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  1. /*
  2.  * Copyright (c) 2001-2007 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup genericproc
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief   Scheduler and load balancing.
  36.  *
  37.  * This file contains the scheduler and kcpulb kernel thread which
  38.  * performs load-balancing of per-CPU run queues.
  39.  */
  40.  
  41. #include <proc/scheduler.h>
  42. #include <proc/thread.h>
  43. #include <proc/task.h>
  44. #include <mm/frame.h>
  45. #include <mm/page.h>
  46. #include <mm/as.h>
  47. #include <time/timeout.h>
  48. #include <time/delay.h>
  49. #include <arch/asm.h>
  50. #include <arch/faddr.h>
  51. #include <arch/cycle.h>
  52. #include <atomic.h>
  53. #include <synch/spinlock.h>
  54. #include <config.h>
  55. #include <context.h>
  56. #include <fpu_context.h>
  57. #include <func.h>
  58. #include <arch.h>
  59. #include <adt/list.h>
  60. #include <panic.h>
  61. #include <cpu.h>
  62. #include <print.h>
  63. #include <debug.h>
  64.  
  65. static void before_task_runs(void);
  66. static void before_thread_runs(void);
  67. static void after_thread_ran(void);
  68. static void scheduler_separated_stack(void);
  69.  
  70. atomic_t nrdy;  /**< Number of ready threads in the system. */
  71.  
  72. /** Carry out actions before new task runs. */
  73. void before_task_runs(void)
  74. {
  75.     before_task_runs_arch();
  76. }
  77.  
  78. /** Take actions before new thread runs.
  79.  *
  80.  * Perform actions that need to be
  81.  * taken before the newly selected
  82.  * tread is passed control.
  83.  *
  84.  * THREAD->lock is locked on entry
  85.  *
  86.  */
  87. void before_thread_runs(void)
  88. {
  89.     before_thread_runs_arch();
  90. #ifdef CONFIG_FPU_LAZY
  91.     if(THREAD == CPU->fpu_owner)
  92.         fpu_enable();
  93.     else
  94.         fpu_disable();
  95. #else
  96.     fpu_enable();
  97.     if (THREAD->fpu_context_exists)
  98.         fpu_context_restore(THREAD->saved_fpu_context);
  99.     else {
  100.         fpu_init();
  101.         THREAD->fpu_context_exists = 1;
  102.     }
  103. #endif
  104. }
  105.  
  106. /** Take actions after THREAD had run.
  107.  *
  108.  * Perform actions that need to be
  109.  * taken after the running thread
  110.  * had been preempted by the scheduler.
  111.  *
  112.  * THREAD->lock is locked on entry
  113.  *
  114.  */
  115. void after_thread_ran(void)
  116. {
  117.     after_thread_ran_arch();
  118. }
  119.  
  120. #ifdef CONFIG_FPU_LAZY
  121. void scheduler_fpu_lazy_request(void)
  122. {
  123. restart:
  124.     fpu_enable();
  125.     spinlock_lock(&CPU->lock);
  126.  
  127.     /* Save old context */
  128.     if (CPU->fpu_owner != NULL) {  
  129.         spinlock_lock(&CPU->fpu_owner->lock);
  130.         fpu_context_save(CPU->fpu_owner->saved_fpu_context);
  131.         /* don't prevent migration */
  132.         CPU->fpu_owner->fpu_context_engaged = 0;
  133.         spinlock_unlock(&CPU->fpu_owner->lock);
  134.         CPU->fpu_owner = NULL;
  135.     }
  136.  
  137.     spinlock_lock(&THREAD->lock);
  138.     if (THREAD->fpu_context_exists) {
  139.         fpu_context_restore(THREAD->saved_fpu_context);
  140.     } else {
  141.         /* Allocate FPU context */
  142.         if (!THREAD->saved_fpu_context) {
  143.             /* Might sleep */
  144.             spinlock_unlock(&THREAD->lock);
  145.             spinlock_unlock(&CPU->lock);
  146.             THREAD->saved_fpu_context =
  147.                 (fpu_context_t *) slab_alloc(fpu_context_slab, 0);
  148.             /* We may have switched CPUs during slab_alloc */
  149.             goto restart;
  150.         }
  151.         fpu_init();
  152.         THREAD->fpu_context_exists = 1;
  153.     }
  154.     CPU->fpu_owner = THREAD;
  155.     THREAD->fpu_context_engaged = 1;
  156.     spinlock_unlock(&THREAD->lock);
  157.  
  158.     spinlock_unlock(&CPU->lock);
  159. }
  160. #endif
  161.  
  162. /** Initialize scheduler
  163.  *
  164.  * Initialize kernel scheduler.
  165.  *
  166.  */
  167. void scheduler_init(void)
  168. {
  169. }
  170.  
  171. /** Get thread to be scheduled
  172.  *
  173.  * Get the optimal thread to be scheduled
  174.  * according to thread accounting and scheduler
  175.  * policy.
  176.  *
  177.  * @return Thread to be scheduled.
  178.  *
  179.  */
  180. static thread_t *find_best_thread(void)
  181. {
  182.     thread_t *t;
  183.     runq_t *r;
  184.     int i;
  185.  
  186.     ASSERT(CPU != NULL);
  187.  
  188. loop:
  189.     interrupts_enable();
  190.    
  191.     if (atomic_get(&CPU->nrdy) == 0) {
  192.         /*
  193.          * For there was nothing to run, the CPU goes to sleep
  194.          * until a hardware interrupt or an IPI comes.
  195.          * This improves energy saving and hyperthreading.
  196.          */
  197.  
  198.         /*
  199.          * An interrupt might occur right now and wake up a thread.
  200.          * In such case, the CPU will continue to go to sleep
  201.          * even though there is a runnable thread.
  202.          */
  203.  
  204.          cpu_sleep();
  205.          goto loop;
  206.     }
  207.  
  208.     interrupts_disable();
  209.    
  210.     for (i = 0; i < RQ_COUNT; i++) {
  211.         r = &CPU->rq[i];
  212.         spinlock_lock(&r->lock);
  213.         if (r->n == 0) {
  214.             /*
  215.              * If this queue is empty, try a lower-priority queue.
  216.              */
  217.             spinlock_unlock(&r->lock);
  218.             continue;
  219.         }
  220.  
  221.         atomic_dec(&CPU->nrdy);
  222.         atomic_dec(&nrdy);
  223.         r->n--;
  224.  
  225.         /*
  226.          * Take the first thread from the queue.
  227.          */
  228.         t = list_get_instance(r->rq_head.next, thread_t, rq_link);
  229.         list_remove(&t->rq_link);
  230.  
  231.         spinlock_unlock(&r->lock);
  232.  
  233.         spinlock_lock(&t->lock);
  234.         t->cpu = CPU;
  235.  
  236.         t->ticks = us2ticks((i + 1) * 10000);
  237.         t->priority = i;    /* correct rq index */
  238.  
  239.         /*
  240.          * Clear the THREAD_FLAG_STOLEN flag so that t can be migrated
  241.          * when load balancing needs emerge.
  242.          */
  243.         t->flags &= ~THREAD_FLAG_STOLEN;
  244.         spinlock_unlock(&t->lock);
  245.  
  246.         return t;
  247.     }
  248.     goto loop;
  249.  
  250. }
  251.  
  252. /** Prevent rq starvation
  253.  *
  254.  * Prevent low priority threads from starving in rq's.
  255.  *
  256.  * When the function decides to relink rq's, it reconnects
  257.  * respective pointers so that in result threads with 'pri'
  258.  * greater or equal start are moved to a higher-priority queue.
  259.  *
  260.  * @param start Threshold priority.
  261.  *
  262.  */
  263. static void relink_rq(int start)
  264. {
  265.     link_t head;
  266.     runq_t *r;
  267.     int i, n;
  268.  
  269.     list_initialize(&head);
  270.     spinlock_lock(&CPU->lock);
  271.     if (CPU->needs_relink > NEEDS_RELINK_MAX) {
  272.         for (i = start; i < RQ_COUNT - 1; i++) {
  273.             /* remember and empty rq[i + 1] */
  274.             r = &CPU->rq[i + 1];
  275.             spinlock_lock(&r->lock);
  276.             list_concat(&head, &r->rq_head);
  277.             n = r->n;
  278.             r->n = 0;
  279.             spinlock_unlock(&r->lock);
  280.        
  281.             /* append rq[i + 1] to rq[i] */
  282.             r = &CPU->rq[i];
  283.             spinlock_lock(&r->lock);
  284.             list_concat(&r->rq_head, &head);
  285.             r->n += n;
  286.             spinlock_unlock(&r->lock);
  287.         }
  288.         CPU->needs_relink = 0;
  289.     }
  290.     spinlock_unlock(&CPU->lock);
  291.  
  292. }
  293.  
  294. /** The scheduler
  295.  *
  296.  * The thread scheduling procedure.
  297.  * Passes control directly to
  298.  * scheduler_separated_stack().
  299.  *
  300.  */
  301. void scheduler(void)
  302. {
  303.     volatile ipl_t ipl;
  304.  
  305.     ASSERT(CPU != NULL);
  306.  
  307.     ipl = interrupts_disable();
  308.  
  309.     if (atomic_get(&haltstate))
  310.         halt();
  311.    
  312.     if (THREAD) {
  313.         spinlock_lock(&THREAD->lock);
  314.        
  315.         /* Update thread accounting */
  316.         THREAD->cycles += get_cycle() - THREAD->last_cycle;
  317.        
  318. #ifndef CONFIG_FPU_LAZY
  319.         fpu_context_save(THREAD->saved_fpu_context);
  320. #endif
  321.         if (!context_save(&THREAD->saved_context)) {
  322.             /*
  323.              * This is the place where threads leave scheduler();
  324.              */
  325.            
  326.             /* Save current CPU cycle */
  327.             THREAD->last_cycle = get_cycle();
  328.            
  329.             spinlock_unlock(&THREAD->lock);
  330.             interrupts_restore(THREAD->saved_context.ipl);
  331.            
  332.             return;
  333.         }
  334.  
  335.         /*
  336.          * Interrupt priority level of preempted thread is recorded
  337.          * here to facilitate scheduler() invocations from
  338.          * interrupts_disable()'d code (e.g. waitq_sleep_timeout()).
  339.          */
  340.         THREAD->saved_context.ipl = ipl;
  341.     }
  342.  
  343.     /*
  344.      * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM
  345.      * and preemption counter. At this point THE could be coming either
  346.      * from THREAD's or CPU's stack.
  347.      */
  348.     the_copy(THE, (the_t *) CPU->stack);
  349.  
  350.     /*
  351.      * We may not keep the old stack.
  352.      * Reason: If we kept the old stack and got blocked, for instance, in
  353.      * find_best_thread(), the old thread could get rescheduled by another
  354.      * CPU and overwrite the part of its own stack that was also used by
  355.      * the scheduler on this CPU.
  356.      *
  357.      * Moreover, we have to bypass the compiler-generated POP sequence
  358.      * which is fooled by SP being set to the very top of the stack.
  359.      * Therefore the scheduler() function continues in
  360.      * scheduler_separated_stack().
  361.      */
  362.     context_save(&CPU->saved_context);
  363.     context_set(&CPU->saved_context, FADDR(scheduler_separated_stack),
  364.         (uintptr_t) CPU->stack, CPU_STACK_SIZE);
  365.     context_restore(&CPU->saved_context);
  366.     /* not reached */
  367. }
  368.  
  369. /** Scheduler stack switch wrapper
  370.  *
  371.  * Second part of the scheduler() function
  372.  * using new stack. Handling the actual context
  373.  * switch to a new thread.
  374.  *
  375.  * Assume THREAD->lock is held.
  376.  */
  377. void scheduler_separated_stack(void)
  378. {
  379.     int priority;
  380.     DEADLOCK_PROBE_INIT(p_joinwq);
  381.  
  382.     ASSERT(CPU != NULL);
  383.    
  384.     if (THREAD) {
  385.         /* must be run after the switch to scheduler stack */
  386.         after_thread_ran();
  387.  
  388.         switch (THREAD->state) {
  389.         case Running:
  390.             spinlock_unlock(&THREAD->lock);
  391.             thread_ready(THREAD);
  392.             break;
  393.  
  394.         case Exiting:
  395. repeat:
  396.             if (THREAD->detached) {
  397.                 thread_destroy(THREAD);
  398.             } else {
  399.                 /*
  400.                  * The thread structure is kept allocated until
  401.                  * somebody calls thread_detach() on it.
  402.                  */
  403.                 if (!spinlock_trylock(&THREAD->join_wq.lock)) {
  404.                     /*
  405.                      * Avoid deadlock.
  406.                      */
  407.                     spinlock_unlock(&THREAD->lock);
  408.                     delay(10);
  409.                     spinlock_lock(&THREAD->lock);
  410.                     DEADLOCK_PROBE(p_joinwq,
  411.                         DEADLOCK_THRESHOLD);
  412.                     goto repeat;
  413.                 }
  414.                 _waitq_wakeup_unsafe(&THREAD->join_wq, false);
  415.                 spinlock_unlock(&THREAD->join_wq.lock);
  416.                
  417.                 THREAD->state = Undead;
  418.                 spinlock_unlock(&THREAD->lock);
  419.             }
  420.             break;
  421.            
  422.         case Sleeping:
  423.             /*
  424.              * Prefer the thread after it's woken up.
  425.              */
  426.             THREAD->priority = -1;
  427.  
  428.             /*
  429.              * We need to release wq->lock which we locked in
  430.              * waitq_sleep(). Address of wq->lock is kept in
  431.              * THREAD->sleep_queue.
  432.              */
  433.             spinlock_unlock(&THREAD->sleep_queue->lock);
  434.  
  435.             /*
  436.              * Check for possible requests for out-of-context
  437.              * invocation.
  438.              */
  439.             if (THREAD->call_me) {
  440.                 THREAD->call_me(THREAD->call_me_with);
  441.                 THREAD->call_me = NULL;
  442.                 THREAD->call_me_with = NULL;
  443.             }
  444.  
  445.             spinlock_unlock(&THREAD->lock);
  446.  
  447.             break;
  448.  
  449.         default:
  450.             /*
  451.              * Entering state is unexpected.
  452.              */
  453.             panic("tid%llu: unexpected state %s\n", THREAD->tid,
  454.                 thread_states[THREAD->state]);
  455.             break;
  456.         }
  457.  
  458.         THREAD = NULL;
  459.     }
  460.  
  461.     THREAD = find_best_thread();
  462.    
  463.     spinlock_lock(&THREAD->lock);
  464.     priority = THREAD->priority;
  465.     spinlock_unlock(&THREAD->lock);
  466.  
  467.     relink_rq(priority);       
  468.  
  469.     /*
  470.      * If both the old and the new task are the same, lots of work is
  471.      * avoided.
  472.      */
  473.     if (TASK != THREAD->task) {
  474.         as_t *as1 = NULL;
  475.         as_t *as2;
  476.  
  477.         if (TASK) {
  478.             spinlock_lock(&TASK->lock);
  479.             as1 = TASK->as;
  480.             spinlock_unlock(&TASK->lock);
  481.         }
  482.  
  483.         spinlock_lock(&THREAD->task->lock);
  484.         as2 = THREAD->task->as;
  485.         spinlock_unlock(&THREAD->task->lock);
  486.        
  487.         /*
  488.          * Note that it is possible for two tasks to share one address
  489.          * space.
  490.          */
  491.         if (as1 != as2) {
  492.             /*
  493.              * Both tasks and address spaces are different.
  494.              * Replace the old one with the new one.
  495.              */
  496.             as_switch(as1, as2);
  497.         }
  498.         TASK = THREAD->task;
  499.         before_task_runs();
  500.     }
  501.  
  502.     spinlock_lock(&THREAD->lock);  
  503.     THREAD->state = Running;
  504.  
  505. #ifdef SCHEDULER_VERBOSE
  506.     printf("cpu%d: tid %llu (priority=%d, ticks=%llu, nrdy=%ld)\n",
  507.         CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks,
  508.         atomic_get(&CPU->nrdy));
  509. #endif 
  510.  
  511.     /*
  512.      * Some architectures provide late kernel PA2KA(identity)
  513.      * mapping in a page fault handler. However, the page fault
  514.      * handler uses the kernel stack of the running thread and
  515.      * therefore cannot be used to map it. The kernel stack, if
  516.      * necessary, is to be mapped in before_thread_runs(). This
  517.      * function must be executed before the switch to the new stack.
  518.      */
  519.     before_thread_runs();
  520.  
  521.     /*
  522.      * Copy the knowledge of CPU, TASK, THREAD and preemption counter to
  523.      * thread's stack.
  524.      */
  525.     the_copy(THE, (the_t *) THREAD->kstack);
  526.    
  527.     context_restore(&THREAD->saved_context);
  528.     /* not reached */
  529. }
  530.  
  531. #ifdef CONFIG_SMP
  532. /** Load balancing thread
  533.  *
  534.  * SMP load balancing thread, supervising thread supplies
  535.  * for the CPU it's wired to.
  536.  *
  537.  * @param arg Generic thread argument (unused).
  538.  *
  539.  */
  540. void kcpulb(void *arg)
  541. {
  542.     thread_t *t;
  543.     int count, average, j, k = 0;
  544.     unsigned int i;
  545.     ipl_t ipl;
  546.  
  547.     /*
  548.      * Detach kcpulb as nobody will call thread_join_timeout() on it.
  549.      */
  550.     thread_detach(THREAD);
  551.    
  552. loop:
  553.     /*
  554.      * Work in 1s intervals.
  555.      */
  556.     thread_sleep(1);
  557.  
  558. not_satisfied:
  559.     /*
  560.      * Calculate the number of threads that will be migrated/stolen from
  561.      * other CPU's. Note that situation can have changed between two
  562.      * passes. Each time get the most up to date counts.
  563.      */
  564.     average = atomic_get(&nrdy) / config.cpu_active + 1;
  565.     count = average - atomic_get(&CPU->nrdy);
  566.  
  567.     if (count <= 0)
  568.         goto satisfied;
  569.  
  570.     /*
  571.      * Searching least priority queues on all CPU's first and most priority
  572.      * queues on all CPU's last.
  573.      */
  574.     for (j = RQ_COUNT - 1; j >= 0; j--) {
  575.         for (i = 0; i < config.cpu_active; i++) {
  576.             link_t *l;
  577.             runq_t *r;
  578.             cpu_t *cpu;
  579.  
  580.             cpu = &cpus[(i + k) % config.cpu_active];
  581.  
  582.             /*
  583.              * Not interested in ourselves.
  584.              * Doesn't require interrupt disabling for kcpulb has
  585.              * THREAD_FLAG_WIRED.
  586.              */
  587.             if (CPU == cpu)
  588.                 continue;
  589.             if (atomic_get(&cpu->nrdy) <= average)
  590.                 continue;
  591.  
  592.             ipl = interrupts_disable();
  593.             r = &cpu->rq[j];
  594.             spinlock_lock(&r->lock);
  595.             if (r->n == 0) {
  596.                 spinlock_unlock(&r->lock);
  597.                 interrupts_restore(ipl);
  598.                 continue;
  599.             }
  600.        
  601.             t = NULL;
  602.             l = r->rq_head.prev;    /* search rq from the back */
  603.             while (l != &r->rq_head) {
  604.                 t = list_get_instance(l, thread_t, rq_link);
  605.                 /*
  606.                  * We don't want to steal CPU-wired threads
  607.                  * neither threads already stolen. The latter
  608.                  * prevents threads from migrating between CPU's
  609.                  * without ever being run. We don't want to
  610.                  * steal threads whose FPU context is still in
  611.                  * CPU.
  612.                  */
  613.                 spinlock_lock(&t->lock);
  614.                 if ((!(t->flags & (THREAD_FLAG_WIRED |
  615.                     THREAD_FLAG_STOLEN))) &&
  616.                     (!(t->fpu_context_engaged))) {
  617.                     /*
  618.                      * Remove t from r.
  619.                      */
  620.                     spinlock_unlock(&t->lock);
  621.                    
  622.                     atomic_dec(&cpu->nrdy);
  623.                     atomic_dec(&nrdy);
  624.  
  625.                     r->n--;
  626.                     list_remove(&t->rq_link);
  627.  
  628.                     break;
  629.                 }
  630.                 spinlock_unlock(&t->lock);
  631.                 l = l->prev;
  632.                 t = NULL;
  633.             }
  634.             spinlock_unlock(&r->lock);
  635.  
  636.             if (t) {
  637.                 /*
  638.                  * Ready t on local CPU
  639.                  */
  640.                 spinlock_lock(&t->lock);
  641. #ifdef KCPULB_VERBOSE
  642.                 printf("kcpulb%d: TID %llu -> cpu%d, nrdy=%ld, "
  643.                     "avg=%nd\n", CPU->id, t->tid, CPU->id,
  644.                     atomic_get(&CPU->nrdy),
  645.                     atomic_get(&nrdy) / config.cpu_active);
  646. #endif
  647.                 t->flags |= THREAD_FLAG_STOLEN;
  648.                 t->state = Entering;
  649.                 spinlock_unlock(&t->lock);
  650.    
  651.                 thread_ready(t);
  652.  
  653.                 interrupts_restore(ipl);
  654.    
  655.                 if (--count == 0)
  656.                     goto satisfied;
  657.                    
  658.                 /*
  659.                  * We are not satisfied yet, focus on another
  660.                  * CPU next time.
  661.                  */
  662.                 k++;
  663.                
  664.                 continue;
  665.             }
  666.             interrupts_restore(ipl);
  667.         }
  668.     }
  669.  
  670.     if (atomic_get(&CPU->nrdy)) {
  671.         /*
  672.          * Be a little bit light-weight and let migrated threads run.
  673.          */
  674.         scheduler();
  675.     } else {
  676.         /*
  677.          * We failed to migrate a single thread.
  678.          * Give up this turn.
  679.          */
  680.         goto loop;
  681.     }
  682.        
  683.     goto not_satisfied;
  684.  
  685. satisfied:
  686.     goto loop;
  687. }
  688.  
  689. #endif /* CONFIG_SMP */
  690.  
  691.  
  692. /** Print information about threads & scheduler queues */
  693. void sched_print_list(void)
  694. {
  695.     ipl_t ipl;
  696.     unsigned int cpu, i;
  697.     runq_t *r;
  698.     thread_t *t;
  699.     link_t *cur;
  700.  
  701.     /* We are going to mess with scheduler structures,
  702.      * let's not be interrupted */
  703.     ipl = interrupts_disable();
  704.     for (cpu = 0; cpu < config.cpu_count; cpu++) {
  705.  
  706.         if (!cpus[cpu].active)
  707.             continue;
  708.  
  709.         spinlock_lock(&cpus[cpu].lock);
  710.         printf("cpu%d: address=%p, nrdy=%ld, needs_relink=%ld\n",
  711.             cpus[cpu].id, &cpus[cpu], atomic_get(&cpus[cpu].nrdy),
  712.             cpus[cpu].needs_relink);
  713.        
  714.         for (i = 0; i < RQ_COUNT; i++) {
  715.             r = &cpus[cpu].rq[i];
  716.             spinlock_lock(&r->lock);
  717.             if (!r->n) {
  718.                 spinlock_unlock(&r->lock);
  719.                 continue;
  720.             }
  721.             printf("\trq[%d]: ", i);
  722.             for (cur = r->rq_head.next; cur != &r->rq_head;
  723.                 cur = cur->next) {
  724.                 t = list_get_instance(cur, thread_t, rq_link);
  725.                 printf("%llu(%s) ", t->tid,
  726.                     thread_states[t->state]);
  727.             }
  728.             printf("\n");
  729.             spinlock_unlock(&r->lock);
  730.         }
  731.         spinlock_unlock(&cpus[cpu].lock);
  732.     }
  733.    
  734.     interrupts_restore(ipl);
  735. }
  736.  
  737. /** @}
  738.  */
  739.