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rockbox/firmware/kernel/thread.c
Michael Sevakis 3e73866110 Add CPU mode asserts to kernel on blocking functions. 
This scourge finds it's way back in far too often.
Right now, only defined for ARM.

Have fun!

Change-Id: Ib21be09ebf71dec10dc652a7a664779251f49644
2017-01-21 14:25:52 -05:00

1577 lines
50 KiB
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2002 by Ulf Ralberg
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "config.h"
#ifdef HAVE_SIGALTSTACK_THREADS
/*
* The sp check in glibc __longjmp_chk() will cause
* a fatal error when switching threads via longjmp().
*/
#undef _FORTIFY_SOURCE
#endif
#include "thread-internal.h"
#include "kernel.h"
#include "cpu.h"
#include "string.h"
#ifdef RB_PROFILE
#include <profile.h>
#endif
#include "core_alloc.h"
/* Define THREAD_EXTRA_CHECKS as 1 to enable additional state checks */
#ifdef DEBUG
#define THREAD_EXTRA_CHECKS 1 /* Always 1 for DEBUG */
#else
#define THREAD_EXTRA_CHECKS 0
#endif
/****************************************************************************
* ATTENTION!! *
* See notes below on implementing processor-specific portions! *
****************************************************************************
*
* General locking order to guarantee progress. Order must be observed but
* all stages are not nescessarily obligatory. Going from 1) to 3) is
* perfectly legal.
*
* 1) IRQ
* This is first because of the likelyhood of having an interrupt occur that
* also accesses one of the objects farther down the list. Any non-blocking
* synchronization done may already have a lock on something during normal
* execution and if an interrupt handler running on the same processor as
* the one that has the resource locked were to attempt to access the
* resource, the interrupt handler would wait forever waiting for an unlock
* that will never happen. There is no danger if the interrupt occurs on
* a different processor because the one that has the lock will eventually
* unlock and the other processor's handler may proceed at that time. Not
* nescessary when the resource in question is definitely not available to
* interrupt handlers.
*
* 2) Kernel Object
* 1) May be needed beforehand if the kernel object allows dual-use such as
* event queues. The kernel object must have a scheme to protect itself from
* access by another processor and is responsible for serializing the calls
* to block_thread and wakeup_thread both to themselves and to each other.
* Objects' queues are also protected here.
*
* 3) Thread Slot
* This locks access to the thread's slot such that its state cannot be
* altered by another processor when a state change is in progress such as
* when it is in the process of going on a blocked list. An attempt to wake
* a thread while it is still blocking will likely desync its state with
* the other resources used for that state.
*
* 4) Core Lists
* These lists are specific to a particular processor core and are accessible
* by all processor cores and interrupt handlers. The running (rtr) list is
* the prime example where a thread may be added by any means.
*/
/*---------------------------------------------------------------------------
* Processor specific: core_sleep/core_wake/misc. notes
*
* ARM notes:
* FIQ is not dealt with by the scheduler code and is simply restored if it
* must by masked for some reason - because threading modifies a register
* that FIQ may also modify and there's no way to accomplish it atomically.
* s3c2440 is such a case.
*
* Audio interrupts are generally treated at a higher priority than others
* usage of scheduler code with interrupts higher than HIGHEST_IRQ_LEVEL
* are not in general safe. Special cases may be constructed on a per-
* source basis and blocking operations are not available.
*
* core_sleep procedure to implement for any CPU to ensure an asychronous
* wakup never results in requiring a wait until the next tick (up to
* 10000uS!). May require assembly and careful instruction ordering.
*
* 1) On multicore, stay awake if directed to do so by another. If so, goto
* step 4.
* 2) If processor requires, atomically reenable interrupts and perform step
* 3.
* 3) Sleep the CPU core. If wakeup itself enables interrupts (stop #0x2000
* on Coldfire) goto step 5.
* 4) Enable interrupts.
* 5) Exit procedure.
*
* core_wake and multprocessor notes for sleep/wake coordination:
* If possible, to wake up another processor, the forcing of an interrupt on
* the woken core by the waker core is the easiest way to ensure a non-
* delayed wake and immediate execution of any woken threads. If that isn't
* available then some careful non-blocking synchonization is needed (as on
* PP targets at the moment).
*---------------------------------------------------------------------------
*
*
*---------------------------------------------------------------------------
* Priority distribution structure (one category for each possible priority):
*
* +----+----+----+ ... +------+
* hist: | F0 | F1 | F2 | | Fn-1 |
* +----+----+----+ ... +------+
* mask: | b0 | b1 | b2 | | bn-1 |
* +----+----+----+ ... +------+
*
* F = count of threads at priority category n (frequency)
* b = bitmask of non-zero priority categories (occupancy)
*
* / if H[n] != 0 : 1
* b[n] = |
* \ else : 0
*
*---------------------------------------------------------------------------
* Basic priority inheritance priotocol (PIP):
*
* Mn = mutex n, Tn = thread n
*
* A lower priority thread inherits the priority of the highest priority
* thread blocked waiting for it to complete an action (such as release a
* mutex or respond to a message via queue_send):
*
* 1) T2->M1->T1
*
* T1 owns M1, T2 is waiting for M1 to realease M1. If T2 has a higher
* priority than T1 then T1 inherits the priority of T2.
*
* 2) T3
* \/
* T2->M1->T1
*
* Situation is like 1) but T2 and T3 are both queued waiting for M1 and so
* T1 inherits the higher of T2 and T3.
*
* 3) T3->M2->T2->M1->T1
*
* T1 owns M1, T2 owns M2. If T3 has a higher priority than both T1 and T2,
* then T1 inherits the priority of T3 through T2.
*
* Blocking chains can grow arbitrarily complex (though it's best that they
* not form at all very often :) and build-up from these units.
*---------------------------------------------------------------------------
*/
static FORCE_INLINE void core_sleep(IF_COP_VOID(unsigned int core));
static FORCE_INLINE void store_context(void* addr);
static FORCE_INLINE void load_context(const void* addr);
/****************************************************************************
* Processor/OS-specific section - include necessary core support
*/
#include "asm/thread.c"
#if defined (CPU_PP)
#include "thread-pp.c"
#endif /* CPU_PP */
/*
* End Processor-specific section
***************************************************************************/
static NO_INLINE NORETURN_ATTR
void thread_panicf(const char *msg, struct thread_entry *thread)
{
IF_COP( const unsigned int core = thread->core; )
static char name[sizeof (((struct thread_debug_info *)0)->name)];
format_thread_name(name, sizeof (name), thread);
panicf ("%s %s" IF_COP(" (%d)"), msg, name IF_COP(, core));
}
static NO_INLINE void thread_stkov(struct thread_entry *thread)
{
thread_panicf("Stkov", thread);
}
#if THREAD_EXTRA_CHECKS
#define THREAD_PANICF(msg, thread) \
thread_panicf(msg, thread)
#define THREAD_ASSERT(exp, msg, thread) \
({ if (!({ exp; })) thread_panicf((msg), (thread)); })
#else
#define THREAD_PANICF(msg, thread) \
do {} while (1)
#define THREAD_ASSERT(exp, msg, thread) \
do {} while (0)
#endif /* THREAD_EXTRA_CHECKS */
/* Thread locking */
#if NUM_CORES > 1
#define LOCK_THREAD(thread) \
({ corelock_lock(&(thread)->slot_cl); })
#define TRY_LOCK_THREAD(thread) \
({ corelock_try_lock(&(thread)->slot_cl); })
#define UNLOCK_THREAD(thread) \
({ corelock_unlock(&(thread)->slot_cl); })
#else /* NUM_CORES == 1*/
#define LOCK_THREAD(thread) \
({ (void)(thread); })
#define TRY_LOCK_THREAD(thread) \
({ (void)(thread); })
#define UNLOCK_THREAD(thread) \
({ (void)(thread); })
#endif /* NUM_CORES */
/* RTR list */
#define RTR_LOCK(corep) \
corelock_lock(&(corep)->rtr_cl)
#define RTR_UNLOCK(corep) \
corelock_unlock(&(corep)->rtr_cl)
#ifdef HAVE_PRIORITY_SCHEDULING
#define rtr_add_entry(corep, priority) \
prio_add_entry(&(corep)->rtr_dist, (priority))
#define rtr_subtract_entry(corep, priority) \
prio_subtract_entry(&(corep)->rtr_dist, (priority))
#define rtr_move_entry(corep, from, to) \
prio_move_entry(&(corep)->rtr_dist, (from), (to))
#else /* !HAVE_PRIORITY_SCHEDULING */
#define rtr_add_entry(corep, priority) \
do {} while (0)
#define rtr_subtract_entry(corep, priority) \
do {} while (0)
#define rtr_move_entry(corep, from, to) \
do {} while (0)
#endif /* HAVE_PRIORITY_SCHEDULING */
static FORCE_INLINE void thread_store_context(struct thread_entry *thread)
{
store_context(&thread->context);
#if (CONFIG_PLATFORM & PLATFORM_HOSTED)
thread->__errno = errno;
#endif
}
static FORCE_INLINE void thread_load_context(struct thread_entry *thread)
{
#if (CONFIG_PLATFORM & PLATFORM_HOSTED)
errno = thread->__errno;
#endif
load_context(&thread->context);
}
static FORCE_INLINE unsigned int
should_switch_tasks(struct thread_entry *thread)
{
#ifdef HAVE_PRIORITY_SCHEDULING
const unsigned int core = CURRENT_CORE;
#if NUM_CORES > 1
/* Forget about it if different CPU */
if (thread->core != core)
return THREAD_OK;
#endif
/* Just woke something therefore a thread is on the run queue */
struct thread_entry *current =
RTR_THREAD_FIRST(&__core_id_entry(core)->rtr);
if (LIKELY(thread->priority >= current->priority))
return THREAD_OK;
/* There is a thread ready to run of higher priority on the same
* core as the current one; recommend a task switch. */
return THREAD_OK | THREAD_SWITCH;
#else
return THREAD_OK;
(void)thread;
#endif /* HAVE_PRIORITY_SCHEDULING */
}
#ifdef HAVE_PRIORITY_SCHEDULING
/*---------------------------------------------------------------------------
* Increment frequency at category "priority"
*---------------------------------------------------------------------------
*/
static inline unsigned int prio_add_entry(
struct priority_distribution *pd, int priority)
{
unsigned int count = ++pd->hist[priority];
if (count == 1)
priobit_set_bit(&pd->mask, priority);
return count;
}
/*---------------------------------------------------------------------------
* Decrement frequency at category "priority"
*---------------------------------------------------------------------------
*/
static inline unsigned int prio_subtract_entry(
struct priority_distribution *pd, int priority)
{
unsigned int count = --pd->hist[priority];
if (count == 0)
priobit_clear_bit(&pd->mask, priority);
return count;
}
/*---------------------------------------------------------------------------
* Remove from one category and add to another
*---------------------------------------------------------------------------
*/
static inline void prio_move_entry(
struct priority_distribution *pd, int from, int to)
{
if (--pd->hist[from] == 0)
priobit_clear_bit(&pd->mask, from);
if (++pd->hist[to] == 1)
priobit_set_bit(&pd->mask, to);
}
#endif /* HAVE_PRIORITY_SCHEDULING */
/*---------------------------------------------------------------------------
* Common init for new thread basic info
*---------------------------------------------------------------------------
*/
static void new_thread_base_init(struct thread_entry *thread,
void **stackp, size_t *stack_sizep,
const char *name IF_PRIO(, int priority)
IF_COP(, unsigned int core))
{
ALIGN_BUFFER(*stackp, *stack_sizep, MIN_STACK_ALIGN);
thread->stack = *stackp;
thread->stack_size = *stack_sizep;
thread->name = name;
wait_queue_init(&thread->queue);
thread->wqp = NULL;
tmo_set_dequeued(thread);
#ifdef HAVE_PRIORITY_SCHEDULING
thread->skip_count = 0;
thread->blocker = NULL;
thread->base_priority = priority;
thread->priority = priority;
memset(&thread->pdist, 0, sizeof(thread->pdist));
prio_add_entry(&thread->pdist, priority);
#endif
#if NUM_CORES > 1
thread->core = core;
#endif
#ifdef HAVE_SCHEDULER_BOOSTCTRL
thread->cpu_boost = 0;
#endif
}
/*---------------------------------------------------------------------------
* Move a thread onto the core's run queue and promote it
*---------------------------------------------------------------------------
*/
static inline void core_rtr_add(struct core_entry *corep,
struct thread_entry *thread)
{
RTR_LOCK(corep);
rtr_queue_add(&corep->rtr, thread);
rtr_add_entry(corep, thread->priority);
#ifdef HAVE_PRIORITY_SCHEDULING
thread->skip_count = thread->base_priority;
#endif
thread->state = STATE_RUNNING;
RTR_UNLOCK(corep);
}
/*---------------------------------------------------------------------------
* Remove a thread from the core's run queue
*---------------------------------------------------------------------------
*/
static inline void core_rtr_remove(struct core_entry *corep,
struct thread_entry *thread)
{
RTR_LOCK(corep);
rtr_queue_remove(&corep->rtr, thread);
rtr_subtract_entry(corep, thread->priority);
/* Does not demote state */
RTR_UNLOCK(corep);
}
/*---------------------------------------------------------------------------
* Move a thread back to a running state on its core
*---------------------------------------------------------------------------
*/
static NO_INLINE void core_schedule_wakeup(struct thread_entry *thread)
{
const unsigned int core = IF_COP_CORE(thread->core);
struct core_entry *corep = __core_id_entry(core);
core_rtr_add(corep, thread);
#if NUM_CORES > 1
if (core != CURRENT_CORE)
core_wake(core);
#endif
}
#ifdef HAVE_PRIORITY_SCHEDULING
/*---------------------------------------------------------------------------
* Locks the thread registered as the owner of the block and makes sure it
* didn't change in the meantime
*---------------------------------------------------------------------------
*/
#if NUM_CORES == 1
static inline struct thread_entry * lock_blocker_thread(struct blocker *bl)
{
return bl->thread;
}
#else /* NUM_CORES > 1 */
static struct thread_entry * lock_blocker_thread(struct blocker *bl)
{
/* The blocker thread may change during the process of trying to
capture it */
while (1)
{
struct thread_entry *t = bl->thread;
/* TRY, or else deadlocks are possible */
if (!t)
{
struct blocker_splay *blsplay = (struct blocker_splay *)bl;
if (corelock_try_lock(&blsplay->cl))
{
if (!bl->thread)
return NULL; /* Still multi */
corelock_unlock(&blsplay->cl);
}
}
else
{
if (TRY_LOCK_THREAD(t))
{
if (bl->thread == t)
return t;
UNLOCK_THREAD(t);
}
}
}
}
#endif /* NUM_CORES */
static inline void unlock_blocker_thread(struct blocker *bl)
{
#if NUM_CORES > 1
struct thread_entry *blt = bl->thread;
if (blt)
UNLOCK_THREAD(blt);
else
corelock_unlock(&((struct blocker_splay *)bl)->cl);
#endif /* NUM_CORES > 1*/
(void)bl;
}
/*---------------------------------------------------------------------------
* Change the priority and rtr entry for a running thread
*---------------------------------------------------------------------------
*/
static inline void set_rtr_thread_priority(
struct thread_entry *thread, int priority)
{
const unsigned int core = IF_COP_CORE(thread->core);
struct core_entry *corep = __core_id_entry(core);
RTR_LOCK(corep);
rtr_move_entry(corep, thread->priority, priority);
thread->priority = priority;
RTR_UNLOCK(corep);
}
/*---------------------------------------------------------------------------
* Finds the highest priority thread in a list of threads. If the list is
* empty, the PRIORITY_IDLE is returned.
*
* It is possible to use the struct priority_distribution within an object
* instead of scanning the remaining threads in the list but as a compromise,
* the resulting per-object memory overhead is saved at a slight speed
* penalty under high contention.
*---------------------------------------------------------------------------
*/
static int wait_queue_find_priority(struct __wait_queue *wqp)
{
int highest_priority = PRIORITY_IDLE;
struct thread_entry *thread = WQ_THREAD_FIRST(wqp);
while (thread != NULL)
{
int priority = thread->priority;
if (priority < highest_priority)
highest_priority = priority;
thread = WQ_THREAD_NEXT(thread);
}
return highest_priority;
}
/*---------------------------------------------------------------------------
* Register priority with blocking system and bubble it down the chain if
* any until we reach the end or something is already equal or higher.
*
* NOTE: A simultaneous circular wait could spin deadlock on multiprocessor
* targets but that same action also guarantees a circular block anyway and
* those are prevented, right? :-)
*---------------------------------------------------------------------------
*/
static void inherit_priority(
struct blocker * const blocker0, struct blocker *bl,
struct thread_entry *blt, int newblpr)
{
int oldblpr = bl->priority;
while (1)
{
if (blt == NULL)
{
/* Multiple owners */
struct blocker_splay *blsplay = (struct blocker_splay *)bl;
/* Recurse down the all the branches of this; it's the only way.
We might meet the same queue several times if more than one of
these threads is waiting the same queue. That isn't a problem
for us since we early-terminate, just notable. */
FOR_EACH_BITARRAY_SET_BIT(&blsplay->mask, slotnum)
{
bl->priority = oldblpr; /* To see the change each time */
blt = __thread_slot_entry(slotnum);
LOCK_THREAD(blt);
inherit_priority(blocker0, bl, blt, newblpr);
}
corelock_unlock(&blsplay->cl);
return;
}
bl->priority = newblpr;
/* Update blocker thread inheritance record */
if (newblpr < PRIORITY_IDLE)
prio_add_entry(&blt->pdist, newblpr);
if (oldblpr < PRIORITY_IDLE)
prio_subtract_entry(&blt->pdist, oldblpr);
int oldpr = blt->priority;
int newpr = priobit_ffs(&blt->pdist.mask);
if (newpr == oldpr)
break; /* No blocker thread priority change */
if (blt->state == STATE_RUNNING)
{
set_rtr_thread_priority(blt, newpr);
break; /* Running: last in chain */
}
/* Blocker is blocked */
blt->priority = newpr;
bl = blt->blocker;
if (LIKELY(bl == NULL))
break; /* Block doesn't support PIP */
if (UNLIKELY(bl == blocker0))
break; /* Full circle - deadlock! */
/* Blocker becomes current thread and the process repeats */
struct __wait_queue *wqp = wait_queue_ptr(blt);
struct thread_entry *t = blt;
blt = lock_blocker_thread(bl);
UNLOCK_THREAD(t);
/* Adjust this wait queue */
oldblpr = bl->priority;
if (newpr <= oldblpr)
newblpr = newpr;
else if (oldpr <= oldblpr)
newblpr = wait_queue_find_priority(wqp);
if (newblpr == oldblpr)
break; /* Queue priority not changing */
}
UNLOCK_THREAD(blt);
}
/*---------------------------------------------------------------------------
* Quick-inherit of priority elevation. 'thread' must be not runnable
*---------------------------------------------------------------------------
*/
static void priority_inherit_internal_inner(struct thread_entry *thread,
int blpr)
{
if (prio_add_entry(&thread->pdist, blpr) == 1 && blpr < thread->priority)
thread->priority = blpr;
}
static inline void priority_inherit_internal(struct thread_entry *thread,
int blpr)
{
if (blpr < PRIORITY_IDLE)
priority_inherit_internal_inner(thread, blpr);
}
/*---------------------------------------------------------------------------
* Quick-disinherit of priority elevation. 'thread' must current
*---------------------------------------------------------------------------
*/
static void priority_disinherit_internal_inner(struct thread_entry *thread,
int blpr)
{
if (prio_subtract_entry(&thread->pdist, blpr) == 0 &&
blpr <= thread->priority)
{
int priority = priobit_ffs(&thread->pdist.mask);
if (priority != thread->priority)
set_rtr_thread_priority(thread, priority);
}
}
static inline void priority_disinherit_internal(struct thread_entry *thread,
int blpr)
{
if (blpr < PRIORITY_IDLE)
priority_disinherit_internal_inner(thread, blpr);
}
void priority_disinherit(struct thread_entry *thread, struct blocker *bl)
{
LOCK_THREAD(thread);
priority_disinherit_internal(thread, bl->priority);
UNLOCK_THREAD(thread);
}
/*---------------------------------------------------------------------------
* Transfer ownership from a single owner to a multi-owner splay from a wait
* queue
*---------------------------------------------------------------------------
*/
static void wakeup_thread_queue_multi_transfer(struct thread_entry *thread)
{
/* All threads will have the same blocker and queue; only we are changing
it now */
struct __wait_queue *wqp = wait_queue_ptr(thread);
struct blocker *bl = thread->blocker;
struct blocker_splay *blsplay = (struct blocker_splay *)bl;
struct thread_entry *blt = bl->thread;
/* The first thread is already locked and is assumed tagged "multi" */
int count = 1;
/* Multiple versions of the wait queue may be seen if doing more than
one thread; queue removal isn't destructive to the pointers of the node
being removed; this may lead to the blocker priority being wrong for a
time but it gets fixed up below after getting exclusive access to the
queue */
while (1)
{
thread->blocker = NULL;
wait_queue_remove(thread);
unsigned int slotnum = THREAD_ID_SLOT(thread->id);
threadbit_set_bit(&blsplay->mask, slotnum);
struct thread_entry *tnext = WQ_THREAD_NEXT(thread);
if (tnext == NULL || tnext->retval == 0)
break;
UNLOCK_THREAD(thread);
count++;
thread = tnext;
LOCK_THREAD(thread);
}
/* Locking order reverses here since the threads are no longer on the
queued side */
if (count > 1)
corelock_lock(&blsplay->cl);
LOCK_THREAD(blt);
int blpr = bl->priority;
priority_disinherit_internal(blt, blpr);
if (count > 1)
{
blsplay->blocker.thread = NULL;
blpr = wait_queue_find_priority(wqp);
FOR_EACH_BITARRAY_SET_BIT(&blsplay->mask, slotnum)
{
UNLOCK_THREAD(thread);
thread = __thread_slot_entry(slotnum);
LOCK_THREAD(thread);
priority_inherit_internal(thread, blpr);
core_schedule_wakeup(thread);
}
}
else
{
/* Becomes a simple, direct transfer */
blsplay->blocker.thread = thread;
if (thread->priority <= blpr)
blpr = wait_queue_find_priority(wqp);
priority_inherit_internal(thread, blpr);
core_schedule_wakeup(thread);
}
UNLOCK_THREAD(thread);
bl->priority = blpr;
UNLOCK_THREAD(blt);
if (count > 1)
corelock_unlock(&blsplay->cl);
blt->retval = count;
}
/*---------------------------------------------------------------------------
* Transfer ownership to a thread waiting for an objects and transfer
* inherited priority boost from other waiters. This algorithm knows that
* blocking chains may only unblock from the very end.
*
* Only the owning thread itself may call this and so the assumption that
* it is the running thread is made.
*---------------------------------------------------------------------------
*/
static void wakeup_thread_transfer(struct thread_entry *thread)
{
/* Waking thread inherits priority boost from object owner (blt) */
struct blocker *bl = thread->blocker;
struct thread_entry *blt = bl->thread;
THREAD_ASSERT(__running_self_entry() == blt,
"UPPT->wrong thread", __running_self_entry());
LOCK_THREAD(blt);
thread->blocker = NULL;
struct __wait_queue *wqp = wait_queue_remove(thread);
int blpr = bl->priority;
/* Remove the object's boost from the owning thread */
priority_disinherit_internal_inner(blt, blpr);
struct thread_entry *tnext = WQ_THREAD_FIRST(wqp);
if (LIKELY(tnext == NULL))
{
/* Expected shortcut - no more waiters */
blpr = PRIORITY_IDLE;
}
else
{
/* If thread is at the blocker priority, its removal may drop it */
if (thread->priority <= blpr)
blpr = wait_queue_find_priority(wqp);
priority_inherit_internal_inner(thread, blpr);
}
bl->thread = thread; /* This thread pwns */
core_schedule_wakeup(thread);
UNLOCK_THREAD(thread);
bl->priority = blpr; /* Save highest blocked priority */
UNLOCK_THREAD(blt);
}
/*---------------------------------------------------------------------------
* Readjust priorities when waking a thread blocked waiting for another
* in essence "releasing" the thread's effect on the object owner. Can be
* performed from any context.
*---------------------------------------------------------------------------
*/
static void wakeup_thread_release(struct thread_entry *thread)
{
struct blocker *bl = thread->blocker;
struct thread_entry *blt = lock_blocker_thread(bl);
thread->blocker = NULL;
struct __wait_queue *wqp = wait_queue_remove(thread);
/* Off to see the wizard... */
core_schedule_wakeup(thread);
if (thread->priority > bl->priority)
{
/* Queue priority won't change */
UNLOCK_THREAD(thread);
unlock_blocker_thread(bl);
return;
}
UNLOCK_THREAD(thread);
int newblpr = wait_queue_find_priority(wqp);
if (newblpr == bl->priority)
{
/* Blocker priority won't change */
unlock_blocker_thread(bl);
return;
}
inherit_priority(bl, bl, blt, newblpr);
}
#endif /* HAVE_PRIORITY_SCHEDULING */
/*---------------------------------------------------------------------------
* Explicitly wakeup a thread on a blocking queue. Only effects threads of
* STATE_BLOCKED and STATE_BLOCKED_W_TMO.
*
* INTERNAL: Intended for use by kernel and not programs.
*---------------------------------------------------------------------------
*/
unsigned int wakeup_thread_(struct thread_entry *thread
IF_PRIO(, enum wakeup_thread_protocol proto))
{
LOCK_THREAD(thread);
/* Determine thread's current state. */
switch (thread->state)
{
case STATE_BLOCKED:
case STATE_BLOCKED_W_TMO:
#ifdef HAVE_PRIORITY_SCHEDULING
/* Threads with PIP blockers cannot specify "WAKEUP_DEFAULT" */
if (thread->blocker != NULL)
{
static void (* const funcs[])(struct thread_entry *thread)
ICONST_ATTR =
{
[WAKEUP_DEFAULT] = NULL,
[WAKEUP_TRANSFER] = wakeup_thread_transfer,
[WAKEUP_RELEASE] = wakeup_thread_release,
[WAKEUP_TRANSFER_MULTI] = wakeup_thread_queue_multi_transfer,
};
/* Call the specified unblocking PIP (does the rest) */
funcs[proto](thread);
}
else
#endif /* HAVE_PRIORITY_SCHEDULING */
{
wait_queue_remove(thread);
core_schedule_wakeup(thread);
UNLOCK_THREAD(thread);
}
return should_switch_tasks(thread);
case STATE_RUNNING:
if (wait_queue_try_remove(thread))
{
UNLOCK_THREAD(thread);
return THREAD_OK; /* timed out */
}
default:
UNLOCK_THREAD(thread);
return THREAD_NONE;
}
}
/*---------------------------------------------------------------------------
* Check the core's timeout list when at least one thread is due to wake.
* Filtering for the condition is done before making the call. Resets the
* tick when the next check will occur.
*---------------------------------------------------------------------------
*/
static NO_INLINE void check_tmo_expired_inner(struct core_entry *corep)
{
const long tick = current_tick; /* snapshot the current tick */
long next_tmo_check = tick + 60*HZ; /* minimum duration: once/minute */
struct thread_entry *prev = NULL;
struct thread_entry *thread = TMO_THREAD_FIRST(&corep->tmo);
/* If there are no processes waiting for a timeout, just keep the check
tick from falling into the past. */
/* Break the loop once we have walked through the list of all
* sleeping processes or have removed them all. */
while (thread != NULL)
{
/* Check sleeping threads. Allow interrupts between checks. */
enable_irq();
struct thread_entry *next = TMO_THREAD_NEXT(thread);
/* Lock thread slot against explicit wakeup */
disable_irq();
LOCK_THREAD(thread);
unsigned int state = thread->state;
if (LIKELY(state >= TIMEOUT_STATE_FIRST &&
TIME_BEFORE(tick, thread->tmo_tick)))
{
/* Timeout still pending - this will be the usual case */
if (TIME_BEFORE(thread->tmo_tick, next_tmo_check))
{
/* Move the next check up to its time */
next_tmo_check = thread->tmo_tick;
}
prev = thread;
}
else
{
/* TODO: there are no priority-inheriting timeout blocks
right now but the procedure should be established */
/* Sleep timeout has been reached / garbage collect stale list
items */
tmo_queue_expire(&corep->tmo, prev, thread);
if (state >= TIMEOUT_STATE_FIRST)
core_rtr_add(corep, thread);
/* removed this one - prev doesn't change */
}
UNLOCK_THREAD(thread);
thread = next;
}
corep->next_tmo_check = next_tmo_check;
}
static FORCE_INLINE void check_tmo_expired(struct core_entry *corep)
{
if (!TIME_BEFORE(current_tick, corep->next_tmo_check))
check_tmo_expired_inner(corep);
}
/*---------------------------------------------------------------------------
* Prepares a the current thread to sleep forever or for the given duration.
*---------------------------------------------------------------------------
*/
static FORCE_INLINE void prepare_block(struct thread_entry *current,
unsigned int state, int timeout)
{
const unsigned int core = IF_COP_CORE(current->core);
/* Remove the thread from the list of running threads. */
struct core_entry *corep = __core_id_entry(core);
core_rtr_remove(corep, current);
if (timeout >= 0)
{
/* Sleep may expire. */
long tmo_tick = current_tick + timeout;
current->tmo_tick = tmo_tick;
if (TIME_BEFORE(tmo_tick, corep->next_tmo_check))
corep->next_tmo_check = tmo_tick;
tmo_queue_register(&corep->tmo, current);
if (state == STATE_BLOCKED)
state = STATE_BLOCKED_W_TMO;
}
/* Report new state. */
current->state = state;
}
/*---------------------------------------------------------------------------
* Switch thread in round robin fashion for any given priority. Any thread
* that removed itself from the running list first must specify itself in
* the paramter.
*
* INTERNAL: Intended for use by kernel and not programs.
*---------------------------------------------------------------------------
*/
void switch_thread(void)
{
const unsigned int core = CURRENT_CORE;
struct core_entry *corep = __core_id_entry(core);
struct thread_entry *thread = corep->running;
if (thread)
{
#ifdef RB_PROFILE
profile_thread_stopped(THREAD_ID_SLOT(thread->id));
#endif
#ifdef DEBUG
/* Check core_ctx buflib integrity */
core_check_valid();
#endif
thread_store_context(thread);
/* Check if the current thread stack is overflown */
if (UNLIKELY(thread->stack[0] != DEADBEEF) && thread->stack_size > 0)
thread_stkov(thread);
}
/* TODO: make a real idle task */
for (;;)
{
disable_irq();
/* Check for expired timeouts */
check_tmo_expired(corep);
RTR_LOCK(corep);
if (!RTR_EMPTY(&corep->rtr))
break;
thread = NULL;
/* Enter sleep mode to reduce power usage */
RTR_UNLOCK(corep);
core_sleep(IF_COP(core));
/* Awakened by interrupt or other CPU */
}
thread = (thread && thread->state == STATE_RUNNING) ?
RTR_THREAD_NEXT(thread) : RTR_THREAD_FIRST(&corep->rtr);
#ifdef HAVE_PRIORITY_SCHEDULING
/* Select the new task based on priorities and the last time a
* process got CPU time relative to the highest priority runnable
* task. If priority is not a feature, then FCFS is used (above). */
int max = priobit_ffs(&corep->rtr_dist.mask);
for (;;)
{
int priority = thread->priority;
int diff;
/* This ridiculously simple method of aging seems to work
* suspiciously well. It does tend to reward CPU hogs (under
* yielding) but that's generally not desirable at all. On
* the plus side, it, relatively to other threads, penalizes
* excess yielding which is good if some high priority thread
* is performing no useful work such as polling for a device
* to be ready. Of course, aging is only employed when higher
* and lower priority threads are runnable. The highest
* priority runnable thread(s) are never skipped unless a
* lower-priority process has aged sufficiently. Priorities
* of REALTIME class are run strictly according to priority
* thus are not subject to switchout due to lower-priority
* processes aging; they must give up the processor by going
* off the run list. */
if (LIKELY(priority <= max) ||
(priority > PRIORITY_REALTIME &&
(diff = priority - max, ++thread->skip_count > diff*diff)))
{
break;
}
thread = RTR_THREAD_NEXT(thread);
}
thread->skip_count = 0; /* Reset aging counter */
#endif /* HAVE_PRIORITY_SCHEDULING */
rtr_queue_make_first(&corep->rtr, thread);
corep->running = thread;
RTR_UNLOCK(corep);
enable_irq();
#ifdef RB_PROFILE
profile_thread_started(THREAD_ID_SLOT(thread->id));
#endif
/* And finally, give control to the next thread. */
thread_load_context(thread);
}
/*---------------------------------------------------------------------------
* Sleeps a thread for at least a specified number of ticks with zero being
* a wait until the next tick.
*
* INTERNAL: Intended for use by kernel and not programs.
*---------------------------------------------------------------------------
*/
void sleep_thread(int ticks)
{
struct thread_entry *current = __running_self_entry();
LOCK_THREAD(current);
prepare_block(current, STATE_SLEEPING, MAX(ticks, 0) + 1);
UNLOCK_THREAD(current);
}
/*---------------------------------------------------------------------------
* Block a thread on a blocking queue for explicit wakeup. If timeout is
* negative, the block is infinite.
*
* INTERNAL: Intended for use by kernel and not programs.
*---------------------------------------------------------------------------
*/
void block_thread_(struct thread_entry *current, int timeout)
{
LOCK_THREAD(current);
#ifdef HAVE_PRIORITY_SCHEDULING
struct blocker *bl = current->blocker;
struct thread_entry *blt = NULL;
if (bl != NULL)
{
current->blocker = bl;
blt = lock_blocker_thread(bl);
}
#endif /* HAVE_PRIORITY_SCHEDULING */
wait_queue_register(current);
prepare_block(current, STATE_BLOCKED, timeout);
#ifdef HAVE_PRIORITY_SCHEDULING
if (bl != NULL)
{
int newblpr = current->priority;
UNLOCK_THREAD(current);
if (newblpr < bl->priority)
inherit_priority(bl, bl, blt, newblpr);
else
unlock_blocker_thread(bl); /* Queue priority won't change */
}
else
#endif /* HAVE_PRIORITY_SCHEDULING */
{
UNLOCK_THREAD(current);
}
}
/*---------------------------------------------------------------------------
* Place the current core in idle mode - woken up on interrupt or wake
* request from another core.
*---------------------------------------------------------------------------
*/
void core_idle(void)
{
disable_irq();
core_sleep(IF_COP(CURRENT_CORE));
}
/*---------------------------------------------------------------------------
* Create a thread. If using a dual core architecture, specify which core to
* start the thread on.
*
* Return ID if context area could be allocated, else NULL.
*---------------------------------------------------------------------------
*/
unsigned int create_thread(void (*function)(void),
void* stack, size_t stack_size,
unsigned flags, const char *name
IF_PRIO(, int priority)
IF_COP(, unsigned int core))
{
struct thread_entry *thread = thread_alloc();
if (thread == NULL)
return 0;
new_thread_base_init(thread, &stack, &stack_size, name
IF_PRIO(, priority) IF_COP(, core));
unsigned int stack_words = stack_size / sizeof (uintptr_t);
if (stack_words == 0)
return 0;
/* Munge the stack to make it easy to spot stack overflows */
for (unsigned int i = 0; i < stack_words; i++)
((uintptr_t *)stack)[i] = DEADBEEF;
#if NUM_CORES > 1
/* Writeback stack munging or anything else before starting */
if (core != CURRENT_CORE)
commit_dcache();
#endif
thread->context.sp = (typeof (thread->context.sp))(stack + stack_size);
THREAD_STARTUP_INIT(core, thread, function);
int oldlevel = disable_irq_save();
LOCK_THREAD(thread);
thread->state = STATE_FROZEN;
if (!(flags & CREATE_THREAD_FROZEN))
core_schedule_wakeup(thread);
unsigned int id = thread->id; /* Snapshot while locked */
UNLOCK_THREAD(thread);
restore_irq(oldlevel);
return id;
}
/*---------------------------------------------------------------------------
* Block the current thread until another thread terminates. A thread may
* wait on itself to terminate but that will deadlock
*.
* Parameter is the ID as returned from create_thread().
*---------------------------------------------------------------------------
*/
void thread_wait(unsigned int thread_id)
{
ASSERT_CPU_MODE(CPU_MODE_THREAD_CONTEXT);
struct thread_entry *current = __running_self_entry();
struct thread_entry *thread = __thread_id_entry(thread_id);
corelock_lock(&thread->waiter_cl);
if (thread->id == thread_id && thread->state != STATE_KILLED)
{
disable_irq();
block_thread(current, TIMEOUT_BLOCK, &thread->queue, NULL);
corelock_unlock(&thread->waiter_cl);
switch_thread();
return;
}
corelock_unlock(&thread->waiter_cl);
}
/*---------------------------------------------------------------------------
* Exit the current thread
*---------------------------------------------------------------------------
*/
static USED_ATTR NORETURN_ATTR
void thread_exit_final(struct thread_entry *current)
{
/* Slot is no longer this thread */
new_thread_id(current);
current->name = NULL;
/* No longer using resources from creator */
wait_queue_wake(&current->queue);
UNLOCK_THREAD(current);
corelock_unlock(&current->waiter_cl);
thread_free(current);
switch_thread();
/* This should never and must never be reached - if it is, the
* state is corrupted */
THREAD_PANICF("thread_exit->K:*R", current);
}
void thread_exit(void)
{
struct core_entry *corep = __core_id_entry(CURRENT_CORE);
register struct thread_entry *current = corep->running;
/* Cancel CPU boost if any */
cancel_cpu_boost();
disable_irq();
corelock_lock(&current->waiter_cl);
LOCK_THREAD(current);
#ifdef HAVE_PRIORITY_SCHEDULING
/* Only one bit in the mask should be set with a frequency on 1 which
* represents the thread's own base priority otherwise threads are waiting
* on an abandoned object */
if (priobit_popcount(&current->pdist.mask) != 1 ||
current->pdist.hist[priobit_ffs(&current->pdist.mask)] > 1)
thread_panicf("abandon ship!", current);
#endif /* HAVE_PRIORITY_SCHEDULING */
/* Remove from scheduler lists */
tmo_queue_remove(&corep->tmo, current);
prepare_block(current, STATE_KILLED, -1);
corep->running = NULL; /* No switch_thread context save */
#ifdef RB_PROFILE
profile_thread_stopped(THREAD_ID_SLOT(current->id));
#endif
/* Do final release of resources and remove the thread */
#if NUM_CORES > 1
thread_exit_finalize(current->core, current);
#else
thread_exit_final(current);
#endif
}
#ifdef HAVE_PRIORITY_SCHEDULING
/*---------------------------------------------------------------------------
* Sets the thread's relative base priority for the core it runs on. Any
* needed inheritance changes also may happen.
*---------------------------------------------------------------------------
*/
int thread_set_priority(unsigned int thread_id, int priority)
{
if (priority < HIGHEST_PRIORITY || priority > LOWEST_PRIORITY)
return -1; /* Invalid priority argument */
int old_base_priority = -1;
struct thread_entry *thread = __thread_id_entry(thread_id);
const int oldlevel = disable_irq_save();
LOCK_THREAD(thread);
if (thread->id != thread_id || thread->state == STATE_KILLED)
goto done; /* Invalid thread */
old_base_priority = thread->base_priority;
if (priority == old_base_priority)
goto done; /* No base priority change */
thread->base_priority = priority;
/* Adjust the thread's priority influence on itself */
prio_move_entry(&thread->pdist, old_base_priority, priority);
int old_priority = thread->priority;
int new_priority = priobit_ffs(&thread->pdist.mask);
if (old_priority == new_priority)
goto done; /* No running priority change */
if (thread->state == STATE_RUNNING)
{
/* This thread is running - just change location on the run queue.
Also sets thread->priority. */
set_rtr_thread_priority(thread, new_priority);
goto done;
}
/* Thread is blocked */
struct blocker *bl = thread->blocker;
if (bl == NULL)
{
thread->priority = new_priority;
goto done; /* End of transitive blocks */
}
struct thread_entry *blt = lock_blocker_thread(bl);
struct __wait_queue *wqp = wait_queue_ptr(thread);
thread->priority = new_priority;
UNLOCK_THREAD(thread);
thread = NULL;
int oldblpr = bl->priority;
int newblpr = oldblpr;
if (new_priority < oldblpr)
newblpr = new_priority;
else if (old_priority <= oldblpr)
newblpr = wait_queue_find_priority(wqp);
if (newblpr == oldblpr)
{
unlock_blocker_thread(bl);
goto done;
}
inherit_priority(bl, bl, blt, newblpr);
done:
if (thread)
UNLOCK_THREAD(thread);
restore_irq(oldlevel);
return old_base_priority;
}
/*---------------------------------------------------------------------------
* Returns the current base priority for a thread.
*---------------------------------------------------------------------------
*/
int thread_get_priority(unsigned int thread_id)
{
struct thread_entry *thread = __thread_id_entry(thread_id);
int base_priority = thread->base_priority;
/* Simply check without locking slot. It may or may not be valid by the
* time the function returns anyway. If all tests pass, it is the
* correct value for when it was valid. */
if (thread->id != thread_id || thread->state == STATE_KILLED)
base_priority = -1;
return base_priority;
}
#endif /* HAVE_PRIORITY_SCHEDULING */
/*---------------------------------------------------------------------------
* Starts a frozen thread - similar semantics to wakeup_thread except that
* the thread is on no scheduler or wakeup queue at all. It exists simply by
* virtue of the slot having a state of STATE_FROZEN.
*---------------------------------------------------------------------------
*/
void thread_thaw(unsigned int thread_id)
{
struct thread_entry *thread = __thread_id_entry(thread_id);
int oldlevel = disable_irq_save();
LOCK_THREAD(thread);
/* If thread is the current one, it cannot be frozen, therefore
* there is no need to check that. */
if (thread->id == thread_id && thread->state == STATE_FROZEN)
core_schedule_wakeup(thread);
UNLOCK_THREAD(thread);
restore_irq(oldlevel);
}
#if NUM_CORES > 1
/*---------------------------------------------------------------------------
* Switch the processor that the currently executing thread runs on.
*---------------------------------------------------------------------------
*/
static USED_ATTR NORETURN_ATTR
void switch_core_final(unsigned int old_core, struct thread_entry *current)
{
/* Old core won't be using slot resources at this point */
core_schedule_wakeup(current);
UNLOCK_THREAD(current);
#ifdef RB_PROFILE
profile_thread_stopped(THREAD_ID_SLOT(current->id));
#endif
switch_thread();
/* not reached */
THREAD_PANICF("switch_core_final->same core!", current);
(void)old_core;
}
unsigned int switch_core(unsigned int new_core)
{
const unsigned int old_core = CURRENT_CORE;
if (old_core == new_core)
return old_core; /* No change */
struct core_entry *corep = __core_id_entry(old_core);
struct thread_entry *current = corep->running;
disable_irq();
LOCK_THREAD(current);
/* Remove us from old core lists */
tmo_queue_remove(&corep->tmo, current);
core_rtr_remove(corep, current);
corep->running = NULL; /* No switch_thread context save */
/* Do the actual migration */
current->core = new_core;
switch_thread_core(old_core, current);
/* Executing on new core */
return old_core;
}
#endif /* NUM_CORES > 1 */
#ifdef HAVE_SCHEDULER_BOOSTCTRL
/*---------------------------------------------------------------------------
* Change the boost state of a thread boosting or unboosting the CPU
* as required.
*---------------------------------------------------------------------------
*/
static inline void boost_thread(struct thread_entry *thread, bool boost)
{
if ((thread->cpu_boost != 0) != boost)
{
thread->cpu_boost = boost;
cpu_boost(boost);
}
}
void trigger_cpu_boost(void)
{
boost_thread(__running_self_entry(), true);
}
void cancel_cpu_boost(void)
{
boost_thread(__running_self_entry(), false);
}
#endif /* HAVE_SCHEDULER_BOOSTCTRL */
/*---------------------------------------------------------------------------
* Initialize threading API. This assumes interrupts are not yet enabled. On
* multicore setups, no core is allowed to proceed until create_thread calls
* are safe to perform.
*---------------------------------------------------------------------------
*/
void INIT_ATTR init_threads(void)
{
const unsigned int core = CURRENT_CORE;
if (core == CPU)
{
thread_alloc_init(); /* before using cores! */
/* Create main thread */
struct thread_entry *thread = thread_alloc();
if (thread == NULL)
{
/* WTF? There really must be a slot available at this stage.
* This can fail if, for example, .bss isn't zero'ed out by the
* loader or threads is in the wrong section. */
THREAD_PANICF("init_threads->no slot", NULL);
}
size_t stack_size;
void *stack = __get_main_stack(&stack_size);
new_thread_base_init(thread, &stack, &stack_size, __main_thread_name
IF_PRIO(, PRIORITY_MAIN_THREAD) IF_COP(, core));
struct core_entry *corep = __core_id_entry(core);
core_rtr_add(corep, thread);
corep->running = thread;
#ifdef INIT_MAIN_THREAD
init_main_thread(&thread->context);
#endif
}
#if NUM_CORES > 1
/* Boot CPU:
* Wait for other processors to finish their inits since create_thread
* isn't safe to call until the kernel inits are done. The first
* threads created in the system must of course be created by CPU.
* Another possible approach is to initialize all cores and slots
* for each core by CPU, let the remainder proceed in parallel and
* signal CPU when all are finished.
*
* Other:
* After last processor completes, it should signal all others to
* proceed or may signal the next and call thread_exit(). The last one
* to finish will signal CPU.
*/
core_thread_init(core);
if (core != CPU)
{
/* No main thread on coprocessors - go idle and wait */
switch_thread();
THREAD_PANICF("init_threads() - coprocessor returned", NULL);
}
#endif /* NUM_CORES */
}
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