Subversion Repositories HelenOS

Rev

Rev 2216 | Rev 2268 | Go to most recent revision | Blame | Compare with Previous | Last modification | View Log | Download | RSS feed

  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   Thread management functions.
  36.  */
  37.  
  38. #include <proc/scheduler.h>
  39. #include <proc/thread.h>
  40. #include <proc/task.h>
  41. #include <proc/uarg.h>
  42. #include <mm/frame.h>
  43. #include <mm/page.h>
  44. #include <arch/asm.h>
  45. #include <arch/cycle.h>
  46. #include <arch.h>
  47. #include <synch/synch.h>
  48. #include <synch/spinlock.h>
  49. #include <synch/waitq.h>
  50. #include <synch/rwlock.h>
  51. #include <cpu.h>
  52. #include <func.h>
  53. #include <context.h>
  54. #include <adt/btree.h>
  55. #include <adt/list.h>
  56. #include <time/clock.h>
  57. #include <time/timeout.h>
  58. #include <config.h>
  59. #include <arch/interrupt.h>
  60. #include <smp/ipi.h>
  61. #include <arch/faddr.h>
  62. #include <atomic.h>
  63. #include <memstr.h>
  64. #include <print.h>
  65. #include <mm/slab.h>
  66. #include <debug.h>
  67. #include <main/uinit.h>
  68. #include <syscall/copy.h>
  69. #include <errno.h>
  70.  
  71.  
  72. /** Thread states */
  73. char *thread_states[] = {
  74.     "Invalid",
  75.     "Running",
  76.     "Sleeping",
  77.     "Ready",
  78.     "Entering",
  79.     "Exiting",
  80.     "Undead"
  81. };
  82.  
  83. /** Lock protecting the threads_btree B+tree.
  84.  *
  85.  * For locking rules, see declaration thereof.
  86.  */
  87. SPINLOCK_INITIALIZE(threads_lock);
  88.  
  89. /** B+tree of all threads.
  90.  *
  91.  * When a thread is found in the threads_btree B+tree, it is guaranteed to
  92.  * exist as long as the threads_lock is held.
  93.  */
  94. btree_t threads_btree;     
  95.  
  96. SPINLOCK_INITIALIZE(tidlock);
  97. thread_id_t last_tid = 0;
  98.  
  99. static slab_cache_t *thread_slab;
  100. #ifdef ARCH_HAS_FPU
  101. slab_cache_t *fpu_context_slab;
  102. #endif
  103.  
  104. /** Thread wrapper.
  105.  *
  106.  * This wrapper is provided to ensure that every thread makes a call to
  107.  * thread_exit() when its implementing function returns.
  108.  *
  109.  * interrupts_disable() is assumed.
  110.  *
  111.  */
  112. static void cushion(void)
  113. {
  114.     void (*f)(void *) = THREAD->thread_code;
  115.     void *arg = THREAD->thread_arg;
  116.     THREAD->last_cycle = get_cycle();
  117.  
  118.     /* This is where each thread wakes up after its creation */
  119.     spinlock_unlock(&THREAD->lock);
  120.     interrupts_enable();
  121.  
  122.     f(arg);
  123.    
  124.     /* Accumulate accounting to the task */
  125.     ipl_t ipl = interrupts_disable();
  126.    
  127.     spinlock_lock(&THREAD->lock);
  128.     if (!THREAD->uncounted) {
  129.         thread_update_accounting();
  130.         uint64_t cycles = THREAD->cycles;
  131.         THREAD->cycles = 0;
  132.         spinlock_unlock(&THREAD->lock);
  133.        
  134.         spinlock_lock(&TASK->lock);
  135.         TASK->cycles += cycles;
  136.         spinlock_unlock(&TASK->lock);
  137.     } else
  138.         spinlock_unlock(&THREAD->lock);
  139.    
  140.     interrupts_restore(ipl);
  141.    
  142.     thread_exit();
  143.     /* not reached */
  144. }
  145.  
  146. /** Initialization and allocation for thread_t structure */
  147. static int thr_constructor(void *obj, int kmflags)
  148. {
  149.     thread_t *t = (thread_t *) obj;
  150.  
  151.     spinlock_initialize(&t->lock, "thread_t_lock");
  152.     link_initialize(&t->rq_link);
  153.     link_initialize(&t->wq_link);
  154.     link_initialize(&t->th_link);
  155.  
  156.     /* call the architecture-specific part of the constructor */
  157.     thr_constructor_arch(t);
  158.    
  159. #ifdef ARCH_HAS_FPU
  160. #  ifdef CONFIG_FPU_LAZY
  161.     t->saved_fpu_context = NULL;
  162. #  else
  163.     t->saved_fpu_context = slab_alloc(fpu_context_slab,kmflags);
  164.     if (!t->saved_fpu_context)
  165.         return -1;
  166. #  endif
  167. #endif 
  168.  
  169.     t->kstack = (uint8_t *) frame_alloc(STACK_FRAMES, FRAME_KA | kmflags);
  170.     if (! t->kstack) {
  171. #ifdef ARCH_HAS_FPU
  172.         if (t->saved_fpu_context)
  173.             slab_free(fpu_context_slab,t->saved_fpu_context);
  174. #endif
  175.         return -1;
  176.     }
  177.  
  178.     return 0;
  179. }
  180.  
  181. /** Destruction of thread_t object */
  182. static int thr_destructor(void *obj)
  183. {
  184.     thread_t *t = (thread_t *) obj;
  185.  
  186.     /* call the architecture-specific part of the destructor */
  187.     thr_destructor_arch(t);
  188.  
  189.     frame_free(KA2PA(t->kstack));
  190. #ifdef ARCH_HAS_FPU
  191.     if (t->saved_fpu_context)
  192.         slab_free(fpu_context_slab,t->saved_fpu_context);
  193. #endif
  194.     return 1; /* One page freed */
  195. }
  196.  
  197. /** Initialize threads
  198.  *
  199.  * Initialize kernel threads support.
  200.  *
  201.  */
  202. void thread_init(void)
  203. {
  204.     THREAD = NULL;
  205.     atomic_set(&nrdy,0);
  206.     thread_slab = slab_cache_create("thread_slab", sizeof(thread_t), 0,
  207.         thr_constructor, thr_destructor, 0);
  208.  
  209. #ifdef ARCH_HAS_FPU
  210.     fpu_context_slab = slab_cache_create("fpu_slab", sizeof(fpu_context_t),
  211.         FPU_CONTEXT_ALIGN, NULL, NULL, 0);
  212. #endif
  213.  
  214.     btree_create(&threads_btree);
  215. }
  216.  
  217. /** Make thread ready
  218.  *
  219.  * Switch thread t to the ready state.
  220.  *
  221.  * @param t Thread to make ready.
  222.  *
  223.  */
  224. void thread_ready(thread_t *t)
  225. {
  226.     cpu_t *cpu;
  227.     runq_t *r;
  228.     ipl_t ipl;
  229.     int i, avg;
  230.  
  231.     ipl = interrupts_disable();
  232.  
  233.     spinlock_lock(&t->lock);
  234.  
  235.     ASSERT(! (t->state == Ready));
  236.  
  237.     i = (t->priority < RQ_COUNT - 1) ? ++t->priority : t->priority;
  238.    
  239.     cpu = CPU;
  240.     if (t->flags & THREAD_FLAG_WIRED) {
  241.         cpu = t->cpu;
  242.     }
  243.     t->state = Ready;
  244.     spinlock_unlock(&t->lock);
  245.    
  246.     /*
  247.      * Append t to respective ready queue on respective processor.
  248.      */
  249.     r = &cpu->rq[i];
  250.     spinlock_lock(&r->lock);
  251.     list_append(&t->rq_link, &r->rq_head);
  252.     r->n++;
  253.     spinlock_unlock(&r->lock);
  254.  
  255.     atomic_inc(&nrdy);
  256.     avg = atomic_get(&nrdy) / config.cpu_active;
  257.     atomic_inc(&cpu->nrdy);
  258.  
  259.     interrupts_restore(ipl);
  260. }
  261.  
  262. /** Destroy thread memory structure
  263.  *
  264.  * Detach thread from all queues, cpus etc. and destroy it.
  265.  *
  266.  * Assume thread->lock is held!!
  267.  */
  268. void thread_destroy(thread_t *t)
  269. {
  270.     bool destroy_task = false;
  271.  
  272.     ASSERT(t->state == Exiting || t->state == Undead);
  273.     ASSERT(t->task);
  274.     ASSERT(t->cpu);
  275.  
  276.     spinlock_lock(&t->cpu->lock);
  277.     if(t->cpu->fpu_owner == t)
  278.         t->cpu->fpu_owner = NULL;
  279.     spinlock_unlock(&t->cpu->lock);
  280.  
  281.     spinlock_unlock(&t->lock);
  282.  
  283.     spinlock_lock(&threads_lock);
  284.     btree_remove(&threads_btree, (btree_key_t) ((uintptr_t ) t), NULL);
  285.     spinlock_unlock(&threads_lock);
  286.  
  287.     /*
  288.      * Detach from the containing task.
  289.      */
  290.     spinlock_lock(&t->task->lock);
  291.     list_remove(&t->th_link);
  292.     if (--t->task->refcount == 0) {
  293.         t->task->accept_new_threads = false;
  294.         destroy_task = true;
  295.     }
  296.     spinlock_unlock(&t->task->lock);   
  297.    
  298.     if (destroy_task)
  299.         task_destroy(t->task);
  300.    
  301.     slab_free(thread_slab, t);
  302. }
  303.  
  304. /** Create new thread
  305.  *
  306.  * Create a new thread.
  307.  *
  308.  * @param func      Thread's implementing function.
  309.  * @param arg       Thread's implementing function argument.
  310.  * @param task      Task to which the thread belongs.
  311.  * @param flags     Thread flags.
  312.  * @param name      Symbolic name.
  313.  * @param uncounted Thread's accounting doesn't affect accumulated task
  314.  *   accounting.
  315.  *
  316.  * @return New thread's structure on success, NULL on failure.
  317.  *
  318.  */
  319. thread_t *thread_create(void (* func)(void *), void *arg, task_t *task,
  320.     int flags, char *name, bool uncounted)
  321. {
  322.     thread_t *t;
  323.     ipl_t ipl;
  324.    
  325.     t = (thread_t *) slab_alloc(thread_slab, 0);
  326.     if (!t)
  327.         return NULL;
  328.    
  329.     /* Not needed, but good for debugging */
  330.     memsetb((uintptr_t) t->kstack, THREAD_STACK_SIZE * 1 << STACK_FRAMES,
  331.         0);
  332.    
  333.     ipl = interrupts_disable();
  334.     spinlock_lock(&tidlock);
  335.     t->tid = ++last_tid;
  336.     spinlock_unlock(&tidlock);
  337.     interrupts_restore(ipl);
  338.    
  339.     context_save(&t->saved_context);
  340.     context_set(&t->saved_context, FADDR(cushion), (uintptr_t) t->kstack,
  341.         THREAD_STACK_SIZE);
  342.    
  343.     the_initialize((the_t *) t->kstack);
  344.    
  345.     ipl = interrupts_disable();
  346.     t->saved_context.ipl = interrupts_read();
  347.     interrupts_restore(ipl);
  348.    
  349.     memcpy(t->name, name, THREAD_NAME_BUFLEN);
  350.    
  351.     t->thread_code = func;
  352.     t->thread_arg = arg;
  353.     t->ticks = -1;
  354.     t->cycles = 0;
  355.     t->uncounted = uncounted;
  356.     t->priority = -1;       /* start in rq[0] */
  357.     t->cpu = NULL;
  358.     t->flags = flags;
  359.     t->state = Entering;
  360.     t->call_me = NULL;
  361.     t->call_me_with = NULL;
  362.    
  363.     timeout_initialize(&t->sleep_timeout);
  364.     t->sleep_interruptible = false;
  365.     t->sleep_queue = NULL;
  366.     t->timeout_pending = 0;
  367.  
  368.     t->in_copy_from_uspace = false;
  369.     t->in_copy_to_uspace = false;
  370.  
  371.     t->interrupted = false;
  372.     t->join_type = None;
  373.     t->detached = false;
  374.     waitq_initialize(&t->join_wq);
  375.    
  376.     t->rwlock_holder_type = RWLOCK_NONE;
  377.        
  378.     t->task = task;
  379.    
  380.     t->fpu_context_exists = 0;
  381.     t->fpu_context_engaged = 0;
  382.  
  383.     /* might depend on previous initialization */
  384.     thread_create_arch(t); 
  385.    
  386.     /*
  387.      * Attach to the containing task.
  388.      */
  389.     ipl = interrupts_disable();  
  390.     spinlock_lock(&task->lock);
  391.     if (!task->accept_new_threads) {
  392.         spinlock_unlock(&task->lock);
  393.         slab_free(thread_slab, t);
  394.         interrupts_restore(ipl);
  395.         return NULL;
  396.     }
  397.     list_append(&t->th_link, &task->th_head);
  398.     if (task->refcount++ == 0)
  399.         task->main_thread = t;
  400.     spinlock_unlock(&task->lock);
  401.  
  402.     /*
  403.      * Register this thread in the system-wide list.
  404.      */
  405.     spinlock_lock(&threads_lock);
  406.     btree_insert(&threads_btree, (btree_key_t) ((uintptr_t) t), (void *) t,
  407.         NULL);
  408.     spinlock_unlock(&threads_lock);
  409.    
  410.     interrupts_restore(ipl);
  411.    
  412.     return t;
  413. }
  414.  
  415. /** Terminate thread.
  416.  *
  417.  * End current thread execution and switch it to the exiting state. All pending
  418.  * timeouts are executed.
  419.  */
  420. void thread_exit(void)
  421. {
  422.     ipl_t ipl;
  423.  
  424. restart:
  425.     ipl = interrupts_disable();
  426.     spinlock_lock(&THREAD->lock);
  427.     if (THREAD->timeout_pending) {
  428.         /* busy waiting for timeouts in progress */
  429.         spinlock_unlock(&THREAD->lock);
  430.         interrupts_restore(ipl);
  431.         goto restart;
  432.     }
  433.     THREAD->state = Exiting;
  434.     spinlock_unlock(&THREAD->lock);
  435.     scheduler();
  436.  
  437.     /* Not reached */
  438.     while (1)
  439.         ;
  440. }
  441.  
  442.  
  443. /** Thread sleep
  444.  *
  445.  * Suspend execution of the current thread.
  446.  *
  447.  * @param sec Number of seconds to sleep.
  448.  *
  449.  */
  450. void thread_sleep(uint32_t sec)
  451. {
  452.     thread_usleep(sec * 1000000);
  453. }
  454.  
  455. /** Wait for another thread to exit.
  456.  *
  457.  * @param t Thread to join on exit.
  458.  * @param usec Timeout in microseconds.
  459.  * @param flags Mode of operation.
  460.  *
  461.  * @return An error code from errno.h or an error code from synch.h.
  462.  */
  463. int thread_join_timeout(thread_t *t, uint32_t usec, int flags)
  464. {
  465.     ipl_t ipl;
  466.     int rc;
  467.  
  468.     if (t == THREAD)
  469.         return EINVAL;
  470.  
  471.     /*
  472.      * Since thread join can only be called once on an undetached thread,
  473.      * the thread pointer is guaranteed to be still valid.
  474.      */
  475.    
  476.     ipl = interrupts_disable();
  477.     spinlock_lock(&t->lock);
  478.     ASSERT(!t->detached);
  479.     spinlock_unlock(&t->lock);
  480.     interrupts_restore(ipl);
  481.    
  482.     rc = waitq_sleep_timeout(&t->join_wq, usec, flags);
  483.    
  484.     return rc; 
  485. }
  486.  
  487. /** Detach thread.
  488.  *
  489.  * Mark the thread as detached, if the thread is already in the Undead state,
  490.  * deallocate its resources.
  491.  *
  492.  * @param t Thread to be detached.
  493.  */
  494. void thread_detach(thread_t *t)
  495. {
  496.     ipl_t ipl;
  497.  
  498.     /*
  499.      * Since the thread is expected not to be already detached,
  500.      * pointer to it must be still valid.
  501.      */
  502.     ipl = interrupts_disable();
  503.     spinlock_lock(&t->lock);
  504.     ASSERT(!t->detached);
  505.     if (t->state == Undead) {
  506.         thread_destroy(t);  /* unlocks &t->lock */
  507.         interrupts_restore(ipl);
  508.         return;
  509.     } else {
  510.         t->detached = true;
  511.     }
  512.     spinlock_unlock(&t->lock);
  513.     interrupts_restore(ipl);
  514. }
  515.  
  516. /** Thread usleep
  517.  *
  518.  * Suspend execution of the current thread.
  519.  *
  520.  * @param usec Number of microseconds to sleep.
  521.  *
  522.  */
  523. void thread_usleep(uint32_t usec)
  524. {
  525.     waitq_t wq;
  526.                  
  527.     waitq_initialize(&wq);
  528.  
  529.     (void) waitq_sleep_timeout(&wq, usec, SYNCH_FLAGS_NON_BLOCKING);
  530. }
  531.  
  532. /** Register thread out-of-context invocation
  533.  *
  534.  * Register a function and its argument to be executed
  535.  * on next context switch to the current thread.
  536.  *
  537.  * @param call_me      Out-of-context function.
  538.  * @param call_me_with Out-of-context function argument.
  539.  *
  540.  */
  541. void thread_register_call_me(void (* call_me)(void *), void *call_me_with)
  542. {
  543.     ipl_t ipl;
  544.    
  545.     ipl = interrupts_disable();
  546.     spinlock_lock(&THREAD->lock);
  547.     THREAD->call_me = call_me;
  548.     THREAD->call_me_with = call_me_with;
  549.     spinlock_unlock(&THREAD->lock);
  550.     interrupts_restore(ipl);
  551. }
  552.  
  553. /** Print list of threads debug info */
  554. void thread_print_list(void)
  555. {
  556.     link_t *cur;
  557.     ipl_t ipl;
  558.    
  559.     /* Messing with thread structures, avoid deadlock */
  560.     ipl = interrupts_disable();
  561.     spinlock_lock(&threads_lock);
  562.    
  563.     printf("tid    name       address    state    task       ctx code    "
  564.         "   stack      cycles     cpu  kstack     waitqueue\n");
  565.     printf("------ ---------- ---------- -------- ---------- --- --------"
  566.         "-- ---------- ---------- ---- ---------- ----------\n");
  567.  
  568.     for (cur = threads_btree.leaf_head.next;
  569.         cur != &threads_btree.leaf_head; cur = cur->next) {
  570.         btree_node_t *node;
  571.         unsigned int i;
  572.  
  573.         node = list_get_instance(cur, btree_node_t, leaf_link);
  574.         for (i = 0; i < node->keys; i++) {
  575.             thread_t *t;
  576.        
  577.             t = (thread_t *) node->value[i];
  578.            
  579.             uint64_t cycles;
  580.             char suffix;
  581.             order(t->cycles, &cycles, &suffix);
  582.            
  583.             printf("%-6llu %-10s %#10zx %-8s %#10zx %-3ld %#10zx "
  584.                 "%#10zx %9llu%c ", t->tid, t->name, t,
  585.                 thread_states[t->state], t->task, t->task->context,
  586.                 t->thread_code, t->kstack, cycles, suffix);
  587.            
  588.             if (t->cpu)
  589.                 printf("%-4zd", t->cpu->id);
  590.             else
  591.                 printf("none");
  592.            
  593.             if (t->state == Sleeping)
  594.                 printf(" %#10zx %#10zx", t->kstack,
  595.                     t->sleep_queue);
  596.            
  597.             printf("\n");
  598.         }
  599.     }
  600.  
  601.     spinlock_unlock(&threads_lock);
  602.     interrupts_restore(ipl);
  603. }
  604.  
  605. /** Check whether thread exists.
  606.  *
  607.  * Note that threads_lock must be already held and
  608.  * interrupts must be already disabled.
  609.  *
  610.  * @param t Pointer to thread.
  611.  *
  612.  * @return True if thread t is known to the system, false otherwise.
  613.  */
  614. bool thread_exists(thread_t *t)
  615. {
  616.     btree_node_t *leaf;
  617.    
  618.     return btree_search(&threads_btree, (btree_key_t) ((uintptr_t) t),
  619.         &leaf) != NULL;
  620. }
  621.  
  622.  
  623. /** Update accounting of current thread.
  624.  *
  625.  * Note that thread_lock on THREAD must be already held and
  626.  * interrupts must be already disabled.
  627.  *
  628.  */
  629. void thread_update_accounting(void)
  630. {
  631.     uint64_t time = get_cycle();
  632.     THREAD->cycles += time - THREAD->last_cycle;
  633.     THREAD->last_cycle = time;
  634. }
  635.  
  636. /** Process syscall to create new thread.
  637.  *
  638.  */
  639. unative_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name, thread_id_t *uspace_thread_id)
  640. {
  641.     thread_t *t;
  642.     char namebuf[THREAD_NAME_BUFLEN];
  643.     uspace_arg_t *kernel_uarg;
  644.     int rc;
  645.  
  646.     rc = copy_from_uspace(namebuf, uspace_name, THREAD_NAME_BUFLEN);
  647.     if (rc != 0)
  648.         return (unative_t) rc;
  649.  
  650.     kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
  651.     rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
  652.     if (rc != 0) {
  653.         free(kernel_uarg);
  654.         return (unative_t) rc;
  655.     }
  656.  
  657.     t = thread_create(uinit, kernel_uarg, TASK, THREAD_FLAG_USPACE, namebuf,
  658.         false);
  659.     if (t) {
  660.         thread_ready(t);
  661.         if (uspace_thread_id != NULL)
  662.             return (unative_t) copy_to_uspace(uspace_thread_id, &t->tid,
  663.                 sizeof(t->tid));
  664.         else
  665.             return 0;
  666.     } else
  667.         free(kernel_uarg);
  668.  
  669.     return (unative_t) ENOMEM;
  670. }
  671.  
  672. /** Process syscall to terminate thread.
  673.  *
  674.  */
  675. unative_t sys_thread_exit(int uspace_status)
  676. {
  677.     thread_exit();
  678.     /* Unreachable */
  679.     return 0;
  680. }
  681.  
  682. /** Syscall for getting TID.
  683.  *
  684.  * @param uspace_thread_id Userspace address of 8-byte buffer where to store
  685.  * current thread ID.
  686.  *
  687.  * @return 0 on success or an error code from @ref errno.h.
  688.  */
  689. unative_t sys_thread_get_id(thread_id_t *uspace_thread_id)
  690. {
  691.     /*
  692.      * No need to acquire lock on THREAD because tid
  693.      * remains constant for the lifespan of the thread.
  694.      */
  695.     return (unative_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
  696.         sizeof(THREAD->tid));
  697. }
  698.  
  699. /** @}
  700.  */
  701.