sleeping, current);
            add_to_list(&cores[core].running, current);
            current->statearg = 0;
            
            /* If there is no more processes in the list, break the loop. */
            if (cores[core].sleeping == NULL)
                break;
            
            current = next;
            continue;
        }
        
        current = next;
        
        /* Break the loop once we have walked through the list of all
         * sleeping processes. */
        if (current == cores[core].sleeping)
            break;
    }
}

/* Safely finish waking all threads potentialy woken by interrupts -
 * statearg already zeroed in wakeup_thread. */
static void wake_list_awaken(void) __attribute__ ((noinline));
static void wake_list_awaken(void)
{
    const unsigned int core = CURRENT_CORE;
    int oldlevel = set_irq_level(HIGHEST_IRQ_LEVEL);

    /* No need for another check in the IRQ lock since IRQs are allowed
       only to add threads to the waking list. They won't be adding more
       until we're done here though. */

    struct thread_entry *waking = cores[core].waking;
    struct thread_entry *running = cores[core].running;

    if (running != NULL)
    {
        /* Place waking threads at the end of the running list. */
        struct thread_entry *tmp;
        waking->prev->next  = running;
        running->prev->next = waking;
        tmp                 = running->prev;
        running->prev       = waking->prev;
        waking->prev        = tmp;
    }
    else
    {
        /* Just transfer the list as-is - just came out of a core
         * sleep. */
        cores[core].running = waking;
    }

    /* Done with waking list */
    cores[core].waking = NULL;
    set_irq_level(oldlevel);
}

static inline void sleep_core(void)
{
    const unsigned int core = CURRENT_CORE;

    for (;;)
    {
        /* We want to do these ASAP as it may change the decision to sleep
           the core or the core has woken because an interrupt occurred
           and posted a message to a queue. */
        if (cores[core].waking != NULL)
            wake_list_awaken();

        if (cores[core].last_tick != current_tick)
        {
            if (cores[core].sleeping != NULL)
                check_sleepers();
            cores[core].last_tick = current_tick;
        }
        
        /* We must sleep until there is at least one process in the list
         * of running processes. */
        if (cores[core].running != NULL)
            break;

        /* Enter sleep mode to reduce power usage, woken up on interrupt */
        core_sleep();
    }
}

#ifdef RB_PROFILE
static int get_threadnum(struct thread_entry *thread)
{
    int i;
    
    for (i = 0; i < MAXTHREADS; i++)
    {
        if (&threads[i] == thread)
            return i;
    }
    
    return -1;
}

void profile_thread(void) {
    profstart(get_threadnum(cores[CURRENT_CORE].running));
}
#endif

static void change_thread_state(struct thread_entry **blocked_list) __attribute__ ((noinline));
static void change_thread_state(struct thread_entry **blocked_list)
{
    const unsigned int core = CURRENT_CORE;
    struct thread_entry *old;
    unsigned long new_state;
    
    /* Remove the thread from the list of running threads. */
    old = cores[core].running;
    new_state = GET_STATE(old->statearg);

    /* Check if a thread state change has been requested. */
    if (new_state)
    {
        /* Change running thread state and switch to next thread. */
        remove_from_list(&cores[core].running, old);
        
        /* And put the thread into a new list of inactive threads. */
        if (new_state == STATE_BLOCKED)
            add_to_list(blocked_list, old);
        else
            add_to_list(&cores[core].sleeping, old);
        
#ifdef HAVE_PRIORITY_SCHEDULING
        /* Reset priorities */
        if (old->priority == cores[core].highest_priority)
            cores[core].highest_priority = 100;
#endif
    }
    else
        /* Switch to the next running thread. */
        cores[core].running = old->next;
}

/*---------------------------------------------------------------------------
 * Switch thread in round robin fashion.
 *---------------------------------------------------------------------------
 */
void switch_thread(bool save_context, struct thread_entry **blocked_list)
{
    const unsigned int core = CURRENT_CORE;

#ifdef RB_PROFILE
    profile_thread_stopped(get_threadnum(cores[core].running));
#endif
    unsigned int *stackptr;
    
#ifdef SIMULATOR
    /* Do nothing */
#else

    /* Begin task switching by saving our current context so that we can
     * restore the state of the current thread later to the point prior
     * to this call. */
    if (save_context)
    {
        store_context(&cores[core].running->context);

        /* Check if the current thread stack is overflown */
        stackptr = cores[core].running->stack;
        if(stackptr[0] != DEADBEEF)
            thread_stkov(cores[core].running);
    
        /* Rearrange thread lists as needed */
        change_thread_state(blocked_list);

        /* This has to be done after the scheduler is finished with the
           blocked_list pointer so that an IRQ can't kill us by attempting
           a wake but before attempting any core sleep. */
        if (cores[core].switch_to_irq_level != STAY_IRQ_LEVEL)
        {
            int level = cores[core].switch_to_irq_level;
            cores[core].switch_to_irq_level = STAY_IRQ_LEVEL;
            set_irq_level(level);
        }
    }
    
    /* Go through the list of sleeping task to check if we need to wake up
     * any of them due to timeout. Also puts core into sleep state until
     * there is at least one running process again. */
    sleep_core();
    
#ifdef HAVE_PRIORITY_SCHEDULING
    /* Select the new task based on priorities and the last time a process
     * got CPU time. */
    for (;;)
    {
        int priority = cores[core].running->priority;

        if (priority < cores[core].highest_priority)
            cores[core].highest_priority = priority;

        if (priority == cores[core].highest_priority ||
                (current_tick - cores[core].running->last_run >
                 priority * 8) ||
            cores[core].running->priority_x != 0)
        {
            break;
        }

        cores[core].running = cores[core].running->next;
    }
    
    /* Reset the value of thread's last running time to the current time. */
    cores[core].running->last_run = current_tick;
#endif
    
#endif
    
    /* And finally give control to the next thread. */
    load_context(&cores[core].running->context);
    
#ifdef RB_PROFILE
    profile_thread_started(get_threadnum(cores[core].running));
#endif
}

void sleep_thread(int ticks)
{
    struct thread_entry *current;

    current = cores[CURRENT_CORE].running;

#ifdef HAVE_SCHEDULER_BOOSTCTRL
    if (STATE_IS_BOOSTED(current->statearg))
    {
        boosted_threads--;
        if (!boosted_threads)
        {
            cpu_boost(false);
        }
    }
#endif

    /* Set the thread's new state and timeout and finally force a task switch
     * so that scheduler removes thread from the list of running processes
     * and puts it in list of sleeping tasks. */
    SET_STATE(current->statearg, STATE_SLEEPING, current_tick + ticks + 1);
    
    switch_thread(true, NULL);
}

void block_thread(struct thread_entry **list)
{
    struct thread_entry *current;
    
    /* Get the entry for the current running thread. */
    current = cores[CURRENT_CORE].running;

#ifdef HAVE_SCHEDULER_BOOSTCTRL
    /* Keep the boosted state over indefinite block calls, because
     * we are waiting until the earliest time that someone else
     * completes an action */
    unsigned long boost_flag = STATE_IS_BOOSTED(current->statearg);
#endif

    /* We are not allowed to mix blocking types in one queue. */
    THREAD_ASSERT(*list != NULL && GET_STATE((*list)->statearg) == STATE_BLOCKED_W_TMO,
                  "Blocking violation B->*T", current);
    
    /* Set the state to blocked and ask the scheduler to switch tasks,
     * this takes us off of the run queue until we are explicitly woken */
    SET_STATE(current->statearg, STATE_BLOCKED, 0);

    switch_thread(true, list);

#ifdef HAVE_SCHEDULER_BOOSTCTRL
    /* Reset only the boosted flag to indicate we are up and running again. */
    current->statearg = boost_flag;
#else
    /* Clear all flags to indicate we are up and running again. */
    current->statearg = 0;
#endif
}

void block_thread_w_tmo(struct thread_entry **list, int timeout)
{
    struct thread_entry *current;
    /* Get the entry for the current running thread. */
    current = cores[CURRENT_CORE].running;
    
#ifdef HAVE_SCHEDULER_BOOSTCTRL
    /* A block with a timeout is a sleep situation, whatever we are waiting
     * for _may or may not_ happen, regardless of boost state, (user input
     * for instance), so this thread no longer needs to boost */
    if (STATE_IS_BOOSTED(current->statearg))
    {
        boosted_threads--;
        if (!boosted_threads)
        {
            cpu_boost(false);
        }
    }
#endif

    /* We can store only one thread to the "list" if thread is used
     * in other list (such as core's list for sleeping tasks). */
    THREAD_ASSERT(*list == NULL, "Blocking violation T->*B", current);
    
    /* Set the state to blocked with the specified timeout */
    SET_STATE(current->statearg, STATE_BLOCKED_W_TMO, current_tick + timeout);

    /* Set the "list" for explicit wakeup */
    *list = current;

    /* Now force a task switch and block until we have been woken up
     * by another thread or timeout is reached. */
    switch_thread(true, NULL);

    /* It is now safe for another thread to block on this "list" */
    *list = NULL;
}

#if !defined(SIMULATOR)
void set_irq_level_and_block_thread(struct thread_entry **list, int level)
{
    cores[CURRENT_CORE].switch_to_irq_level = level;
    block_thread(list);
}

void set_irq_level_and_block_thread_w_tmo(struct thread_entry **list,
                                          int timeout, int level)
{
    cores[CURRENT_CORE].switch_to_irq_level = level;
    block_thread_w_tmo(list, timeout);
}
#endif

void wakeup_thread(struct thread_entry **list)
{
    struct thread_entry *thread;
    
    /* Check if there is a blocked thread at all. */
    if (*list == NULL)
    {
        return ;
    }
    
    /* Wake up the last thread first. */
    thread = *list;
    
    /* Determine thread's current state. */
    switch (GET_STATE(thread->statearg)) 
    {
        case STATE_BLOCKED:
            /* Remove thread from the list of blocked threads and add it
             * to the scheduler's list of running processes. List removal
             * is safe since each object maintains it's own list of
             * sleepers and queues protect against reentrancy. */
            remove_from_list(list, thread);
            add_to_list(cores[IF_COP2(thread->core)].wakeup_list, thread);

        case STATE_BLOCKED_W_TMO:
            /* Just remove the timeout to cause scheduler to immediately
             * wake up the thread. */
            thread->statearg = 0;
            break;
        
        default:
            /* Nothing to do. Thread has already been woken up
             * or it's state is not blocked or blocked with timeout. */
            return ;
    }
}

inline static int find_empty_thread_slot(void)
{
    int n;
    
    for (n = 0; n < MAXTHREADS; n++)
    {
        if (threads[n].name == NULL)
            return n;
    }
    
    return -1;
}

/* Like wakeup_thread but safe against IRQ corruption when IRQs are disabled
   before calling. */
void wakeup_thread_irq_safe(struct thread_entry **list)
{
    struct core_entry *core = &cores[CURRENT_CORE];
    /* Switch wakeup lists and call wakeup_thread */
    core->wakeup_list = &core->waking;
    wakeup_thread(list);
    /* Switch back to normal running list */
    core->wakeup_list = &core->running;
}

/*---------------------------------------------------------------------------
 * Create a thread
 * If using a dual core architecture, specify which core to start the thread
 * on, and whether to fall back to the other core if it can't be created
 * Return ID if context area could be allocated, else NULL.
 *---------------------------------------------------------------------------
 */
struct thread_entry* 
    create_thread(void (*function)(void), void* stack, int stack_size,
                  const char *name IF_PRIO(, int priority)
          IF_COP(, unsigned int core, bool fallback))
{
    unsigned int i;
    unsigned int stacklen;
    unsigned int *stackptr;
    int slot;
    struct thread_entry *thread;

/*****
 * Ugly code alert!
 * To prevent ifdef hell while keeping the binary size down, we define
 * core here if it hasn't been passed as a parameter
 *****/
#if NUM_CORES == 1
#define core CPU
#endif

#if NUM_CORES > 1
/* If the kernel hasn't initialised on the COP (most likely due to an old
 * bootloader) then refuse to start threads on the COP
 */
    if ((core == COP) && !cores[core].kernel_running)
    {
        if (fallback)
            return create_thread(function, stack, stack_size, name
                                 IF_PRIO(, priority) IF_COP(, CPU, false));
        else
            return NULL;
    }
#endif

    slot = find_empty_thread_slot();
    if (slot < 0)
    {
        return NULL;
    }
    
    /* Munge the stack to make it easy to spot stack overflows */
    stacklen = stack_size / sizeof(int);
    stackptr = stack;
    for(i = 0;i < stacklen;i++)
    {
        stackptr[i] = DEADBEEF;
    }

    /* Store interesting information */
    thread = &threads[slot];
    thread->name = name;
    thread->stack = stack;
    thread->stack_size = stack_size;
    thread->statearg = 0;
#ifdef HAVE_PRIORITY_SCHEDULING
    thread->priority_x = 0;
    thread->priority = priority;
    cores[core].highest_priority = 100;
#endif

#if NUM_CORES > 1
    thread->core = core;

    /* Writeback stack munging or anything else before starting */
    if (core != CURRENT_CORE)
    {
        flush_icache();
    }
#endif
    
    /* Align stack to an even 32 bit boundary */
    thread->context.sp = (void*)(((unsigned int)stack + stack_size) & ~3);

    /* Load the thread's context structure with needed startup information */
    THREAD_STARTUP_INIT(core, thread, function);

    add_to_list(&cores[core].running, thread);

    return thread;
#if NUM_CORES == 1
#undef core
#endif
}

#ifdef HAVE_SCHEDULER_BOOSTCTRL
void trigger_cpu_boost(void)
{
    if (!STATE_IS_BOOSTED(cores[CURRENT_CORE].running->statearg))
    {
        SET_BOOST_STATE(cores[CURRENT_CORE].running->statearg);
        if (!boosted_threads)
        {
            cpu_boost(true);
        }
        boosted_threads++;
    }
}
#endif

/*---------------------------------------------------------------------------
 * Remove a thread on the current core from the scheduler.
 * Parameter is the ID as returned from create_thread().
 *---------------------------------------------------------------------------
 */
void remove_thread(struct thread_entry *thread)
{
    const unsigned int core = CURRENT_CORE;

    if (thread == NULL)
        thread = cores[core].running;
    
    /* Free the entry by removing thread name. */
    thread->name = NULL;
#ifdef HAVE_PRIORITY_SCHEDULING
    cores[IF_COP2(thread->core)].highest_priority = 100;
#endif
    
    if (thread == cores[IF_COP2(thread->core)].running)
    {
        remove_from_list(&cores[IF_COP2(thread->core)].running, thread);
#if NUM_CORES > 1
        /* Switch to the idle stack if not on the main core (where "main"
         * runs) */
        if (core != CPU)
        {
            switch_to_idle_stack(core);
        }

        flush_icache();
#endif
        switch_thread(false, NULL);
        /* This should never and must never be reached - if it is, the
         * state is corrupted */
        THREAD_PANICF("remove_thread->K:*R", thread);
    }
    
    if (thread == cores[IF_COP2(thread->core)].sleeping)
        remove_from_list(&cores[IF_COP2(thread->core)].sleeping, thread);
    else
        remove_from_list(NULL, thread);
}

#ifdef HAVE_PRIORITY_SCHEDULING
int thread_set_priority(struct thread_entry *thread, int priority)
{
    int old_priority;
    
    if (thread == NULL)
        thread = cores[CURRENT_CORE].running;

    old_priority = thread->priority;
    thread->priority = priority;
    cores[IF_COP2(thread->core)].highest_priority = 100;
    
    return old_priority;
}

int thread_get_priority(struct thread_entry *thread)
{
    if (thread == NULL)
        thread = cores[CURRENT_CORE].running;

    return thread->priority;
}

void priority_yield(void)
{
    struct thread_entry *thread = cores[CURRENT_CORE].running;
    thread->priority_x = 1;
    switch_thread(true, NULL);
    thread->priority_x = 0;
}
#endif /* HAVE_PRIORITY_SCHEDULING */

struct thread_entry * thread_get_current(void)
{
    return cores[CURRENT_CORE].running;
}

void init_threads(void)
{
    const unsigned int core = CURRENT_CORE;
    int slot;

    /* CPU will initialize first and then sleep */
    slot = find_empty_thread_slot();
#if THREAD_EXTRA_CHECKS
    /* This can fail if, for example, .bss isn't zero'ed out by the loader
       or threads is in the wrong section. */
    if (slot < 0) {
        panicf("uninitialized threads[]");
    }
#endif
    
    cores[core].sleeping = NULL;
    cores[core].running = NULL;
    cores[core].waking = NULL;
    cores[core].wakeup_list = &cores[core].running;
#ifdef HAVE_EXTENDED_MESSAGING_AND_NAME
    cores[core].switch_to_irq_level = STAY_IRQ_LEVEL;
#endif
    threads[slot].name = main_thread_name;
    threads[slot].statearg = 0;
    threads[slot].context.start = 0; /* core's main thread already running */
#if NUM_CORES > 1
    threads[slot].core = core;
#endif
#ifdef HAVE_PRIORITY_SCHEDULING
    threads[slot].priority = PRIORITY_USER_INTERFACE;
    threads[slot].priority_x = 0;
    cores[core].highest_priority = 100;
#endif
    add_to_list(&cores[core].running, &threads[slot]);
    
    /* In multiple core setups, each core has a different stack.  There is
     * probably a much better way to do this. */
    if (core == CPU)
    {
#ifdef HAVE_SCHEDULER_BOOSTCTRL
        boosted_threads = 0;
#endif
        threads[slot].stack = stackbegin;
        threads[slot].stack_size = (int)stackend - (int)stackbegin;
#if NUM_CORES > 1  /* This code path will not be run on single core targets */
        /* Mark CPU initialized */
        cores[CPU].kernel_running = true;
        /* Do _not_ wait for the COP to init in the bootloader because it doesn't */
        /* TODO: HAL interface for this */
        /* Wake up coprocessor and let it initialize kernel and threads */
        COP_CTL = PROC_WAKE;
        /* Sleep until finished */
        CPU_CTL = PROC_SLEEP;
    } 
    else 
    {
        /* Initial stack is the COP idle stack */
        threads[slot].stack = cop_idlestackbegin;
        threads[slot].stack_size = IDLE_STACK_SIZE;
        /* Mark COP initialized */
        cores[COP].kernel_running = true;
        /* Get COP safely primed inside switch_thread where it will remain
         * until a thread actually exists on it */
        CPU_CTL = PROC_WAKE;
        set_irq_level(0);
        remove_thread(NULL);
#endif /* NUM_CORES */
    }
}

int thread_stack_usage(const struct thread_entry *thread)
{
    unsigned int i;
    unsigned int *stackptr = thread->stack;

    for (i = 0;i < thread->stack_size/sizeof(int);i++)
    {
        if (stackptr[i] != DEADBEEF)
            break;
    }

    return ((thread->stack_size - i * sizeof(int)) * 100) /
        thread->stack_size;
}

#if NUM_CORES > 1
/*---------------------------------------------------------------------------
 * Returns the maximum percentage of the core's idle stack ever used during
 * runtime.
 *---------------------------------------------------------------------------
 */
int idle_stack_usage(unsigned int core)
{
    unsigned int *stackptr = idle_stacks[core];
    int i, usage = 0;

    for (i = 0; i < IDLE_STACK_WORDS; i++)
    {
        if (stackptr[i] != DEADBEEF)
        {
            usage = ((IDLE_STACK_WORDS - i) * 100) / IDLE_STACK_WORDS;
            break;
        }
    }

    return usage;
}
#endif

int thread_get_status(const struct thread_entry *thread)
{
    return GET_STATE(thread->statearg);
}

/*---------------------------------------------------------------------------
 * Fills in the buffer with the specified thread's name. If the name is NULL,
 * empty, or the thread is in destruct state a formatted ID is written
 * instead.
 *---------------------------------------------------------------------------
 */
void thread_get_name(char *buffer, int size,
                     struct thread_entry *thread)
{
    if (size <= 0)
        return;

    *buffer = '\0';

    if (thread)
    {
        /* Display thread name if one or ID if none */
        const char *name = thread->name;
        const char *fmt = "%s";
        if (name == NULL || *name == '\0')
        {
            name = (const char *)thread;
            fmt = "%08lX";
        }
        snprintf(buffer, size, fmt, name);
    }
}