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  1. /*
  2.  * Copyright (C) 2001-2004 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 <atomic.h>
  51. #include <synch/spinlock.h>
  52. #include <config.h>
  53. #include <context.h>
  54. #include <func.h>
  55. #include <arch.h>
  56. #include <adt/list.h>
  57. #include <panic.h>
  58. #include <typedefs.h>
  59. #include <cpu.h>
  60. #include <print.h>
  61. #include <debug.h>
  62.  
  63. static void before_task_runs(void);
  64. static void before_thread_runs(void);
  65. static void after_thread_ran(void);
  66. static void scheduler_separated_stack(void);
  67.  
  68. atomic_t nrdy;  /**< Number of ready threads in the system. */
  69.  
  70. /** Carry out actions before new task runs. */
  71. void before_task_runs(void)
  72. {
  73.     before_task_runs_arch();
  74. }
  75.  
  76. /** Take actions before new thread runs.
  77.  *
  78.  * Perform actions that need to be
  79.  * taken before the newly selected
  80.  * tread is passed control.
  81.  *
  82.  * THREAD->lock is locked on entry
  83.  *
  84.  */
  85. void before_thread_runs(void)
  86. {
  87.     before_thread_runs_arch();
  88. #ifdef CONFIG_FPU_LAZY
  89.     if(THREAD==CPU->fpu_owner)
  90.         fpu_enable();
  91.     else
  92.         fpu_disable();
  93. #else
  94.     fpu_enable();
  95.     if (THREAD->fpu_context_exists)
  96.         fpu_context_restore(THREAD->saved_fpu_context);
  97.     else {
  98.         fpu_init();
  99.         THREAD->fpu_context_exists=1;
  100.     }
  101. #endif
  102. }
  103.  
  104. /** Take actions after THREAD had run.
  105.  *
  106.  * Perform actions that need to be
  107.  * taken after the running thread
  108.  * had been preempted by the scheduler.
  109.  *
  110.  * THREAD->lock is locked on entry
  111.  *
  112.  */
  113. void after_thread_ran(void)
  114. {
  115.     after_thread_ran_arch();
  116. }
  117.  
  118. #ifdef CONFIG_FPU_LAZY
  119. void scheduler_fpu_lazy_request(void)
  120. {
  121. restart:
  122.     fpu_enable();
  123.     spinlock_lock(&CPU->lock);
  124.  
  125.     /* Save old context */
  126.     if (CPU->fpu_owner != NULL) {  
  127.         spinlock_lock(&CPU->fpu_owner->lock);
  128.         fpu_context_save(CPU->fpu_owner->saved_fpu_context);
  129.         /* don't prevent migration */
  130.         CPU->fpu_owner->fpu_context_engaged=0;
  131.         spinlock_unlock(&CPU->fpu_owner->lock);
  132.         CPU->fpu_owner = NULL;
  133.     }
  134.  
  135.     spinlock_lock(&THREAD->lock);
  136.     if (THREAD->fpu_context_exists) {
  137.         fpu_context_restore(THREAD->saved_fpu_context);
  138.     } else {
  139.         /* Allocate FPU context */
  140.         if (!THREAD->saved_fpu_context) {
  141.             /* Might sleep */
  142.             spinlock_unlock(&THREAD->lock);
  143.             spinlock_unlock(&CPU->lock);
  144.             THREAD->saved_fpu_context = slab_alloc(fpu_context_slab,
  145.                                    0);
  146.             /* We may have switched CPUs during slab_alloc */
  147.             goto restart;
  148.         }
  149.         fpu_init();
  150.         THREAD->fpu_context_exists=1;
  151.     }
  152.     CPU->fpu_owner=THREAD;
  153.     THREAD->fpu_context_engaged = 1;
  154.     spinlock_unlock(&THREAD->lock);
  155.  
  156.     spinlock_unlock(&CPU->lock);
  157. }
  158. #endif
  159.  
  160. /** Initialize scheduler
  161.  *
  162.  * Initialize kernel scheduler.
  163.  *
  164.  */
  165. void scheduler_init(void)
  166. {
  167. }
  168.  
  169. /** Get thread to be scheduled
  170.  *
  171.  * Get the optimal thread to be scheduled
  172.  * according to thread accounting and scheduler
  173.  * policy.
  174.  *
  175.  * @return Thread to be scheduled.
  176.  *
  177.  */
  178. static thread_t *find_best_thread(void)
  179. {
  180.     thread_t *t;
  181.     runq_t *r;
  182.     int i;
  183.  
  184.     ASSERT(CPU != NULL);
  185.  
  186. loop:
  187.     interrupts_enable();
  188.    
  189.     if (atomic_get(&CPU->nrdy) == 0) {
  190.         /*
  191.          * For there was nothing to run, the CPU goes to sleep
  192.          * until a hardware interrupt or an IPI comes.
  193.          * This improves energy saving and hyperthreading.
  194.          */
  195.  
  196.         /*
  197.          * An interrupt might occur right now and wake up a thread.
  198.          * In such case, the CPU will continue to go to sleep
  199.          * even though there is a runnable thread.
  200.          */
  201.  
  202.          cpu_sleep();
  203.          goto loop;
  204.     }
  205.  
  206.     interrupts_disable();
  207.    
  208.     for (i = 0; i<RQ_COUNT; i++) {
  209.         r = &CPU->rq[i];
  210.         spinlock_lock(&r->lock);
  211.         if (r->n == 0) {
  212.             /*
  213.              * If this queue is empty, try a lower-priority queue.
  214.              */
  215.             spinlock_unlock(&r->lock);
  216.             continue;
  217.         }
  218.  
  219.         atomic_dec(&CPU->nrdy);
  220.         atomic_dec(&nrdy);
  221.         r->n--;
  222.  
  223.         /*
  224.          * Take the first thread from the queue.
  225.          */
  226.         t = list_get_instance(r->rq_head.next, thread_t, rq_link);
  227.         list_remove(&t->rq_link);
  228.  
  229.         spinlock_unlock(&r->lock);
  230.  
  231.         spinlock_lock(&t->lock);
  232.         t->cpu = CPU;
  233.  
  234.         t->ticks = us2ticks((i+1)*10000);
  235.         t->priority = i;    /* correct rq index */
  236.  
  237.         /*
  238.          * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge.
  239.          */
  240.         t->flags &= ~X_STOLEN;
  241.         spinlock_unlock(&t->lock);
  242.  
  243.         return t;
  244.     }
  245.     goto loop;
  246.  
  247. }
  248.  
  249. /** Prevent rq starvation
  250.  *
  251.  * Prevent low priority threads from starving in rq's.
  252.  *
  253.  * When the function decides to relink rq's, it reconnects
  254.  * respective pointers so that in result threads with 'pri'
  255.  * greater or equal start are moved to a higher-priority queue.
  256.  *
  257.  * @param start Threshold priority.
  258.  *
  259.  */
  260. static void relink_rq(int start)
  261. {
  262.     link_t head;
  263.     runq_t *r;
  264.     int i, n;
  265.  
  266.     list_initialize(&head);
  267.     spinlock_lock(&CPU->lock);
  268.     if (CPU->needs_relink > NEEDS_RELINK_MAX) {
  269.         for (i = start; i<RQ_COUNT-1; i++) {
  270.             /* remember and empty rq[i + 1] */
  271.             r = &CPU->rq[i + 1];
  272.             spinlock_lock(&r->lock);
  273.             list_concat(&head, &r->rq_head);
  274.             n = r->n;
  275.             r->n = 0;
  276.             spinlock_unlock(&r->lock);
  277.        
  278.             /* append rq[i + 1] to rq[i] */
  279.             r = &CPU->rq[i];
  280.             spinlock_lock(&r->lock);
  281.             list_concat(&r->rq_head, &head);
  282.             r->n += n;
  283.             spinlock_unlock(&r->lock);
  284.         }
  285.         CPU->needs_relink = 0;
  286.     }
  287.     spinlock_unlock(&CPU->lock);
  288.  
  289. }
  290.  
  291. /** The scheduler
  292.  *
  293.  * The thread scheduling procedure.
  294.  * Passes control directly to
  295.  * scheduler_separated_stack().
  296.  *
  297.  */
  298. void scheduler(void)
  299. {
  300.     volatile ipl_t ipl;
  301.  
  302.     ASSERT(CPU != NULL);
  303.  
  304.     ipl = interrupts_disable();
  305.  
  306.     if (atomic_get(&haltstate))
  307.         halt();
  308.    
  309.     if (THREAD) {
  310.         spinlock_lock(&THREAD->lock);
  311. #ifndef CONFIG_FPU_LAZY
  312.         fpu_context_save(THREAD->saved_fpu_context);
  313. #endif
  314.         if (!context_save(&THREAD->saved_context)) {
  315.             /*
  316.              * This is the place where threads leave scheduler();
  317.              */
  318.             spinlock_unlock(&THREAD->lock);
  319.             interrupts_restore(THREAD->saved_context.ipl);
  320.            
  321.             return;
  322.         }
  323.  
  324.         /*
  325.          * Interrupt priority level of preempted thread is recorded here
  326.          * to facilitate scheduler() invocations from interrupts_disable()'d
  327.          * code (e.g. waitq_sleep_timeout()).
  328.          */
  329.         THREAD->saved_context.ipl = ipl;
  330.     }
  331.  
  332.     /*
  333.      * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM
  334.      * and preemption counter. At this point THE could be coming either
  335.      * from THREAD's or CPU's stack.
  336.      */
  337.     the_copy(THE, (the_t *) CPU->stack);
  338.  
  339.     /*
  340.      * We may not keep the old stack.
  341.      * Reason: If we kept the old stack and got blocked, for instance, in
  342.      * find_best_thread(), the old thread could get rescheduled by another
  343.      * CPU and overwrite the part of its own stack that was also used by
  344.      * the scheduler on this CPU.
  345.      *
  346.      * Moreover, we have to bypass the compiler-generated POP sequence
  347.      * which is fooled by SP being set to the very top of the stack.
  348.      * Therefore the scheduler() function continues in
  349.      * scheduler_separated_stack().
  350.      */
  351.     context_save(&CPU->saved_context);
  352.     context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (uintptr_t) CPU->stack, CPU_STACK_SIZE);
  353.     context_restore(&CPU->saved_context);
  354.     /* not reached */
  355. }
  356.  
  357. /** Scheduler stack switch wrapper
  358.  *
  359.  * Second part of the scheduler() function
  360.  * using new stack. Handling the actual context
  361.  * switch to a new thread.
  362.  *
  363.  * Assume THREAD->lock is held.
  364.  */
  365. void scheduler_separated_stack(void)
  366. {
  367.     int priority;
  368.    
  369.     ASSERT(CPU != NULL);
  370.    
  371.     if (THREAD) {
  372.         /* must be run after the switch to scheduler stack */
  373.         after_thread_ran();
  374.  
  375.         switch (THREAD->state) {
  376.             case Running:
  377.             spinlock_unlock(&THREAD->lock);
  378.             thread_ready(THREAD);
  379.             break;
  380.  
  381.             case Exiting:
  382. repeat:
  383.                 if (THREAD->detached) {
  384.                 thread_destroy(THREAD);
  385.             } else {
  386.                 /*
  387.                  * The thread structure is kept allocated until somebody
  388.                  * calls thread_detach() on it.
  389.                  */
  390.                 if (!spinlock_trylock(&THREAD->join_wq.lock)) {
  391.                     /*
  392.                      * Avoid deadlock.
  393.                      */
  394.                     spinlock_unlock(&THREAD->lock);
  395.                     delay(10);
  396.                     spinlock_lock(&THREAD->lock);
  397.                     goto repeat;
  398.                 }
  399.                 _waitq_wakeup_unsafe(&THREAD->join_wq, false);
  400.                 spinlock_unlock(&THREAD->join_wq.lock);
  401.                
  402.                 THREAD->state = Undead;
  403.                 spinlock_unlock(&THREAD->lock);
  404.             }
  405.             break;
  406.            
  407.             case Sleeping:
  408.             /*
  409.              * Prefer the thread after it's woken up.
  410.              */
  411.             THREAD->priority = -1;
  412.  
  413.             /*
  414.              * We need to release wq->lock which we locked in waitq_sleep().
  415.              * Address of wq->lock is kept in THREAD->sleep_queue.
  416.              */
  417.             spinlock_unlock(&THREAD->sleep_queue->lock);
  418.  
  419.             /*
  420.              * Check for possible requests for out-of-context invocation.
  421.              */
  422.             if (THREAD->call_me) {
  423.                 THREAD->call_me(THREAD->call_me_with);
  424.                 THREAD->call_me = NULL;
  425.                 THREAD->call_me_with = NULL;
  426.             }
  427.  
  428.             spinlock_unlock(&THREAD->lock);
  429.  
  430.             break;
  431.  
  432.             default:
  433.             /*
  434.              * Entering state is unexpected.
  435.              */
  436.             panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
  437.             break;
  438.         }
  439.  
  440.         THREAD = NULL;
  441.     }
  442.  
  443.     THREAD = find_best_thread();
  444.    
  445.     spinlock_lock(&THREAD->lock);
  446.     priority = THREAD->priority;
  447.     spinlock_unlock(&THREAD->lock);
  448.  
  449.     relink_rq(priority);       
  450.  
  451.     /*
  452.      * If both the old and the new task are the same, lots of work is avoided.
  453.      */
  454.     if (TASK != THREAD->task) {
  455.         as_t *as1 = NULL;
  456.         as_t *as2;
  457.  
  458.         if (TASK) {
  459.             spinlock_lock(&TASK->lock);
  460.             as1 = TASK->as;
  461.             spinlock_unlock(&TASK->lock);
  462.         }
  463.  
  464.         spinlock_lock(&THREAD->task->lock);
  465.         as2 = THREAD->task->as;
  466.         spinlock_unlock(&THREAD->task->lock);
  467.        
  468.         /*
  469.          * Note that it is possible for two tasks to share one address space.
  470.          */
  471.         if (as1 != as2) {
  472.             /*
  473.              * Both tasks and address spaces are different.
  474.              * Replace the old one with the new one.
  475.              */
  476.             as_switch(as1, as2);
  477.         }
  478.         TASK = THREAD->task;
  479.         before_task_runs();
  480.     }
  481.  
  482.     spinlock_lock(&THREAD->lock);  
  483.     THREAD->state = Running;
  484.  
  485. #ifdef SCHEDULER_VERBOSE
  486.     printf("cpu%d: tid %d (priority=%d,ticks=%lld,nrdy=%ld)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, atomic_get(&CPU->nrdy));
  487. #endif 
  488.  
  489.     /*
  490.      * Some architectures provide late kernel PA2KA(identity)
  491.      * mapping in a page fault handler. However, the page fault
  492.      * handler uses the kernel stack of the running thread and
  493.      * therefore cannot be used to map it. The kernel stack, if
  494.      * necessary, is to be mapped in before_thread_runs(). This
  495.      * function must be executed before the switch to the new stack.
  496.      */
  497.     before_thread_runs();
  498.  
  499.     /*
  500.      * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
  501.      */
  502.     the_copy(THE, (the_t *) THREAD->kstack);
  503.    
  504.     context_restore(&THREAD->saved_context);
  505.     /* not reached */
  506. }
  507.  
  508. #ifdef CONFIG_SMP
  509. /** Load balancing thread
  510.  *
  511.  * SMP load balancing thread, supervising thread supplies
  512.  * for the CPU it's wired to.
  513.  *
  514.  * @param arg Generic thread argument (unused).
  515.  *
  516.  */
  517. void kcpulb(void *arg)
  518. {
  519.     thread_t *t;
  520.     int count, average, i, j, k = 0;
  521.     ipl_t ipl;
  522.  
  523.     /*
  524.      * Detach kcpulb as nobody will call thread_join_timeout() on it.
  525.      */
  526.     thread_detach(THREAD);
  527.    
  528. loop:
  529.     /*
  530.      * Work in 1s intervals.
  531.      */
  532.     thread_sleep(1);
  533.  
  534. not_satisfied:
  535.     /*
  536.      * Calculate the number of threads that will be migrated/stolen from
  537.      * other CPU's. Note that situation can have changed between two
  538.      * passes. Each time get the most up to date counts.
  539.      */
  540.     average = atomic_get(&nrdy) / config.cpu_active + 1;
  541.     count = average - atomic_get(&CPU->nrdy);
  542.  
  543.     if (count <= 0)
  544.         goto satisfied;
  545.  
  546.     /*
  547.      * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
  548.      */
  549.     for (j=RQ_COUNT-1; j >= 0; j--) {
  550.         for (i=0; i < config.cpu_active; i++) {
  551.             link_t *l;
  552.             runq_t *r;
  553.             cpu_t *cpu;
  554.  
  555.             cpu = &cpus[(i + k) % config.cpu_active];
  556.  
  557.             /*
  558.              * Not interested in ourselves.
  559.              * Doesn't require interrupt disabling for kcpulb is X_WIRED.
  560.              */
  561.             if (CPU == cpu)
  562.                 continue;
  563.             if (atomic_get(&cpu->nrdy) <= average)
  564.                 continue;
  565.  
  566.             ipl = interrupts_disable();
  567.             r = &cpu->rq[j];
  568.             spinlock_lock(&r->lock);
  569.             if (r->n == 0) {
  570.                 spinlock_unlock(&r->lock);
  571.                 interrupts_restore(ipl);
  572.                 continue;
  573.             }
  574.        
  575.             t = NULL;
  576.             l = r->rq_head.prev;    /* search rq from the back */
  577.             while (l != &r->rq_head) {
  578.                 t = list_get_instance(l, thread_t, rq_link);
  579.                 /*
  580.                  * We don't want to steal CPU-wired threads neither threads already stolen.
  581.                  * The latter prevents threads from migrating between CPU's without ever being run.
  582.                  * We don't want to steal threads whose FPU context is still in CPU.
  583.                  */
  584.                 spinlock_lock(&t->lock);
  585.                 if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
  586.                     /*
  587.                      * Remove t from r.
  588.                      */
  589.                     spinlock_unlock(&t->lock);
  590.                    
  591.                     atomic_dec(&cpu->nrdy);
  592.                     atomic_dec(&nrdy);
  593.  
  594.                     r->n--;
  595.                     list_remove(&t->rq_link);
  596.  
  597.                     break;
  598.                 }
  599.                 spinlock_unlock(&t->lock);
  600.                 l = l->prev;
  601.                 t = NULL;
  602.             }
  603.             spinlock_unlock(&r->lock);
  604.  
  605.             if (t) {
  606.                 /*
  607.                  * Ready t on local CPU
  608.                  */
  609.                 spinlock_lock(&t->lock);
  610. #ifdef KCPULB_VERBOSE
  611.                 printf("kcpulb%d: TID %d -> cpu%d, nrdy=%ld, avg=%nd\n", CPU->id, t->tid, CPU->id, atomic_get(&CPU->nrdy), atomic_get(&nrdy) / config.cpu_active);
  612. #endif
  613.                 t->flags |= X_STOLEN;
  614.                 t->state = Entering;
  615.                 spinlock_unlock(&t->lock);
  616.    
  617.                 thread_ready(t);
  618.  
  619.                 interrupts_restore(ipl);
  620.    
  621.                 if (--count == 0)
  622.                     goto satisfied;
  623.                    
  624.                 /*
  625.                  * We are not satisfied yet, focus on another CPU next time.
  626.                  */
  627.                 k++;
  628.                
  629.                 continue;
  630.             }
  631.             interrupts_restore(ipl);
  632.         }
  633.     }
  634.  
  635.     if (atomic_get(&CPU->nrdy)) {
  636.         /*
  637.          * Be a little bit light-weight and let migrated threads run.
  638.          */
  639.         scheduler();
  640.     } else {
  641.         /*
  642.          * We failed to migrate a single thread.
  643.          * Give up this turn.
  644.          */
  645.         goto loop;
  646.     }
  647.        
  648.     goto not_satisfied;
  649.  
  650. satisfied:
  651.     goto loop;
  652. }
  653.  
  654. #endif /* CONFIG_SMP */
  655.  
  656.  
  657. /** Print information about threads & scheduler queues */
  658. void sched_print_list(void)
  659. {
  660.     ipl_t ipl;
  661.     int cpu,i;
  662.     runq_t *r;
  663.     thread_t *t;
  664.     link_t *cur;
  665.  
  666.     /* We are going to mess with scheduler structures,
  667.      * let's not be interrupted */
  668.     ipl = interrupts_disable();
  669.     for (cpu=0;cpu < config.cpu_count; cpu++) {
  670.  
  671.         if (!cpus[cpu].active)
  672.             continue;
  673.  
  674.         spinlock_lock(&cpus[cpu].lock);
  675.         printf("cpu%d: address=%p, nrdy=%ld, needs_relink=%ld\n",
  676.                cpus[cpu].id, &cpus[cpu], atomic_get(&cpus[cpu].nrdy), cpus[cpu].needs_relink);
  677.        
  678.         for (i=0; i<RQ_COUNT; i++) {
  679.             r = &cpus[cpu].rq[i];
  680.             spinlock_lock(&r->lock);
  681.             if (!r->n) {
  682.                 spinlock_unlock(&r->lock);
  683.                 continue;
  684.             }
  685.             printf("\trq[%d]: ", i);
  686.             for (cur=r->rq_head.next; cur!=&r->rq_head; cur=cur->next) {
  687.                 t = list_get_instance(cur, thread_t, rq_link);
  688.                 printf("%d(%s) ", t->tid,
  689.                        thread_states[t->state]);
  690.             }
  691.             printf("\n");
  692.             spinlock_unlock(&r->lock);
  693.         }
  694.         spinlock_unlock(&cpus[cpu].lock);
  695.     }
  696.    
  697.     interrupts_restore(ipl);
  698. }
  699.  
  700. /** @}
  701.  */
  702.