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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   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. #include <console/klog.h>
  71.  
  72.  
  73. /** Thread states */
  74. char *thread_states[] = {
  75.     "Invalid",
  76.     "Running",
  77.     "Sleeping",
  78.     "Ready",
  79.     "Entering",
  80.     "Exiting",
  81.     "Lingering"
  82. };
  83.  
  84. /** Lock protecting the threads_btree B+tree.
  85.  *
  86.  * For locking rules, see declaration thereof.
  87.  */
  88. SPINLOCK_INITIALIZE(threads_lock);
  89.  
  90. /** B+tree of all threads.
  91.  *
  92.  * When a thread is found in the threads_btree B+tree, it is guaranteed to
  93.  * exist as long as the threads_lock is held.
  94.  */
  95. btree_t threads_btree;     
  96.  
  97. SPINLOCK_INITIALIZE(tidlock);
  98. thread_id_t last_tid = 0;
  99.  
  100. static slab_cache_t *thread_slab;
  101. #ifdef ARCH_HAS_FPU
  102. slab_cache_t *fpu_context_slab;
  103. #endif
  104.  
  105. /** Thread wrapper.
  106.  *
  107.  * This wrapper is provided to ensure that every thread makes a call to
  108.  * thread_exit() when its implementing function returns.
  109.  *
  110.  * interrupts_disable() is assumed.
  111.  *
  112.  */
  113. static void cushion(void)
  114. {
  115.     void (*f)(void *) = THREAD->thread_code;
  116.     void *arg = THREAD->thread_arg;
  117.     THREAD->last_cycle = get_cycle();
  118.  
  119.     /* This is where each thread wakes up after its creation */
  120.     spinlock_unlock(&THREAD->lock);
  121.     interrupts_enable();
  122.  
  123.     f(arg);
  124.    
  125.     /* Accumulate accounting to the task */
  126.     ipl_t ipl = interrupts_disable();
  127.    
  128.     spinlock_lock(&THREAD->lock);
  129.     if (!THREAD->uncounted) {
  130.         thread_update_accounting();
  131.         uint64_t cycles = THREAD->cycles;
  132.         THREAD->cycles = 0;
  133.         spinlock_unlock(&THREAD->lock);
  134.        
  135.         spinlock_lock(&TASK->lock);
  136.         TASK->cycles += cycles;
  137.         spinlock_unlock(&TASK->lock);
  138.     } else
  139.         spinlock_unlock(&THREAD->lock);
  140.    
  141.     interrupts_restore(ipl);
  142.    
  143.     thread_exit();
  144.     /* not reached */
  145. }
  146.  
  147. /** Initialization and allocation for thread_t structure */
  148. static int thr_constructor(void *obj, int kmflags)
  149. {
  150.     thread_t *t = (thread_t *) obj;
  151.  
  152.     spinlock_initialize(&t->lock, "thread_t_lock");
  153.     link_initialize(&t->rq_link);
  154.     link_initialize(&t->wq_link);
  155.     link_initialize(&t->th_link);
  156.  
  157.     /* call the architecture-specific part of the constructor */
  158.     thr_constructor_arch(t);
  159.    
  160. #ifdef ARCH_HAS_FPU
  161. #ifdef CONFIG_FPU_LAZY
  162.     t->saved_fpu_context = NULL;
  163. #else
  164.     t->saved_fpu_context = slab_alloc(fpu_context_slab, kmflags);
  165.     if (!t->saved_fpu_context)
  166.         return -1;
  167. #endif
  168. #endif 
  169.  
  170.     t->kstack = (uint8_t *) frame_alloc(STACK_FRAMES, FRAME_KA | kmflags);
  171.     if (!t->kstack) {
  172. #ifdef ARCH_HAS_FPU
  173.         if (t->saved_fpu_context)
  174.             slab_free(fpu_context_slab, t->saved_fpu_context);
  175. #endif
  176.         return -1;
  177.     }
  178.  
  179.     return 0;
  180. }
  181.  
  182. /** Destruction of thread_t object */
  183. static int thr_destructor(void *obj)
  184. {
  185.     thread_t *t = (thread_t *) obj;
  186.  
  187.     /* call the architecture-specific part of the destructor */
  188.     thr_destructor_arch(t);
  189.  
  190.     frame_free(KA2PA(t->kstack));
  191. #ifdef ARCH_HAS_FPU
  192.     if (t->saved_fpu_context)
  193.         slab_free(fpu_context_slab, t->saved_fpu_context);
  194. #endif
  195.     return 1; /* One page freed */
  196. }
  197.  
  198. /** Initialize threads
  199.  *
  200.  * Initialize kernel threads support.
  201.  *
  202.  */
  203. void thread_init(void)
  204. {
  205.     THREAD = NULL;
  206.     atomic_set(&nrdy,0);
  207.     thread_slab = slab_cache_create("thread_slab", sizeof(thread_t), 0,
  208.         thr_constructor, thr_destructor, 0);
  209.  
  210. #ifdef ARCH_HAS_FPU
  211.     fpu_context_slab = slab_cache_create("fpu_slab", sizeof(fpu_context_t),
  212.         FPU_CONTEXT_ALIGN, NULL, NULL, 0);
  213. #endif
  214.  
  215.     btree_create(&threads_btree);
  216. }
  217.  
  218. /** Make thread ready
  219.  *
  220.  * Switch thread t to the ready state.
  221.  *
  222.  * @param t Thread to make ready.
  223.  *
  224.  */
  225. void thread_ready(thread_t *t)
  226. {
  227.     cpu_t *cpu;
  228.     runq_t *r;
  229.     ipl_t ipl;
  230.     int i, avg;
  231.  
  232.     ipl = interrupts_disable();
  233.  
  234.     spinlock_lock(&t->lock);
  235.  
  236.     ASSERT(!(t->state == Ready));
  237.  
  238.     i = (t->priority < RQ_COUNT - 1) ? ++t->priority : t->priority;
  239.    
  240.     cpu = CPU;
  241.     if (t->flags & THREAD_FLAG_WIRED) {
  242.         ASSERT(t->cpu != NULL);
  243.         cpu = t->cpu;
  244.     }
  245.     t->state = Ready;
  246.     spinlock_unlock(&t->lock);
  247.    
  248.     /*
  249.      * Append t to respective ready queue on respective processor.
  250.      */
  251.     r = &cpu->rq[i];
  252.     spinlock_lock(&r->lock);
  253.     list_append(&t->rq_link, &r->rq_head);
  254.     r->n++;
  255.     spinlock_unlock(&r->lock);
  256.  
  257.     atomic_inc(&nrdy);
  258.     avg = atomic_get(&nrdy) / config.cpu_active;
  259.     atomic_inc(&cpu->nrdy);
  260.  
  261.     interrupts_restore(ipl);
  262. }
  263.  
  264. /** Create new thread
  265.  *
  266.  * Create a new thread.
  267.  *
  268.  * @param func      Thread's implementing function.
  269.  * @param arg       Thread's implementing function argument.
  270.  * @param task      Task to which the thread belongs.
  271.  * @param flags     Thread flags.
  272.  * @param name      Symbolic name.
  273.  * @param uncounted Thread's accounting doesn't affect accumulated task
  274.  *          accounting.
  275.  *
  276.  * @return New thread's structure on success, NULL on failure.
  277.  *
  278.  */
  279. thread_t *thread_create(void (* func)(void *), void *arg, task_t *task,
  280.     int flags, char *name, bool uncounted)
  281. {
  282.     thread_t *t;
  283.     ipl_t ipl;
  284.    
  285.     t = (thread_t *) slab_alloc(thread_slab, 0);
  286.     if (!t)
  287.         return NULL;
  288.    
  289.     /* Not needed, but good for debugging */
  290.     memsetb((uintptr_t) t->kstack, THREAD_STACK_SIZE * 1 << STACK_FRAMES,
  291.         0);
  292.    
  293.     ipl = interrupts_disable();
  294.     spinlock_lock(&tidlock);
  295.     t->tid = ++last_tid;
  296.     spinlock_unlock(&tidlock);
  297.     interrupts_restore(ipl);
  298.    
  299.     context_save(&t->saved_context);
  300.     context_set(&t->saved_context, FADDR(cushion), (uintptr_t) t->kstack,
  301.         THREAD_STACK_SIZE);
  302.    
  303.     the_initialize((the_t *) t->kstack);
  304.    
  305.     ipl = interrupts_disable();
  306.     t->saved_context.ipl = interrupts_read();
  307.     interrupts_restore(ipl);
  308.    
  309.     memcpy(t->name, name, THREAD_NAME_BUFLEN);
  310.    
  311.     t->thread_code = func;
  312.     t->thread_arg = arg;
  313.     t->ticks = -1;
  314.     t->cycles = 0;
  315.     t->uncounted = uncounted;
  316.     t->priority = -1;       /* start in rq[0] */
  317.     t->cpu = NULL;
  318.     t->flags = flags;
  319.     t->state = Entering;
  320.     t->call_me = NULL;
  321.     t->call_me_with = NULL;
  322.    
  323.     timeout_initialize(&t->sleep_timeout);
  324.     t->sleep_interruptible = false;
  325.     t->sleep_queue = NULL;
  326.     t->timeout_pending = 0;
  327.  
  328.     t->in_copy_from_uspace = false;
  329.     t->in_copy_to_uspace = false;
  330.  
  331.     t->interrupted = false;
  332.     t->detached = false;
  333.     waitq_initialize(&t->join_wq);
  334.    
  335.     t->rwlock_holder_type = RWLOCK_NONE;
  336.        
  337.     t->task = task;
  338.    
  339.     t->fpu_context_exists = 0;
  340.     t->fpu_context_engaged = 0;
  341.  
  342.     /* might depend on previous initialization */
  343.     thread_create_arch(t); 
  344.  
  345.     if (!(flags & THREAD_FLAG_NOATTACH))
  346.         thread_attach(t, task);
  347.  
  348.     return t;
  349. }
  350.  
  351. /** Destroy thread memory structure
  352.  *
  353.  * Detach thread from all queues, cpus etc. and destroy it.
  354.  *
  355.  * Assume thread->lock is held!!
  356.  */
  357. void thread_destroy(thread_t *t)
  358. {
  359.     ASSERT(t->state == Exiting || t->state == Lingering);
  360.     ASSERT(t->task);
  361.     ASSERT(t->cpu);
  362.  
  363.     spinlock_lock(&t->cpu->lock);
  364.     if (t->cpu->fpu_owner == t)
  365.         t->cpu->fpu_owner = NULL;
  366.     spinlock_unlock(&t->cpu->lock);
  367.  
  368.     spinlock_unlock(&t->lock);
  369.  
  370.     spinlock_lock(&threads_lock);
  371.     btree_remove(&threads_btree, (btree_key_t) ((uintptr_t ) t), NULL);
  372.     spinlock_unlock(&threads_lock);
  373.  
  374.     /*
  375.      * Detach from the containing task.
  376.      */
  377.     spinlock_lock(&t->task->lock);
  378.     list_remove(&t->th_link);
  379.     spinlock_unlock(&t->task->lock);   
  380.  
  381.     /*
  382.      * t is guaranteed to be the very last thread of its task.
  383.      * It is safe to destroy the task.
  384.      */
  385.     if (atomic_predec(&t->task->refcount) == 0)
  386.         task_destroy(t->task);
  387.    
  388.     slab_free(thread_slab, t);
  389. }
  390.  
  391. /** Make the thread visible to the system.
  392.  *
  393.  * Attach the thread structure to the current task and make it visible in the
  394.  * threads_btree.
  395.  *
  396.  * @param t Thread to be attached to the task.
  397.  * @param task  Task to which the thread is to be attached.
  398.  */
  399. void thread_attach(thread_t *t, task_t *task)
  400. {
  401.     ipl_t ipl;
  402.  
  403.     /*
  404.      * Attach to the current task.
  405.      */
  406.     ipl = interrupts_disable();
  407.     spinlock_lock(&task->lock);
  408.     atomic_inc(&task->refcount);
  409.     atomic_inc(&task->lifecount);
  410.     list_append(&t->th_link, &task->th_head);
  411.     spinlock_unlock(&task->lock);
  412.  
  413.     /*
  414.      * Register this thread in the system-wide list.
  415.      */
  416.     spinlock_lock(&threads_lock);
  417.     btree_insert(&threads_btree, (btree_key_t) ((uintptr_t) t), (void *) t,
  418.         NULL);
  419.     spinlock_unlock(&threads_lock);
  420.    
  421.     interrupts_restore(ipl);
  422. }
  423.  
  424. /** Terminate thread.
  425.  *
  426.  * End current thread execution and switch it to the exiting state. All pending
  427.  * timeouts are executed.
  428.  */
  429. void thread_exit(void)
  430. {
  431.     ipl_t ipl;
  432.  
  433.     if (atomic_predec(&TASK->lifecount) == 0) {
  434.         /*
  435.          * We are the last thread in the task that still has not exited.
  436.          * With the exception of the moment the task was created, new
  437.          * threads can only be created by threads of the same task.
  438.          * We are safe to perform cleanup.
  439.          */
  440.         if (THREAD->flags & THREAD_FLAG_USPACE) {
  441.             ipc_cleanup();
  442.                 futex_cleanup();
  443.             klog_printf("Cleanup of task %llu completed.",
  444.                 TASK->taskid);
  445.         }
  446.     }
  447.  
  448. restart:
  449.     ipl = interrupts_disable();
  450.     spinlock_lock(&THREAD->lock);
  451.     if (THREAD->timeout_pending) {
  452.         /* busy waiting for timeouts in progress */
  453.         spinlock_unlock(&THREAD->lock);
  454.         interrupts_restore(ipl);
  455.         goto restart;
  456.     }
  457.    
  458.     THREAD->state = Exiting;
  459.     spinlock_unlock(&THREAD->lock);
  460.     scheduler();
  461.  
  462.     /* Not reached */
  463.     while (1)
  464.         ;
  465. }
  466.  
  467.  
  468. /** Thread sleep
  469.  *
  470.  * Suspend execution of the current thread.
  471.  *
  472.  * @param sec Number of seconds to sleep.
  473.  *
  474.  */
  475. void thread_sleep(uint32_t sec)
  476. {
  477.     thread_usleep(sec * 1000000);
  478. }
  479.  
  480. /** Wait for another thread to exit.
  481.  *
  482.  * @param t Thread to join on exit.
  483.  * @param usec Timeout in microseconds.
  484.  * @param flags Mode of operation.
  485.  *
  486.  * @return An error code from errno.h or an error code from synch.h.
  487.  */
  488. int thread_join_timeout(thread_t *t, uint32_t usec, int flags)
  489. {
  490.     ipl_t ipl;
  491.     int rc;
  492.  
  493.     if (t == THREAD)
  494.         return EINVAL;
  495.  
  496.     /*
  497.      * Since thread join can only be called once on an undetached thread,
  498.      * the thread pointer is guaranteed to be still valid.
  499.      */
  500.    
  501.     ipl = interrupts_disable();
  502.     spinlock_lock(&t->lock);
  503.     ASSERT(!t->detached);
  504.     spinlock_unlock(&t->lock);
  505.     interrupts_restore(ipl);
  506.    
  507.     rc = waitq_sleep_timeout(&t->join_wq, usec, flags);
  508.    
  509.     return rc; 
  510. }
  511.  
  512. /** Detach thread.
  513.  *
  514.  * Mark the thread as detached, if the thread is already in the Lingering
  515.  * state, deallocate its resources.
  516.  *
  517.  * @param t Thread to be detached.
  518.  */
  519. void thread_detach(thread_t *t)
  520. {
  521.     ipl_t ipl;
  522.  
  523.     /*
  524.      * Since the thread is expected not to be already detached,
  525.      * pointer to it must be still valid.
  526.      */
  527.     ipl = interrupts_disable();
  528.     spinlock_lock(&t->lock);
  529.     ASSERT(!t->detached);
  530.     if (t->state == Lingering) {
  531.         thread_destroy(t);  /* unlocks &t->lock */
  532.         interrupts_restore(ipl);
  533.         return;
  534.     } else {
  535.         t->detached = true;
  536.     }
  537.     spinlock_unlock(&t->lock);
  538.     interrupts_restore(ipl);
  539. }
  540.  
  541. /** Thread usleep
  542.  *
  543.  * Suspend execution of the current thread.
  544.  *
  545.  * @param usec Number of microseconds to sleep.
  546.  *
  547.  */
  548. void thread_usleep(uint32_t usec)
  549. {
  550.     waitq_t wq;
  551.                  
  552.     waitq_initialize(&wq);
  553.  
  554.     (void) waitq_sleep_timeout(&wq, usec, SYNCH_FLAGS_NON_BLOCKING);
  555. }
  556.  
  557. /** Register thread out-of-context invocation
  558.  *
  559.  * Register a function and its argument to be executed
  560.  * on next context switch to the current thread.
  561.  *
  562.  * @param call_me      Out-of-context function.
  563.  * @param call_me_with Out-of-context function argument.
  564.  *
  565.  */
  566. void thread_register_call_me(void (* call_me)(void *), void *call_me_with)
  567. {
  568.     ipl_t ipl;
  569.    
  570.     ipl = interrupts_disable();
  571.     spinlock_lock(&THREAD->lock);
  572.     THREAD->call_me = call_me;
  573.     THREAD->call_me_with = call_me_with;
  574.     spinlock_unlock(&THREAD->lock);
  575.     interrupts_restore(ipl);
  576. }
  577.  
  578. /** Print list of threads debug info */
  579. void thread_print_list(void)
  580. {
  581.     link_t *cur;
  582.     ipl_t ipl;
  583.    
  584.     /* Messing with thread structures, avoid deadlock */
  585.     ipl = interrupts_disable();
  586.     spinlock_lock(&threads_lock);
  587.    
  588.     printf("tid    name       address    state    task       ctx code    "
  589.         "   stack      cycles     cpu  kstack     waitqueue\n");
  590.     printf("------ ---------- ---------- -------- ---------- --- --------"
  591.         "-- ---------- ---------- ---- ---------- ----------\n");
  592.  
  593.     for (cur = threads_btree.leaf_head.next;
  594.         cur != &threads_btree.leaf_head; cur = cur->next) {
  595.         btree_node_t *node;
  596.         unsigned int i;
  597.  
  598.         node = list_get_instance(cur, btree_node_t, leaf_link);
  599.         for (i = 0; i < node->keys; i++) {
  600.             thread_t *t;
  601.        
  602.             t = (thread_t *) node->value[i];
  603.            
  604.             uint64_t cycles;
  605.             char suffix;
  606.             order(t->cycles, &cycles, &suffix);
  607.            
  608.             printf("%-6llu %-10s %#10zx %-8s %#10zx %-3ld %#10zx "
  609.                 "%#10zx %9llu%c ", t->tid, t->name, t,
  610.                 thread_states[t->state], t->task, t->task->context,
  611.                 t->thread_code, t->kstack, cycles, suffix);
  612.            
  613.             if (t->cpu)
  614.                 printf("%-4zd", t->cpu->id);
  615.             else
  616.                 printf("none");
  617.            
  618.             if (t->state == Sleeping)
  619.                 printf(" %#10zx %#10zx", t->kstack,
  620.                     t->sleep_queue);
  621.            
  622.             printf("\n");
  623.         }
  624.     }
  625.  
  626.     spinlock_unlock(&threads_lock);
  627.     interrupts_restore(ipl);
  628. }
  629.  
  630. /** Check whether thread exists.
  631.  *
  632.  * Note that threads_lock must be already held and
  633.  * interrupts must be already disabled.
  634.  *
  635.  * @param t Pointer to thread.
  636.  *
  637.  * @return True if thread t is known to the system, false otherwise.
  638.  */
  639. bool thread_exists(thread_t *t)
  640. {
  641.     btree_node_t *leaf;
  642.    
  643.     return btree_search(&threads_btree, (btree_key_t) ((uintptr_t) t),
  644.         &leaf) != NULL;
  645. }
  646.  
  647.  
  648. /** Update accounting of current thread.
  649.  *
  650.  * Note that thread_lock on THREAD must be already held and
  651.  * interrupts must be already disabled.
  652.  *
  653.  */
  654. void thread_update_accounting(void)
  655. {
  656.     uint64_t time = get_cycle();
  657.     THREAD->cycles += time - THREAD->last_cycle;
  658.     THREAD->last_cycle = time;
  659. }
  660.  
  661. /** Process syscall to create new thread.
  662.  *
  663.  */
  664. unative_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
  665.     thread_id_t *uspace_thread_id)
  666. {
  667.     thread_t *t;
  668.     char namebuf[THREAD_NAME_BUFLEN];
  669.     uspace_arg_t *kernel_uarg;
  670.     int rc;
  671.  
  672.     rc = copy_from_uspace(namebuf, uspace_name, THREAD_NAME_BUFLEN);
  673.     if (rc != 0)
  674.         return (unative_t) rc;
  675.  
  676.     /*
  677.      * In case of failure, kernel_uarg will be deallocated in this function.
  678.      * In case of success, kernel_uarg will be freed in uinit().
  679.      */
  680.     kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
  681.    
  682.     rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
  683.     if (rc != 0) {
  684.         free(kernel_uarg);
  685.         return (unative_t) rc;
  686.     }
  687.  
  688.     t = thread_create(uinit, kernel_uarg, TASK,
  689.         THREAD_FLAG_USPACE | THREAD_FLAG_NOATTACH, namebuf, false);
  690.     if (t) {
  691.         if (uspace_thread_id != NULL) {
  692.             int rc;
  693.  
  694.             rc = copy_to_uspace(uspace_thread_id, &t->tid,
  695.                 sizeof(t->tid));
  696.             if (rc != 0) {
  697.                 /*
  698.                  * We have encountered a failure, but the thread
  699.                  * has already been created. We need to undo its
  700.                  * creation now.
  701.                  */
  702.  
  703.                 /*
  704.                  * The new thread structure is initialized, but
  705.                  * is still not visible to the system.
  706.                  * We can safely deallocate it.
  707.                  */
  708.                 slab_free(thread_slab, t);
  709.                 free(kernel_uarg);
  710.  
  711.                 return (unative_t) rc;
  712.              }
  713.         }
  714.         thread_attach(t, TASK);
  715.         thread_ready(t);
  716.  
  717.         return 0;
  718.     } else
  719.         free(kernel_uarg);
  720.  
  721.     return (unative_t) ENOMEM;
  722. }
  723.  
  724. /** Process syscall to terminate thread.
  725.  *
  726.  */
  727. unative_t sys_thread_exit(int uspace_status)
  728. {
  729.     thread_exit();
  730.     /* Unreachable */
  731.     return 0;
  732. }
  733.  
  734. /** Syscall for getting TID.
  735.  *
  736.  * @param uspace_thread_id Userspace address of 8-byte buffer where to store
  737.  * current thread ID.
  738.  *
  739.  * @return 0 on success or an error code from @ref errno.h.
  740.  */
  741. unative_t sys_thread_get_id(thread_id_t *uspace_thread_id)
  742. {
  743.     /*
  744.      * No need to acquire lock on THREAD because tid
  745.      * remains constant for the lifespan of the thread.
  746.      */
  747.     return (unative_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
  748.         sizeof(THREAD->tid));
  749. }
  750.  
  751. /** @}
  752.  */
  753.