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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.  
  30.  /** @addtogroup genericproc
  31.  * @{
  32.  */
  33.  
  34. /**
  35.  * @file
  36.  * @brief   Scheduler and load balancing.
  37.  *
  38.  * This file contains the scheduler and kcpulb kernel thread which
  39.  * performs load-balancing of per-CPU run queues.
  40.  */
  41.  
  42. #include <proc/scheduler.h>
  43. #include <proc/thread.h>
  44. #include <proc/task.h>
  45. #include <mm/frame.h>
  46. #include <mm/page.h>
  47. #include <mm/as.h>
  48. #include <time/delay.h>
  49. #include <arch/asm.h>
  50. #include <arch/faddr.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 = slab_alloc(fpu_context_slab,
  146.                                    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 X_STOLEN flag so that t can be migrated when load balancing needs emerge.
  240.          */
  241.         t->flags &= ~X_STOLEN;
  242.         spinlock_unlock(&t->lock);
  243.  
  244.         return t;
  245.     }
  246.     goto loop;
  247.  
  248. }
  249.  
  250. /** Prevent rq starvation
  251.  *
  252.  * Prevent low priority threads from starving in rq's.
  253.  *
  254.  * When the function decides to relink rq's, it reconnects
  255.  * respective pointers so that in result threads with 'pri'
  256.  * greater or equal @start are moved to a higher-priority queue.
  257.  *
  258.  * @param start Threshold priority.
  259.  *
  260.  */
  261. static void relink_rq(int start)
  262. {
  263.     link_t head;
  264.     runq_t *r;
  265.     int i, n;
  266.  
  267.     list_initialize(&head);
  268.     spinlock_lock(&CPU->lock);
  269.     if (CPU->needs_relink > NEEDS_RELINK_MAX) {
  270.         for (i = start; i<RQ_COUNT-1; i++) {
  271.             /* remember and empty rq[i + 1] */
  272.             r = &CPU->rq[i + 1];
  273.             spinlock_lock(&r->lock);
  274.             list_concat(&head, &r->rq_head);
  275.             n = r->n;
  276.             r->n = 0;
  277.             spinlock_unlock(&r->lock);
  278.        
  279.             /* append rq[i + 1] to rq[i] */
  280.             r = &CPU->rq[i];
  281.             spinlock_lock(&r->lock);
  282.             list_concat(&r->rq_head, &head);
  283.             r->n += n;
  284.             spinlock_unlock(&r->lock);
  285.         }
  286.         CPU->needs_relink = 0;
  287.     }
  288.     spinlock_unlock(&CPU->lock);
  289.  
  290. }
  291.  
  292. /** The scheduler
  293.  *
  294.  * The thread scheduling procedure.
  295.  * Passes control directly to
  296.  * scheduler_separated_stack().
  297.  *
  298.  */
  299. void scheduler(void)
  300. {
  301.     volatile ipl_t ipl;
  302.  
  303.     ASSERT(CPU != NULL);
  304.  
  305.     ipl = interrupts_disable();
  306.  
  307.     if (atomic_get(&haltstate))
  308.         halt();
  309.    
  310.     if (THREAD) {
  311.         spinlock_lock(&THREAD->lock);
  312. #ifndef CONFIG_FPU_LAZY
  313.         fpu_context_save(THREAD->saved_fpu_context);
  314. #endif
  315.         if (!context_save(&THREAD->saved_context)) {
  316.             /*
  317.              * This is the place where threads leave scheduler();
  318.              */
  319.             spinlock_unlock(&THREAD->lock);
  320.             interrupts_restore(THREAD->saved_context.ipl);
  321.            
  322.             return;
  323.         }
  324.  
  325.         /*
  326.          * Interrupt priority level of preempted thread is recorded here
  327.          * to facilitate scheduler() invocations from interrupts_disable()'d
  328.          * code (e.g. waitq_sleep_timeout()).
  329.          */
  330.         THREAD->saved_context.ipl = ipl;
  331.     }
  332.  
  333.     /*
  334.      * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM
  335.      * and preemption counter. At this point THE could be coming either
  336.      * from THREAD's or CPU's stack.
  337.      */
  338.     the_copy(THE, (the_t *) CPU->stack);
  339.  
  340.     /*
  341.      * We may not keep the old stack.
  342.      * Reason: If we kept the old stack and got blocked, for instance, in
  343.      * find_best_thread(), the old thread could get rescheduled by another
  344.      * CPU and overwrite the part of its own stack that was also used by
  345.      * the scheduler on this CPU.
  346.      *
  347.      * Moreover, we have to bypass the compiler-generated POP sequence
  348.      * which is fooled by SP being set to the very top of the stack.
  349.      * Therefore the scheduler() function continues in
  350.      * scheduler_separated_stack().
  351.      */
  352.     context_save(&CPU->saved_context);
  353.     context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (__address) CPU->stack, CPU_STACK_SIZE);
  354.     context_restore(&CPU->saved_context);
  355.     /* not reached */
  356. }
  357.  
  358. /** Scheduler stack switch wrapper
  359.  *
  360.  * Second part of the scheduler() function
  361.  * using new stack. Handling the actual context
  362.  * switch to a new thread.
  363.  *
  364.  * Assume THREAD->lock is held.
  365.  */
  366. void scheduler_separated_stack(void)
  367. {
  368.     int priority;
  369.    
  370.     ASSERT(CPU != NULL);
  371.    
  372.     if (THREAD) {
  373.         /* must be run after the switch to scheduler stack */
  374.         after_thread_ran();
  375.  
  376.         switch (THREAD->state) {
  377.             case Running:
  378.             spinlock_unlock(&THREAD->lock);
  379.             thread_ready(THREAD);
  380.             break;
  381.  
  382.             case Exiting:
  383. repeat:
  384.                 if (THREAD->detached) {
  385.                 thread_destroy(THREAD);
  386.             } else {
  387.                 /*
  388.                  * The thread structure is kept allocated until somebody
  389.                  * calls thread_detach() on it.
  390.                  */
  391.                 if (!spinlock_trylock(&THREAD->join_wq.lock)) {
  392.                     /*
  393.                      * Avoid deadlock.
  394.                      */
  395.                     spinlock_unlock(&THREAD->lock);
  396.                     delay(10);
  397.                     spinlock_lock(&THREAD->lock);
  398.                     goto repeat;
  399.                 }
  400.                 _waitq_wakeup_unsafe(&THREAD->join_wq, false);
  401.                 spinlock_unlock(&THREAD->join_wq.lock);
  402.                
  403.                 THREAD->state = Undead;
  404.                 spinlock_unlock(&THREAD->lock);
  405.             }
  406.             break;
  407.            
  408.             case Sleeping:
  409.             /*
  410.              * Prefer the thread after it's woken up.
  411.              */
  412.             THREAD->priority = -1;
  413.  
  414.             /*
  415.              * We need to release wq->lock which we locked in waitq_sleep().
  416.              * Address of wq->lock is kept in THREAD->sleep_queue.
  417.              */
  418.             spinlock_unlock(&THREAD->sleep_queue->lock);
  419.  
  420.             /*
  421.              * Check for possible requests for out-of-context invocation.
  422.              */
  423.             if (THREAD->call_me) {
  424.                 THREAD->call_me(THREAD->call_me_with);
  425.                 THREAD->call_me = NULL;
  426.                 THREAD->call_me_with = NULL;
  427.             }
  428.  
  429.             spinlock_unlock(&THREAD->lock);
  430.  
  431.             break;
  432.  
  433.             default:
  434.             /*
  435.              * Entering state is unexpected.
  436.              */
  437.             panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
  438.             break;
  439.         }
  440.  
  441.         THREAD = NULL;
  442.     }
  443.  
  444.     THREAD = find_best_thread();
  445.    
  446.     spinlock_lock(&THREAD->lock);
  447.     priority = THREAD->priority;
  448.     spinlock_unlock(&THREAD->lock);
  449.  
  450.     relink_rq(priority);       
  451.  
  452.     /*
  453.      * If both the old and the new task are the same, lots of work is avoided.
  454.      */
  455.     if (TASK != THREAD->task) {
  456.         as_t *as1 = NULL;
  457.         as_t *as2;
  458.  
  459.         if (TASK) {
  460.             spinlock_lock(&TASK->lock);
  461.             as1 = TASK->as;
  462.             spinlock_unlock(&TASK->lock);
  463.         }
  464.  
  465.         spinlock_lock(&THREAD->task->lock);
  466.         as2 = THREAD->task->as;
  467.         spinlock_unlock(&THREAD->task->lock);
  468.        
  469.         /*
  470.          * Note that it is possible for two tasks to share one address space.
  471.          */
  472.         if (as1 != as2) {
  473.             /*
  474.              * Both tasks and address spaces are different.
  475.              * Replace the old one with the new one.
  476.              */
  477.             as_switch(as1, as2);
  478.         }
  479.         TASK = THREAD->task;
  480.         before_task_runs();
  481.     }
  482.  
  483.     spinlock_lock(&THREAD->lock);  
  484.     THREAD->state = Running;
  485.  
  486. #ifdef SCHEDULER_VERBOSE
  487.     printf("cpu%d: tid %d (priority=%d,ticks=%lld,nrdy=%ld)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, atomic_get(&CPU->nrdy));
  488. #endif 
  489.  
  490.     /*
  491.      * Some architectures provide late kernel PA2KA(identity)
  492.      * mapping in a page fault handler. However, the page fault
  493.      * handler uses the kernel stack of the running thread and
  494.      * therefore cannot be used to map it. The kernel stack, if
  495.      * necessary, is to be mapped in before_thread_runs(). This
  496.      * function must be executed before the switch to the new stack.
  497.      */
  498.     before_thread_runs();
  499.  
  500.     /*
  501.      * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
  502.      */
  503.     the_copy(THE, (the_t *) THREAD->kstack);
  504.    
  505.     context_restore(&THREAD->saved_context);
  506.     /* not reached */
  507. }
  508.  
  509. #ifdef CONFIG_SMP
  510. /** Load balancing thread
  511.  *
  512.  * SMP load balancing thread, supervising thread supplies
  513.  * for the CPU it's wired to.
  514.  *
  515.  * @param arg Generic thread argument (unused).
  516.  *
  517.  */
  518. void kcpulb(void *arg)
  519. {
  520.     thread_t *t;
  521.     int count, average, i, j, k = 0;
  522.     ipl_t ipl;
  523.  
  524.     /*
  525.      * Detach kcpulb as nobody will call thread_join_timeout() on it.
  526.      */
  527.     thread_detach(THREAD);
  528.    
  529. loop:
  530.     /*
  531.      * Work in 1s intervals.
  532.      */
  533.     thread_sleep(1);
  534.  
  535. not_satisfied:
  536.     /*
  537.      * Calculate the number of threads that will be migrated/stolen from
  538.      * other CPU's. Note that situation can have changed between two
  539.      * passes. Each time get the most up to date counts.
  540.      */
  541.     average = atomic_get(&nrdy) / config.cpu_active + 1;
  542.     count = average - atomic_get(&CPU->nrdy);
  543.  
  544.     if (count <= 0)
  545.         goto satisfied;
  546.  
  547.     /*
  548.      * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
  549.      */
  550.     for (j=RQ_COUNT-1; j >= 0; j--) {
  551.         for (i=0; i < config.cpu_active; i++) {
  552.             link_t *l;
  553.             runq_t *r;
  554.             cpu_t *cpu;
  555.  
  556.             cpu = &cpus[(i + k) % config.cpu_active];
  557.  
  558.             /*
  559.              * Not interested in ourselves.
  560.              * Doesn't require interrupt disabling for kcpulb is X_WIRED.
  561.              */
  562.             if (CPU == cpu)
  563.                 continue;
  564.             if (atomic_get(&cpu->nrdy) <= average)
  565.                 continue;
  566.  
  567.             ipl = interrupts_disable();
  568.             r = &cpu->rq[j];
  569.             spinlock_lock(&r->lock);
  570.             if (r->n == 0) {
  571.                 spinlock_unlock(&r->lock);
  572.                 interrupts_restore(ipl);
  573.                 continue;
  574.             }
  575.        
  576.             t = NULL;
  577.             l = r->rq_head.prev;    /* search rq from the back */
  578.             while (l != &r->rq_head) {
  579.                 t = list_get_instance(l, thread_t, rq_link);
  580.                 /*
  581.                  * We don't want to steal CPU-wired threads neither threads already stolen.
  582.                  * The latter prevents threads from migrating between CPU's without ever being run.
  583.                  * We don't want to steal threads whose FPU context is still in CPU.
  584.                  */
  585.                 spinlock_lock(&t->lock);
  586.                 if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
  587.                     /*
  588.                      * Remove t from r.
  589.                      */
  590.                     spinlock_unlock(&t->lock);
  591.                    
  592.                     atomic_dec(&cpu->nrdy);
  593.                     atomic_dec(&nrdy);
  594.  
  595.                     r->n--;
  596.                     list_remove(&t->rq_link);
  597.  
  598.                     break;
  599.                 }
  600.                 spinlock_unlock(&t->lock);
  601.                 l = l->prev;
  602.                 t = NULL;
  603.             }
  604.             spinlock_unlock(&r->lock);
  605.  
  606.             if (t) {
  607.                 /*
  608.                  * Ready t on local CPU
  609.                  */
  610.                 spinlock_lock(&t->lock);
  611. #ifdef KCPULB_VERBOSE
  612.                 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);
  613. #endif
  614.                 t->flags |= X_STOLEN;
  615.                 t->state = Entering;
  616.                 spinlock_unlock(&t->lock);
  617.    
  618.                 thread_ready(t);
  619.  
  620.                 interrupts_restore(ipl);
  621.    
  622.                 if (--count == 0)
  623.                     goto satisfied;
  624.                    
  625.                 /*
  626.                  * We are not satisfied yet, focus on another CPU next time.
  627.                  */
  628.                 k++;
  629.                
  630.                 continue;
  631.             }
  632.             interrupts_restore(ipl);
  633.         }
  634.     }
  635.  
  636.     if (atomic_get(&CPU->nrdy)) {
  637.         /*
  638.          * Be a little bit light-weight and let migrated threads run.
  639.          */
  640.         scheduler();
  641.     } else {
  642.         /*
  643.          * We failed to migrate a single thread.
  644.          * Give up this turn.
  645.          */
  646.         goto loop;
  647.     }
  648.        
  649.     goto not_satisfied;
  650.  
  651. satisfied:
  652.     goto loop;
  653. }
  654.  
  655. #endif /* CONFIG_SMP */
  656.  
  657.  
  658. /** Print information about threads & scheduler queues */
  659. void sched_print_list(void)
  660. {
  661.     ipl_t ipl;
  662.     int cpu,i;
  663.     runq_t *r;
  664.     thread_t *t;
  665.     link_t *cur;
  666.  
  667.     /* We are going to mess with scheduler structures,
  668.      * let's not be interrupted */
  669.     ipl = interrupts_disable();
  670.     for (cpu=0;cpu < config.cpu_count; cpu++) {
  671.  
  672.         if (!cpus[cpu].active)
  673.             continue;
  674.  
  675.         spinlock_lock(&cpus[cpu].lock);
  676.         printf("cpu%d: address=%p, nrdy=%ld, needs_relink=%ld\n",
  677.                cpus[cpu].id, &cpus[cpu], atomic_get(&cpus[cpu].nrdy), cpus[cpu].needs_relink);
  678.        
  679.         for (i=0; i<RQ_COUNT; i++) {
  680.             r = &cpus[cpu].rq[i];
  681.             spinlock_lock(&r->lock);
  682.             if (!r->n) {
  683.                 spinlock_unlock(&r->lock);
  684.                 continue;
  685.             }
  686.             printf("\trq[%d]: ", i);
  687.             for (cur=r->rq_head.next; cur!=&r->rq_head; cur=cur->next) {
  688.                 t = list_get_instance(cur, thread_t, rq_link);
  689.                 printf("%d(%s) ", t->tid,
  690.                        thread_states[t->state]);
  691.             }
  692.             printf("\n");
  693.             spinlock_unlock(&r->lock);
  694.         }
  695.         spinlock_unlock(&cpus[cpu].lock);
  696.     }
  697.    
  698.     interrupts_restore(ipl);
  699. }
  700.  
  701.  /** @}
  702.  */
  703.  
  704.