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