/*************************************************************************** * __________ __ ___. * 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" #include #include #include "thread.h" #include "panic.h" #include "system.h" #include "kernel.h" #include "cpu.h" #include "string.h" #ifdef RB_PROFILE #include #endif /**************************************************************************** * ATTENTION!! * * See notes below on implementing processor-specific portions! * ***************************************************************************/ /* 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 /** * 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(_w_tmo) 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). *--------------------------------------------------------------------------- */ /* Cast to the the machine pointer size, whose size could be < 4 or > 32 * (someday :). */ #define DEADBEEF ((uintptr_t)0xdeadbeefdeadbeefull) static struct core_entry cores[NUM_CORES] IBSS_ATTR; struct thread_entry threads[MAXTHREADS] IBSS_ATTR; static const char main_thread_name[] = "main"; extern uintptr_t stackbegin[]; extern uintptr_t stackend[]; static inline void core_sleep(IF_COP_VOID(unsigned int core)) __attribute__((always_inline)); void check_tmo_threads(void) __attribute__((noinline)); static inline void block_thread_on_l(struct thread_entry *thread, unsigned state) __attribute__((always_inline)); static void add_to_list_tmo(struct thread_entry *thread) __attribute__((noinline)); static void core_schedule_wakeup(struct thread_entry *thread) __attribute__((noinline)); #if NUM_CORES > 1 static inline void run_blocking_ops( unsigned int core, struct thread_entry *thread) __attribute__((always_inline)); #endif static void thread_stkov(struct thread_entry *thread) __attribute__((noinline)); static inline void store_context(void* addr) __attribute__((always_inline)); static inline void load_context(const void* addr) __attribute__((always_inline)); void switch_thread(void) __attribute__((noinline)); /**************************************************************************** * Processor-specific section - include necessary core support */ #if defined(CPU_ARM) #include "thread-arm.c" #if defined (CPU_PP) #include "thread-pp.c" #endif /* CPU_PP */ #elif defined(CPU_COLDFIRE) #include "thread-coldfire.c" #elif CONFIG_CPU == SH7034 #include "thread-sh.c" #elif defined(CPU_MIPS) && CPU_MIPS == 32 #include "thread-mips32.c" #else /* Wouldn't compile anyway */ #error Processor not implemented. #endif /* CONFIG_CPU == */ #ifndef IF_NO_SKIP_YIELD #define IF_NO_SKIP_YIELD(...) #endif /* * End Processor-specific section ***************************************************************************/ #if THREAD_EXTRA_CHECKS static void thread_panicf(const char *msg, struct thread_entry *thread) { IF_COP( const unsigned int core = thread->core; ) 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_COP( const unsigned int core = thread->core; ) 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 */ /* 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); }) #define UNLOCK_THREAD_AT_TASK_SWITCH(thread) \ ({ unsigned int _core = (thread)->core; \ cores[_core].blk_ops.flags |= TBOP_UNLOCK_CORELOCK; \ cores[_core].blk_ops.cl_p = &(thread)->slot_cl; }) #else #define LOCK_THREAD(thread) \ ({ }) #define TRY_LOCK_THREAD(thread) \ ({ }) #define UNLOCK_THREAD(thread) \ ({ }) #define UNLOCK_THREAD_AT_TASK_SWITCH(thread) \ ({ }) #endif /* RTR list */ #define RTR_LOCK(core) \ ({ corelock_lock(&cores[core].rtr_cl); }) #define RTR_UNLOCK(core) \ ({ corelock_unlock(&cores[core].rtr_cl); }) #ifdef HAVE_PRIORITY_SCHEDULING #define rtr_add_entry(core, priority) \ prio_add_entry(&cores[core].rtr, (priority)) #define rtr_subtract_entry(core, priority) \ prio_subtract_entry(&cores[core].rtr, (priority)) #define rtr_move_entry(core, from, to) \ prio_move_entry(&cores[core].rtr, (from), (to)) #else #define rtr_add_entry(core, priority) #define rtr_add_entry_inl(core, priority) #define rtr_subtract_entry(core, priority) #define rtr_subtract_entry_inl(core, priotity) #define rtr_move_entry(core, from, to) #define rtr_move_entry_inl(core, from, to) #endif /*--------------------------------------------------------------------------- * Thread list structure - circular: * +------------------------------+ * | | * +--+---+<-+---+<-+---+<-+---+<-+ * Head->| T | | T | | T | | T | * +->+---+->+---+->+---+->+---+--+ * | | * +------------------------------+ *--------------------------------------------------------------------------- */ /*--------------------------------------------------------------------------- * Adds a thread to a list of threads using "insert last". Uses the "l" * links. *--------------------------------------------------------------------------- */ static void add_to_list_l(struct thread_entry **list, struct thread_entry *thread) { struct thread_entry *l = *list; if (l == NULL) { /* Insert into unoccupied list */ thread->l.prev = thread; thread->l.next = thread; *list = thread; return; } /* Insert last */ thread->l.prev = l->l.prev; thread->l.next = l; l->l.prev->l.next = thread; l->l.prev = thread; } /*--------------------------------------------------------------------------- * Removes a thread from a list of threads. Uses the "l" links. *--------------------------------------------------------------------------- */ static void remove_from_list_l(struct thread_entry **list, struct thread_entry *thread) { struct thread_entry *prev, *next; next = thread->l.next; if (thread == next) { /* The only item */ *list = NULL; return; } if (thread == *list) { /* List becomes next item */ *list = next; } prev = thread->l.prev; /* Fix links to jump over the removed entry. */ next->l.prev = prev; prev->l.next = next; } /*--------------------------------------------------------------------------- * Timeout list structure - circular reverse (to make "remove item" O(1)), * NULL-terminated forward (to ease the far more common forward traversal): * +------------------------------+ * | | * +--+---+<-+---+<-+---+<-+---+<-+ * Head->| T | | T | | T | | T | * +---+->+---+->+---+->+---+-X *--------------------------------------------------------------------------- */ /*--------------------------------------------------------------------------- * Add a thread from the core's timout list by linking the pointers in its * tmo structure. *--------------------------------------------------------------------------- */ static void add_to_list_tmo(struct thread_entry *thread) { struct thread_entry *tmo = cores[IF_COP_CORE(thread->core)].timeout; THREAD_ASSERT(thread->tmo.prev == NULL, "add_to_list_tmo->already listed", thread); thread->tmo.next = NULL; if (tmo == NULL) { /* Insert into unoccupied list */ thread->tmo.prev = thread; cores[IF_COP_CORE(thread->core)].timeout = thread; return; } /* Insert Last */ thread->tmo.prev = tmo->tmo.prev; tmo->tmo.prev->tmo.next = thread; tmo->tmo.prev = thread; } /*--------------------------------------------------------------------------- * Remove a thread from the core's timout list by unlinking the pointers in * its tmo structure. Sets thread->tmo.prev to NULL to indicate the timeout * is cancelled. *--------------------------------------------------------------------------- */ static void remove_from_list_tmo(struct thread_entry *thread) { struct thread_entry **list = &cores[IF_COP_CORE(thread->core)].timeout; struct thread_entry *prev = thread->tmo.prev; struct thread_entry *next = thread->tmo.next; THREAD_ASSERT(prev != NULL, "remove_from_list_tmo->not listed", thread); if (next != NULL) next->tmo.prev = prev; if (thread == *list) { /* List becomes next item and empty if next == NULL */ *list = next; /* Mark as unlisted */ thread->tmo.prev = NULL; } else { if (next == NULL) (*list)->tmo.prev = prev; prev->tmo.next = next; /* Mark as unlisted */ thread->tmo.prev = NULL; } } #ifdef HAVE_PRIORITY_SCHEDULING /*--------------------------------------------------------------------------- * Priority distribution structure (one category for each possible priority): * * +----+----+----+ ... +-----+ * hist: | F0 | F1 | F2 | | F31 | * +----+----+----+ ... +-----+ * mask: | b0 | b1 | b2 | | b31 | * +----+----+----+ ... +-----+ * * 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. *--------------------------------------------------------------------------- */ /*--------------------------------------------------------------------------- * Increment frequency at category "priority" *--------------------------------------------------------------------------- */ static inline unsigned int prio_add_entry( struct priority_distribution *pd, int priority) { unsigned int count; /* Enough size/instruction count difference for ARM makes it worth it to * use different code (192 bytes for ARM). Only thing better is ASM. */ #ifdef CPU_ARM count = pd->hist[priority]; if (++count == 1) pd->mask |= 1 << priority; pd->hist[priority] = count; #else /* This one's better for Coldfire */ if ((count = ++pd->hist[priority]) == 1) pd->mask |= 1 << priority; #endif return count; } /*--------------------------------------------------------------------------- * Decrement frequency at category "priority" *--------------------------------------------------------------------------- */ static inline unsigned int prio_subtract_entry( struct priority_distribution *pd, int priority) { unsigned int count; #ifdef CPU_ARM count = pd->hist[priority]; if (--count == 0) pd->mask &= ~(1 << priority); pd->hist[priority] = count; #else if ((count = --pd->hist[priority]) == 0) pd->mask &= ~(1 << priority); #endif return count; } /*--------------------------------------------------------------------------- * Remove from one category and add to another *--------------------------------------------------------------------------- */ static inline void prio_move_entry( struct priority_distribution *pd, int from, int to) { uint32_t mask = pd->mask; #ifdef CPU_ARM unsigned int count; count = pd->hist[from]; if (--count == 0) mask &= ~(1 << from); pd->hist[from] = count; count = pd->hist[to]; if (++count == 1) mask |= 1 << to; pd->hist[to] = count; #else if (--pd->hist[from] == 0) mask &= ~(1 << from); if (++pd->hist[to] == 1) mask |= 1 << to; #endif pd->mask = mask; } /*--------------------------------------------------------------------------- * Change the priority and rtr entry for a running thread *--------------------------------------------------------------------------- */ static inline void set_running_thread_priority( struct thread_entry *thread, int priority) { const unsigned int core = IF_COP_CORE(thread->core); RTR_LOCK(core); rtr_move_entry(core, thread->priority, priority); thread->priority = priority; RTR_UNLOCK(core); } /*--------------------------------------------------------------------------- * 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 find_highest_priority_in_list_l( struct thread_entry * const thread) { if (LIKELY(thread != NULL)) { /* Go though list until the ending up at the initial thread */ int highest_priority = thread->priority; struct thread_entry *curr = thread; do { int priority = curr->priority; if (priority < highest_priority) highest_priority = priority; curr = curr->l.next; } while (curr != thread); return highest_priority; } return PRIORITY_IDLE; } /*--------------------------------------------------------------------------- * 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 struct thread_entry * blocker_inherit_priority(struct thread_entry *current) { const int priority = current->priority; struct blocker *bl = current->blocker; struct thread_entry * const tstart = current; struct thread_entry *bl_t = bl->thread; /* Blocker cannot change since the object protection is held */ LOCK_THREAD(bl_t); for (;;) { struct thread_entry *next; int bl_pr = bl->priority; if (priority >= bl_pr) break; /* Object priority already high enough */ bl->priority = priority; /* Add this one */ prio_add_entry(&bl_t->pdist, priority); if (bl_pr < PRIORITY_IDLE) { /* Not first waiter - subtract old one */ prio_subtract_entry(&bl_t->pdist, bl_pr); } if (priority >= bl_t->priority) break; /* Thread priority high enough */ if (bl_t->state == STATE_RUNNING) { /* Blocking thread is a running thread therefore there are no * further blockers. Change the "run queue" on which it * resides. */ set_running_thread_priority(bl_t, priority); break; } bl_t->priority = priority; /* If blocking thread has a blocker, apply transitive inheritance */ bl = bl_t->blocker; if (bl == NULL) break; /* End of chain or object doesn't support inheritance */ next = bl->thread; if (UNLIKELY(next == tstart)) break; /* Full-circle - deadlock! */ UNLOCK_THREAD(current); #if NUM_CORES > 1 for (;;) { LOCK_THREAD(next); /* Blocker could change - retest condition */ if (LIKELY(bl->thread == next)) break; UNLOCK_THREAD(next); next = bl->thread; } #endif current = bl_t; bl_t = next; } UNLOCK_THREAD(bl_t); return current; } /*--------------------------------------------------------------------------- * 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. *--------------------------------------------------------------------------- */ struct thread_entry * wakeup_priority_protocol_release(struct thread_entry *thread) { const int priority = thread->priority; struct blocker *bl = thread->blocker; struct thread_entry * const tstart = thread; struct thread_entry *bl_t = bl->thread; /* Blocker cannot change since object will be locked */ LOCK_THREAD(bl_t); thread->blocker = NULL; /* Thread not blocked */ for (;;) { struct thread_entry *next; int bl_pr = bl->priority; if (priority > bl_pr) break; /* Object priority higher */ next = *thread->bqp; if (next == NULL) { /* No more threads in queue */ prio_subtract_entry(&bl_t->pdist, bl_pr); bl->priority = PRIORITY_IDLE; } else { /* Check list for highest remaining priority */ int queue_pr = find_highest_priority_in_list_l(next); if (queue_pr == bl_pr) break; /* Object priority not changing */ /* Change queue priority */ prio_move_entry(&bl_t->pdist, bl_pr, queue_pr); bl->priority = queue_pr; } if (bl_pr > bl_t->priority) break; /* thread priority is higher */ bl_pr = find_first_set_bit(bl_t->pdist.mask); if (bl_pr == bl_t->priority) break; /* Thread priority not changing */ if (bl_t->state == STATE_RUNNING) { /* No further blockers */ set_running_thread_priority(bl_t, bl_pr); break; } bl_t->priority = bl_pr; /* If blocking thread has a blocker, apply transitive inheritance */ bl = bl_t->blocker; if (bl == NULL) break; /* End of chain or object doesn't support inheritance */ next = bl->thread; if (UNLIKELY(next == tstart)) break; /* Full-circle - deadlock! */ UNLOCK_THREAD(thread); #if NUM_CORES > 1 for (;;) { LOCK_THREAD(next); /* Blocker could change - retest condition */ if (LIKELY(bl->thread == next)) break; UNLOCK_THREAD(next); next = bl->thread; } #endif thread = bl_t; bl_t = next; } UNLOCK_THREAD(bl_t); #if NUM_CORES > 1 if (UNLIKELY(thread != tstart)) { /* Relock original if it changed */ LOCK_THREAD(tstart); } #endif return cores[CURRENT_CORE].running; } /*--------------------------------------------------------------------------- * 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. *--------------------------------------------------------------------------- */ struct thread_entry * wakeup_priority_protocol_transfer(struct thread_entry *thread) { /* Waking thread inherits priority boost from object owner */ struct blocker *bl = thread->blocker; struct thread_entry *bl_t = bl->thread; struct thread_entry *next; int bl_pr; THREAD_ASSERT(cores[CURRENT_CORE].running == bl_t, "UPPT->wrong thread", cores[CURRENT_CORE].running); LOCK_THREAD(bl_t); bl_pr = bl->priority; /* Remove the object's boost from the owning thread */ if (prio_subtract_entry(&bl_t->pdist, bl_pr) == 0 && bl_pr <= bl_t->priority) { /* No more threads at this priority are waiting and the old level is * at least the thread level */ int priority = find_first_set_bit(bl_t->pdist.mask); if (priority != bl_t->priority) { /* Adjust this thread's priority */ set_running_thread_priority(bl_t, priority); } } next = *thread->bqp; if (LIKELY(next == NULL)) { /* Expected shortcut - no more waiters */ bl_pr = PRIORITY_IDLE; } else { if (thread->priority <= bl_pr) { /* Need to scan threads remaining in queue */ bl_pr = find_highest_priority_in_list_l(next); } if (prio_add_entry(&thread->pdist, bl_pr) == 1 && bl_pr < thread->priority) { /* Thread priority must be raised */ thread->priority = bl_pr; } } bl->thread = thread; /* This thread pwns */ bl->priority = bl_pr; /* Save highest blocked priority */ thread->blocker = NULL; /* Thread not blocked */ UNLOCK_THREAD(bl_t); return bl_t; } /*--------------------------------------------------------------------------- * No threads must be blocked waiting for this thread except for it to exit. * The alternative is more elaborate cleanup and object registration code. * Check this for risk of silent data corruption when objects with * inheritable blocking are abandoned by the owner - not precise but may * catch something. *--------------------------------------------------------------------------- */ static void check_for_obj_waiters(const char *function, struct thread_entry *thread) { /* Only one bit in the mask should be set with a frequency on 1 which * represents the thread's own base priority */ uint32_t mask = thread->pdist.mask; if ((mask & (mask - 1)) != 0 || thread->pdist.hist[find_first_set_bit(mask)] > 1) { unsigned char name[32]; thread_get_name(name, 32, thread); panicf("%s->%s with obj. waiters", function, name); } } #endif /* HAVE_PRIORITY_SCHEDULING */ /*--------------------------------------------------------------------------- * Move a thread back to a running state on its core. *--------------------------------------------------------------------------- */ static void core_schedule_wakeup(struct thread_entry *thread) { const unsigned int core = IF_COP_CORE(thread->core); RTR_LOCK(core); thread->state = STATE_RUNNING; add_to_list_l(&cores[core].running, thread); rtr_add_entry(core, thread->priority); RTR_UNLOCK(core); #if NUM_CORES > 1 if (core != CURRENT_CORE) core_wake(core); #endif } /*--------------------------------------------------------------------------- * 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. *--------------------------------------------------------------------------- */ void check_tmo_threads(void) { const unsigned int core = CURRENT_CORE; const long tick = current_tick; /* snapshot the current tick */ long next_tmo_check = tick + 60*HZ; /* minimum duration: once/minute */ struct thread_entry *next = cores[core].timeout; /* 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 (next != NULL) { /* Check sleeping threads. Allow interrupts between checks. */ enable_irq(); struct thread_entry *curr = next; next = curr->tmo.next; /* Lock thread slot against explicit wakeup */ disable_irq(); LOCK_THREAD(curr); unsigned state = curr->state; if (state < TIMEOUT_STATE_FIRST) { /* Cleanup threads no longer on a timeout but still on the * list. */ remove_from_list_tmo(curr); } else if (LIKELY(TIME_BEFORE(tick, curr->tmo_tick))) { /* Timeout still pending - this will be the usual case */ if (TIME_BEFORE(curr->tmo_tick, next_tmo_check)) { /* Earliest timeout found so far - move the next check up to its time */ next_tmo_check = curr->tmo_tick; } } else { /* Sleep timeout has been reached so bring the thread back to * life again. */ if (state == STATE_BLOCKED_W_TMO) { #if NUM_CORES > 1 /* Lock the waiting thread's kernel object */ struct corelock *ocl = curr->obj_cl; if (UNLIKELY(corelock_try_lock(ocl) == 0)) { /* Need to retry in the correct order though the need is * unlikely */ UNLOCK_THREAD(curr); corelock_lock(ocl); LOCK_THREAD(curr); if (UNLIKELY(curr->state != STATE_BLOCKED_W_TMO)) { /* Thread was woken or removed explicitely while slot * was unlocked */ corelock_unlock(ocl); remove_from_list_tmo(curr); UNLOCK_THREAD(curr); continue; } } #endif /* NUM_CORES */ remove_from_list_l(curr->bqp, curr); #ifdef HAVE_WAKEUP_EXT_CB if (curr->wakeup_ext_cb != NULL) curr->wakeup_ext_cb(curr); #endif #ifdef HAVE_PRIORITY_SCHEDULING if (curr->blocker != NULL) wakeup_priority_protocol_release(curr); #endif corelock_unlock(ocl); } /* else state == STATE_SLEEPING */ remove_from_list_tmo(curr); RTR_LOCK(core); curr->state = STATE_RUNNING; add_to_list_l(&cores[core].running, curr); rtr_add_entry(core, curr->priority); RTR_UNLOCK(core); } UNLOCK_THREAD(curr); } cores[core].next_tmo_check = next_tmo_check; } /*--------------------------------------------------------------------------- * Performs operations that must be done before blocking a thread but after * the state is saved. *--------------------------------------------------------------------------- */ #if NUM_CORES > 1 static inline void run_blocking_ops( unsigned int core, struct thread_entry *thread) { struct thread_blk_ops *ops = &cores[core].blk_ops; const unsigned flags = ops->flags; if (LIKELY(flags == TBOP_CLEAR)) return; switch (flags) { case TBOP_SWITCH_CORE: core_switch_blk_op(core, thread); /* Fall-through */ case TBOP_UNLOCK_CORELOCK: corelock_unlock(ops->cl_p); break; } ops->flags = TBOP_CLEAR; } #endif /* NUM_CORES > 1 */ #ifdef RB_PROFILE void profile_thread(void) { profstart(cores[CURRENT_CORE].running - threads); } #endif /*--------------------------------------------------------------------------- * Prepares a thread to block on an object's list and/or for a specified * duration - expects object and slot to be appropriately locked if needed * and interrupts to be masked. *--------------------------------------------------------------------------- */ static inline void block_thread_on_l(struct thread_entry *thread, unsigned state) { /* If inlined, unreachable branches will be pruned with no size penalty because state is passed as a constant parameter. */ const unsigned int core = IF_COP_CORE(thread->core); /* Remove the thread from the list of running threads. */ RTR_LOCK(core); remove_from_list_l(&cores[core].running, thread); rtr_subtract_entry(core, thread->priority); RTR_UNLOCK(core); /* Add a timeout to the block if not infinite */ switch (state) { case STATE_BLOCKED: case STATE_BLOCKED_W_TMO: /* Put the thread into a new list of inactive threads. */ add_to_list_l(thread->bqp, thread); if (state == STATE_BLOCKED) break; /* Fall-through */ case STATE_SLEEPING: /* If this thread times out sooner than any other thread, update next_tmo_check to its timeout */ if (TIME_BEFORE(thread->tmo_tick, cores[core].next_tmo_check)) { cores[core].next_tmo_check = thread->tmo_tick; } if (thread->tmo.prev == NULL) { add_to_list_tmo(thread); } /* else thread was never removed from list - just keep it there */ break; } /* Remember the the next thread about to block. */ cores[core].block_task = thread; /* Report new state. */ thread->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 for programs. *--------------------------------------------------------------------------- */ void switch_thread(void) { const unsigned int core = CURRENT_CORE; struct thread_entry *block = cores[core].block_task; struct thread_entry *thread = cores[core].running; /* Get context to save - next thread to run is unknown until all wakeups * are evaluated */ if (block != NULL) { cores[core].block_task = NULL; #if NUM_CORES > 1 if (UNLIKELY(thread == block)) { /* This was the last thread running and another core woke us before * reaching here. Force next thread selection to give tmo threads or * other threads woken before this block a first chance. */ block = NULL; } else #endif { /* Blocking task is the old one */ thread = block; } } #ifdef RB_PROFILE profile_thread_stopped(thread->id & THREAD_ID_SLOT_MASK); #endif /* 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. */ store_context(&thread->context); /* Check if the current thread stack is overflown */ if (UNLIKELY(thread->stack[0] != DEADBEEF)) thread_stkov(thread); #if NUM_CORES > 1 /* Run any blocking operations requested before switching/sleeping */ run_blocking_ops(core, thread); #endif #ifdef HAVE_PRIORITY_SCHEDULING IF_NO_SKIP_YIELD( if (thread->skip_count != -1) ) /* Reset the value of thread's skip count */ thread->skip_count = 0; #endif for (;;) { /* If there are threads on a timeout and the earliest wakeup is due, * check the list and wake any threads that need to start running * again. */ if (!TIME_BEFORE(current_tick, cores[core].next_tmo_check)) { check_tmo_threads(); } disable_irq(); RTR_LOCK(core); thread = cores[core].running; if (UNLIKELY(thread == NULL)) { /* Enter sleep mode to reduce power usage - woken up on interrupt * or wakeup request from another core - expected to enable * interrupts. */ RTR_UNLOCK(core); core_sleep(IF_COP(core)); } else { #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. */ struct priority_distribution *pd = &cores[core].rtr; int max = find_first_set_bit(pd->mask); if (block == NULL) { /* Not switching on a block, tentatively select next thread */ thread = thread->l.next; } 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) || IF_NO_SKIP_YIELD( thread->skip_count == -1 || ) (priority > PRIORITY_REALTIME && (diff = priority - max, ++thread->skip_count > diff*diff))) { cores[core].running = thread; break; } thread = thread->l.next; } #else /* Without priority use a simple FCFS algorithm */ if (block == NULL) { /* Not switching on a block, select next thread */ thread = thread->l.next; cores[core].running = thread; } #endif /* HAVE_PRIORITY_SCHEDULING */ RTR_UNLOCK(core); enable_irq(); break; } } /* And finally give control to the next thread. */ load_context(&thread->context); #ifdef RB_PROFILE profile_thread_started(thread->id & THREAD_ID_SLOT_MASK); #endif } /*--------------------------------------------------------------------------- * 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 for programs. *--------------------------------------------------------------------------- */ void sleep_thread(int ticks) { struct thread_entry *current = cores[CURRENT_CORE].running; LOCK_THREAD(current); /* Set our timeout, remove from run list and join timeout list. */ current->tmo_tick = current_tick + ticks + 1; block_thread_on_l(current, STATE_SLEEPING); UNLOCK_THREAD(current); } /*--------------------------------------------------------------------------- * Indefinitely block a thread on a blocking queue for explicit wakeup. * * INTERNAL: Intended for use by kernel objects and not for programs. *--------------------------------------------------------------------------- */ void block_thread(struct thread_entry *current) { /* Set the state to blocked and take us off of the run queue until we * are explicitly woken */ LOCK_THREAD(current); /* Set the list for explicit wakeup */ block_thread_on_l(current, STATE_BLOCKED); #ifdef HAVE_PRIORITY_SCHEDULING if (current->blocker != NULL) { /* Object supports PIP */ current = blocker_inherit_priority(current); } #endif UNLOCK_THREAD(current); } /*--------------------------------------------------------------------------- * Block a thread on a blocking queue for a specified time interval or until * explicitly woken - whichever happens first. * * INTERNAL: Intended for use by kernel objects and not for programs. *--------------------------------------------------------------------------- */ void block_thread_w_tmo(struct thread_entry *current, int timeout) { /* Get the entry for the current running thread. */ LOCK_THREAD(current); /* Set the state to blocked with the specified timeout */ current->tmo_tick = current_tick + timeout; /* Set the list for explicit wakeup */ block_thread_on_l(current, STATE_BLOCKED_W_TMO); #ifdef HAVE_PRIORITY_SCHEDULING if (current->blocker != NULL) { /* Object supports PIP */ current = blocker_inherit_priority(current); } #endif UNLOCK_THREAD(current); } /*--------------------------------------------------------------------------- * Explicitly wakeup a thread on a blocking queue. Only effects threads of * STATE_BLOCKED and STATE_BLOCKED_W_TMO. * * This code should be considered a critical section by the caller meaning * that the object's corelock should be held. * * INTERNAL: Intended for use by kernel objects and not for programs. *--------------------------------------------------------------------------- */ unsigned int wakeup_thread(struct thread_entry **list) { struct thread_entry *thread = *list; unsigned int result = THREAD_NONE; /* Check if there is a blocked thread at all. */ if (thread == NULL) return result; LOCK_THREAD(thread); /* Determine thread's current state. */ switch (thread->state) { case STATE_BLOCKED: case STATE_BLOCKED_W_TMO: remove_from_list_l(list, thread); result = THREAD_OK; #ifdef HAVE_PRIORITY_SCHEDULING struct thread_entry *current; struct blocker *bl = thread->blocker; if (bl == NULL) { /* No inheritance - just boost the thread by aging */ IF_NO_SKIP_YIELD( if (thread->skip_count != -1) ) thread->skip_count = thread->priority; current = cores[CURRENT_CORE].running; } else { /* Call the specified unblocking PIP */ current = bl->wakeup_protocol(thread); } if (current != NULL && find_first_set_bit(cores[IF_COP_CORE(current->core)].rtr.mask) < current->priority) { /* There is a thread ready to run of higher or same priority on * the same core as the current one; recommend a task switch. * Knowing if this is an interrupt call would be helpful here. */ result |= THREAD_SWITCH; } #endif /* HAVE_PRIORITY_SCHEDULING */ core_schedule_wakeup(thread); break; /* Nothing to do. State is not blocked. */ #if THREAD_EXTRA_CHECKS default: THREAD_PANICF("wakeup_thread->block invalid", thread); case STATE_RUNNING: case STATE_KILLED: break; #endif } UNLOCK_THREAD(thread); return result; } /*--------------------------------------------------------------------------- * Wakeup an entire queue of threads - returns bitwise-or of return bitmask * from each operation or THREAD_NONE of nothing was awakened. Object owning * the queue must be locked first. * * INTERNAL: Intended for use by kernel objects and not for programs. *--------------------------------------------------------------------------- */ unsigned int thread_queue_wake(struct thread_entry **list) { unsigned result = THREAD_NONE; for (;;) { unsigned int rc = wakeup_thread(list); if (rc == THREAD_NONE) break; /* No more threads */ result |= rc; } return result; } /*--------------------------------------------------------------------------- * Assign the thread slot a new ID. Version is 1-255. *--------------------------------------------------------------------------- */ static void new_thread_id(unsigned int slot_num, struct thread_entry *thread) { unsigned int version = (thread->id + (1u << THREAD_ID_VERSION_SHIFT)) & THREAD_ID_VERSION_MASK; /* If wrapped to 0, make it 1 */ if (version == 0) version = 1u << THREAD_ID_VERSION_SHIFT; thread->id = version | (slot_num & THREAD_ID_SLOT_MASK); } /*--------------------------------------------------------------------------- * Find an empty thread slot or MAXTHREADS if none found. The slot returned * will be locked on multicore. *--------------------------------------------------------------------------- */ static struct thread_entry * find_empty_thread_slot(void) { /* Any slot could be on an interrupt-accessible list */ IF_COP( int oldlevel = disable_irq_save(); ) struct thread_entry *thread = NULL; int n; for (n = 0; n < MAXTHREADS; n++) { /* Obtain current slot state - lock it on multicore */ struct thread_entry *t = &threads[n]; LOCK_THREAD(t); if (t->state == STATE_KILLED IF_COP( && t->name != THREAD_DESTRUCT )) { /* Slot is empty - leave it locked and caller will unlock */ thread = t; break; } /* Finished examining slot - no longer busy - unlock on multicore */ UNLOCK_THREAD(t); } IF_COP( restore_irq(oldlevel); ) /* Reenable interrups - this slot is not accesible to them yet */ return thread; } /*--------------------------------------------------------------------------- * Return the thread_entry pointer for a thread_id. Return the current * thread if the ID is 0 (alias for current). *--------------------------------------------------------------------------- */ struct thread_entry * thread_id_entry(unsigned int thread_id) { return (thread_id == THREAD_ID_CURRENT) ? cores[CURRENT_CORE].running : &threads[thread_id & THREAD_ID_SLOT_MASK]; } /*--------------------------------------------------------------------------- * Place the current core in idle mode - woken up on interrupt or wake * request from another core. *--------------------------------------------------------------------------- */ void core_idle(void) { IF_COP( const unsigned int core = CURRENT_CORE; ) disable_irq(); core_sleep(IF_COP(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)) { unsigned int i; unsigned int stack_words; uintptr_t stackptr, stackend; struct thread_entry *thread; unsigned state; int oldlevel; thread = find_empty_thread_slot(); if (thread == NULL) { return 0; } oldlevel = disable_irq_save(); /* Munge the stack to make it easy to spot stack overflows */ stackptr = ALIGN_UP((uintptr_t)stack, sizeof (uintptr_t)); stackend = ALIGN_DOWN((uintptr_t)stack + stack_size, sizeof (uintptr_t)); stack_size = stackend - stackptr; stack_words = stack_size / sizeof (uintptr_t); for (i = 0; i < stack_words; i++) { ((uintptr_t *)stackptr)[i] = DEADBEEF; } /* Store interesting information */ thread->name = name; thread->stack = (uintptr_t *)stackptr; thread->stack_size = stack_size; thread->queue = NULL; #ifdef HAVE_WAKEUP_EXT_CB thread->wakeup_ext_cb = NULL; #endif #ifdef HAVE_SCHEDULER_BOOSTCTRL thread->cpu_boost = 0; #endif #ifdef HAVE_PRIORITY_SCHEDULING memset(&thread->pdist, 0, sizeof(thread->pdist)); thread->blocker = NULL; thread->base_priority = priority; thread->priority = priority; thread->skip_count = priority; prio_add_entry(&thread->pdist, priority); #endif #ifdef HAVE_IO_PRIORITY /* Default to high (foreground) priority */ thread->io_priority = IO_PRIORITY_IMMEDIATE; #endif #if NUM_CORES > 1 thread->core = core; /* Writeback stack munging or anything else before starting */ if (core != CURRENT_CORE) { cpucache_flush(); } #endif /* Thread is not on any timeout list but be a bit paranoid */ thread->tmo.prev = NULL; state = (flags & CREATE_THREAD_FROZEN) ? STATE_FROZEN : STATE_RUNNING; thread->context.sp = (typeof (thread->context.sp))stackend; /* Load the thread's context structure with needed startup information */ THREAD_STARTUP_INIT(core, thread, function); thread->state = state; i = thread->id; /* Snapshot while locked */ if (state == STATE_RUNNING) core_schedule_wakeup(thread); UNLOCK_THREAD(thread); restore_irq(oldlevel); return i; } #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) { struct thread_entry *current = cores[CURRENT_CORE].running; boost_thread(current, true); } void cancel_cpu_boost(void) { struct thread_entry *current = cores[CURRENT_CORE].running; boost_thread(current, false); } #endif /* HAVE_SCHEDULER_BOOSTCTRL */ /*--------------------------------------------------------------------------- * Block the current thread until another thread terminates. A thread may * wait on itself to terminate which prevents it from running again and it * will need to be killed externally. * Parameter is the ID as returned from create_thread(). *--------------------------------------------------------------------------- */ void thread_wait(unsigned int thread_id) { struct thread_entry *current = cores[CURRENT_CORE].running; struct thread_entry *thread = thread_id_entry(thread_id); /* Lock thread-as-waitable-object lock */ corelock_lock(&thread->waiter_cl); /* Be sure it hasn't been killed yet */ if (thread_id == THREAD_ID_CURRENT || (thread->id == thread_id && thread->state != STATE_KILLED)) { IF_COP( current->obj_cl = &thread->waiter_cl; ) current->bqp = &thread->queue; disable_irq(); block_thread(current); corelock_unlock(&thread->waiter_cl); switch_thread(); return; } corelock_unlock(&thread->waiter_cl); } /*--------------------------------------------------------------------------- * Exit the current thread. The Right Way to Do Things (TM). *--------------------------------------------------------------------------- */ void thread_exit(void) { const unsigned int core = CURRENT_CORE; struct thread_entry *current = cores[core].running; /* Cancel CPU boost if any */ cancel_cpu_boost(); disable_irq(); corelock_lock(¤t->waiter_cl); LOCK_THREAD(current); #if defined (ALLOW_REMOVE_THREAD) && NUM_CORES > 1 if (current->name == THREAD_DESTRUCT) { /* Thread being killed - become a waiter */ unsigned int id = current->id; UNLOCK_THREAD(current); corelock_unlock(¤t->waiter_cl); thread_wait(id); THREAD_PANICF("thread_exit->WK:*R", current); } #endif #ifdef HAVE_PRIORITY_SCHEDULING check_for_obj_waiters("thread_exit", current); #endif if (current->tmo.prev != NULL) { /* Cancel pending timeout list removal */ remove_from_list_tmo(current); } /* Switch tasks and never return */ block_thread_on_l(current, STATE_KILLED); #if NUM_CORES > 1 /* Switch to the idle stack if not on the main core (where "main" * runs) - we can hope gcc doesn't need the old stack beyond this * point. */ if (core != CPU) { switch_to_idle_stack(core); } cpucache_flush(); /* At this point, this thread isn't using resources allocated for * execution except the slot itself. */ #endif /* Update ID for this slot */ new_thread_id(current->id, current); current->name = NULL; /* Signal this thread */ thread_queue_wake(¤t->queue); corelock_unlock(¤t->waiter_cl); /* Slot must be unusable until thread is really gone */ UNLOCK_THREAD_AT_TASK_SWITCH(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); } #ifdef ALLOW_REMOVE_THREAD /*--------------------------------------------------------------------------- * Remove a thread from the scheduler. Not The Right Way to Do Things in * normal programs. * * Parameter is the ID as returned from create_thread(). * * Use with care on threads that are not under careful control as this may * leave various objects in an undefined state. *--------------------------------------------------------------------------- */ void remove_thread(unsigned int thread_id) { #if NUM_CORES > 1 /* core is not constant here because of core switching */ unsigned int core = CURRENT_CORE; unsigned int old_core = NUM_CORES; struct corelock *ocl = NULL; #else const unsigned int core = CURRENT_CORE; #endif struct thread_entry *current = cores[core].running; struct thread_entry *thread = thread_id_entry(thread_id); unsigned state; int oldlevel; if (thread == current) thread_exit(); /* Current thread - do normal exit */ oldlevel = disable_irq_save(); corelock_lock(&thread->waiter_cl); LOCK_THREAD(thread); state = thread->state; if (thread->id != thread_id || state == STATE_KILLED) goto thread_killed; #if NUM_CORES > 1 if (thread->name == THREAD_DESTRUCT) { /* Thread being killed - become a waiter */ UNLOCK_THREAD(thread); corelock_unlock(&thread->waiter_cl); restore_irq(oldlevel); thread_wait(thread_id); return; } thread->name = THREAD_DESTRUCT; /* Slot can't be used for now */ #ifdef HAVE_PRIORITY_SCHEDULING check_for_obj_waiters("remove_thread", thread); #endif if (thread->core != core) { /* Switch cores and safely extract the thread there */ /* Slot HAS to be unlocked or a deadlock could occur which means other * threads have to be guided into becoming thread waiters if they * attempt to remove it. */ unsigned int new_core = thread->core; corelock_unlock(&thread->waiter_cl); UNLOCK_THREAD(thread); restore_irq(oldlevel); old_core = switch_core(new_core); oldlevel = disable_irq_save(); corelock_lock(&thread->waiter_cl); LOCK_THREAD(thread); state = thread->state; core = new_core; /* Perform the extraction and switch ourselves back to the original processor */ } #endif /* NUM_CORES > 1 */ if (thread->tmo.prev != NULL) { /* Clean thread off the timeout list if a timeout check hasn't * run yet */ remove_from_list_tmo(thread); } #ifdef HAVE_SCHEDULER_BOOSTCTRL /* Cancel CPU boost if any */ boost_thread(thread, false); #endif IF_COP( retry_state: ) switch (state) { case STATE_RUNNING: RTR_LOCK(core); /* Remove thread from ready to run tasks */ remove_from_list_l(&cores[core].running, thread); rtr_subtract_entry(core, thread->priority); RTR_UNLOCK(core); break; case STATE_BLOCKED: case STATE_BLOCKED_W_TMO: /* Remove thread from the queue it's blocked on - including its * own if waiting there */ #if NUM_CORES > 1 if (&thread->waiter_cl != thread->obj_cl) { ocl = thread->obj_cl; if (UNLIKELY(corelock_try_lock(ocl) == 0)) { UNLOCK_THREAD(thread); corelock_lock(ocl); LOCK_THREAD(thread); if (UNLIKELY(thread->state != state)) { /* Something woke the thread */ state = thread->state; corelock_unlock(ocl); goto retry_state; } } } #endif remove_from_list_l(thread->bqp, thread); #ifdef HAVE_WAKEUP_EXT_CB if (thread->wakeup_ext_cb != NULL) thread->wakeup_ext_cb(thread); #endif #ifdef HAVE_PRIORITY_SCHEDULING if (thread->blocker != NULL) { /* Remove thread's priority influence from its chain */ wakeup_priority_protocol_release(thread); } #endif #if NUM_CORES > 1 if (ocl != NULL) corelock_unlock(ocl); #endif break; /* Otherwise thread is frozen and hasn't run yet */ } new_thread_id(thread_id, thread); thread->state = STATE_KILLED; /* If thread was waiting on itself, it will have been removed above. * The wrong order would result in waking the thread first and deadlocking * since the slot is already locked. */ thread_queue_wake(&thread->queue); thread->name = NULL; thread_killed: /* Thread was already killed */ /* Removal complete - safe to unlock and reenable interrupts */ corelock_unlock(&thread->waiter_cl); UNLOCK_THREAD(thread); restore_irq(oldlevel); #if NUM_CORES > 1 if (old_core < NUM_CORES) { /* Did a removal on another processor's thread - switch back to native core */ switch_core(old_core); } #endif } #endif /* ALLOW_REMOVE_THREAD */ #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) { int old_base_priority = -1; struct thread_entry *thread = thread_id_entry(thread_id); /* A little safety measure */ if (priority < HIGHEST_PRIORITY || priority > LOWEST_PRIORITY) return -1; /* Thread could be on any list and therefore on an interrupt accessible one - disable interrupts */ int oldlevel = disable_irq_save(); LOCK_THREAD(thread); /* Make sure it's not killed */ if (thread_id == THREAD_ID_CURRENT || (thread->id == thread_id && thread->state != STATE_KILLED)) { int old_priority = thread->priority; old_base_priority = thread->base_priority; thread->base_priority = priority; prio_move_entry(&thread->pdist, old_base_priority, priority); priority = find_first_set_bit(thread->pdist.mask); if (old_priority == priority) { /* No priority change - do nothing */ } else if (thread->state == STATE_RUNNING) { /* This thread is running - change location on the run * queue. No transitive inheritance needed. */ set_running_thread_priority(thread, priority); } else { thread->priority = priority; if (thread->blocker != NULL) { /* Bubble new priority down the chain */ struct blocker *bl = thread->blocker; /* Blocker struct */ struct thread_entry *bl_t = bl->thread; /* Blocking thread */ struct thread_entry * const tstart = thread; /* Initial thread */ const int highest = MIN(priority, old_priority); /* Higher of new or old */ for (;;) { struct thread_entry *next; /* Next thread to check */ int bl_pr; /* Highest blocked thread */ int queue_pr; /* New highest blocked thread */ #if NUM_CORES > 1 /* Owner can change but thread cannot be dislodged - thread * may not be the first in the queue which allows other * threads ahead in the list to be given ownership during the * operation. If thread is next then the waker will have to * wait for us and the owner of the object will remain fixed. * If we successfully grab the owner -- which at some point * is guaranteed -- then the queue remains fixed until we * pass by. */ for (;;) { LOCK_THREAD(bl_t); /* Double-check the owner - retry if it changed */ if (LIKELY(bl->thread == bl_t)) break; UNLOCK_THREAD(bl_t); bl_t = bl->thread; } #endif bl_pr = bl->priority; if (highest > bl_pr) break; /* Object priority won't change */ /* This will include the thread being set */ queue_pr = find_highest_priority_in_list_l(*thread->bqp); if (queue_pr == bl_pr) break; /* Object priority not changing */ /* Update thread boost for this object */ bl->priority = queue_pr; prio_move_entry(&bl_t->pdist, bl_pr, queue_pr); bl_pr = find_first_set_bit(bl_t->pdist.mask); if (bl_t->priority == bl_pr) break; /* Blocking thread priority not changing */ if (bl_t->state == STATE_RUNNING) { /* Thread not blocked - we're done */ set_running_thread_priority(bl_t, bl_pr); break; } bl_t->priority = bl_pr; bl = bl_t->blocker; /* Blocking thread has a blocker? */ if (bl == NULL) break; /* End of chain */ next = bl->thread; if (UNLIKELY(next == tstart)) break; /* Full-circle */ UNLOCK_THREAD(thread); thread = bl_t; bl_t = next; } /* for (;;) */ UNLOCK_THREAD(bl_t); } } } 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_CURRENT && (thread->id != thread_id || thread->state == STATE_KILLED)) base_priority = -1; return base_priority; } #endif /* HAVE_PRIORITY_SCHEDULING */ #ifdef HAVE_IO_PRIORITY int thread_get_io_priority(unsigned int thread_id) { struct thread_entry *thread = thread_id_entry(thread_id); return thread->io_priority; } void thread_set_io_priority(unsigned int thread_id,int io_priority) { struct thread_entry *thread = thread_id_entry(thread_id); thread->io_priority = io_priority; } #endif /*--------------------------------------------------------------------------- * 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); } /*--------------------------------------------------------------------------- * Return the ID of the currently executing thread. *--------------------------------------------------------------------------- */ unsigned int thread_get_current(void) { return cores[CURRENT_CORE].running->id; } #if NUM_CORES > 1 /*--------------------------------------------------------------------------- * Switch the processor that the currently executing thread runs on. *--------------------------------------------------------------------------- */ unsigned int switch_core(unsigned int new_core) { const unsigned int core = CURRENT_CORE; struct thread_entry *current = cores[core].running; if (core == new_core) { /* No change - just return same core */ return core; } int oldlevel = disable_irq_save(); LOCK_THREAD(current); if (current->name == THREAD_DESTRUCT) { /* Thread being killed - deactivate and let process complete */ unsigned int id = current->id; UNLOCK_THREAD(current); restore_irq(oldlevel); thread_wait(id); /* Should never be reached */ THREAD_PANICF("switch_core->D:*R", current); } /* Get us off the running list for the current core */ RTR_LOCK(core); remove_from_list_l(&cores[core].running, current); rtr_subtract_entry(core, current->priority); RTR_UNLOCK(core); /* Stash return value (old core) in a safe place */ current->retval = core; /* If a timeout hadn't yet been cleaned-up it must be removed now or * the other core will likely attempt a removal from the wrong list! */ if (current->tmo.prev != NULL) { remove_from_list_tmo(current); } /* Change the core number for this thread slot */ current->core = new_core; /* Do not use core_schedule_wakeup here since this will result in * the thread starting to run on the other core before being finished on * this one. Delay the list unlock to keep the other core stuck * until this thread is ready. */ RTR_LOCK(new_core); rtr_add_entry(new_core, current->priority); add_to_list_l(&cores[new_core].running, current); /* Make a callback into device-specific code, unlock the wakeup list so * that execution may resume on the new core, unlock our slot and finally * restore the interrupt level */ cores[core].blk_ops.flags = TBOP_SWITCH_CORE; cores[core].blk_ops.cl_p = &cores[new_core].rtr_cl; cores[core].block_task = current; UNLOCK_THREAD(current); /* Alert other core to activity */ core_wake(new_core); /* Do the stack switching, cache_maintenence and switch_thread call - requires native code */ switch_thread_core(core, current); /* Finally return the old core to caller */ return current->retval; } #endif /* NUM_CORES > 1 */ /*--------------------------------------------------------------------------- * 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_threads(void) { const unsigned int core = CURRENT_CORE; struct thread_entry *thread; if (core == CPU) { /* Initialize core locks and IDs in all slots */ int n; for (n = 0; n < MAXTHREADS; n++) { thread = &threads[n]; corelock_init(&thread->waiter_cl); corelock_init(&thread->slot_cl); thread->id = THREAD_ID_INIT(n); } } /* CPU will initialize first and then sleep */ thread = find_empty_thread_slot(); 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); } /* Initialize initially non-zero members of core */ cores[core].next_tmo_check = current_tick; /* Something not in the past */ /* Initialize initially non-zero members of slot */ UNLOCK_THREAD(thread); /* No sync worries yet */ thread->name = main_thread_name; thread->state = STATE_RUNNING; IF_COP( thread->core = core; ) #ifdef HAVE_PRIORITY_SCHEDULING corelock_init(&cores[core].rtr_cl); thread->base_priority = PRIORITY_USER_INTERFACE; prio_add_entry(&thread->pdist, PRIORITY_USER_INTERFACE); thread->priority = PRIORITY_USER_INTERFACE; rtr_add_entry(core, PRIORITY_USER_INTERFACE); #endif add_to_list_l(&cores[core].running, thread); if (core == CPU) { thread->stack = stackbegin; thread->stack_size = (uintptr_t)stackend - (uintptr_t)stackbegin; #if NUM_CORES > 1 /* This code path will not be run on single core targets */ /* 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. */ core_thread_init(CPU); } else { /* Initial stack is the idle stack */ thread->stack = idle_stacks[core]; thread->stack_size = IDLE_STACK_SIZE; /* 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); /* Other cores do not have a main thread - go idle inside switch_thread * until a thread can run on the core. */ thread_exit(); #endif /* NUM_CORES */ } } /* Shared stack scan helper for thread_stack_usage and idle_stack_usage */ #if NUM_CORES == 1 static inline int stack_usage(uintptr_t *stackptr, size_t stack_size) #else static int stack_usage(uintptr_t *stackptr, size_t stack_size) #endif { unsigned int stack_words = stack_size / sizeof (uintptr_t); unsigned int i; int usage = 0; for (i = 0; i < stack_words; i++) { if (stackptr[i] != DEADBEEF) { usage = ((stack_words - i) * 100) / stack_words; break; } } return usage; } /*--------------------------------------------------------------------------- * Returns the maximum percentage of stack a thread ever used while running. * NOTE: Some large buffer allocations that don't use enough the buffer to * overwrite stackptr[0] will not be seen. *--------------------------------------------------------------------------- */ int thread_stack_usage(const struct thread_entry *thread) { return stack_usage(thread->stack, 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) { return stack_usage(idle_stacks[core], IDLE_STACK_SIZE); } #endif /*--------------------------------------------------------------------------- * 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 IF_COP(|| name == THREAD_DESTRUCT) || *name == '\0') { name = (const char *)thread; fmt = "%08lX"; } snprintf(buffer, size, fmt, name); } }