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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/avl.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_tree AVL tree.
  85.  *
  86.  * For locking rules, see declaration thereof.
  87.  */
  88. SPINLOCK_INITIALIZE(threads_lock);
  89.  
  90. /** ALV tree of all threads.
  91.  *
  92.  * When a thread is found in the threads_tree AVL tree, it is guaranteed to
  93.  * exist as long as the threads_lock is held.
  94.  */
  95. avltree_t threads_tree;    
  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.     avltree_create(&threads_tree);
  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.     avltree_node_initialize(&t->threads_tree_node);
  343.     t->threads_tree_node.key = (uintptr_t) t;
  344.  
  345.     /* might depend on previous initialization */
  346.     thread_create_arch(t); 
  347.  
  348.     if (!(flags & THREAD_FLAG_NOATTACH))
  349.         thread_attach(t, task);
  350.  
  351.     return t;
  352. }
  353.  
  354. /** Destroy thread memory structure
  355.  *
  356.  * Detach thread from all queues, cpus etc. and destroy it.
  357.  *
  358.  * Assume thread->lock is held!!
  359.  */
  360. void thread_destroy(thread_t *t)
  361. {
  362.     ASSERT(t->state == Exiting || t->state == Lingering);
  363.     ASSERT(t->task);
  364.     ASSERT(t->cpu);
  365.  
  366.     spinlock_lock(&t->cpu->lock);
  367.     if (t->cpu->fpu_owner == t)
  368.         t->cpu->fpu_owner = NULL;
  369.     spinlock_unlock(&t->cpu->lock);
  370.  
  371.     spinlock_unlock(&t->lock);
  372.  
  373.     spinlock_lock(&threads_lock);
  374.     avltree_delete(&threads_tree, &t->threads_tree_node);
  375.     spinlock_unlock(&threads_lock);
  376.  
  377.     /*
  378.      * Detach from the containing task.
  379.      */
  380.     spinlock_lock(&t->task->lock);
  381.     list_remove(&t->th_link);
  382.     spinlock_unlock(&t->task->lock);   
  383.  
  384.     /*
  385.      * t is guaranteed to be the very last thread of its task.
  386.      * It is safe to destroy the task.
  387.      */
  388.     if (atomic_predec(&t->task->refcount) == 0)
  389.         task_destroy(t->task);
  390.    
  391.     slab_free(thread_slab, t);
  392. }
  393.  
  394. /** Make the thread visible to the system.
  395.  *
  396.  * Attach the thread structure to the current task and make it visible in the
  397.  * threads_tree.
  398.  *
  399.  * @param t Thread to be attached to the task.
  400.  * @param task  Task to which the thread is to be attached.
  401.  */
  402. void thread_attach(thread_t *t, task_t *task)
  403. {
  404.     ipl_t ipl;
  405.  
  406.     /*
  407.      * Attach to the current task.
  408.      */
  409.     ipl = interrupts_disable();
  410.     spinlock_lock(&task->lock);
  411.     atomic_inc(&task->refcount);
  412.     atomic_inc(&task->lifecount);
  413.     list_append(&t->th_link, &task->th_head);
  414.     spinlock_unlock(&task->lock);
  415.  
  416.     /*
  417.      * Register this thread in the system-wide list.
  418.      */
  419.     spinlock_lock(&threads_lock);
  420.     avltree_insert(&threads_tree, &t->threads_tree_node);
  421.     spinlock_unlock(&threads_lock);
  422.    
  423.     interrupts_restore(ipl);
  424. }
  425.  
  426. /** Terminate thread.
  427.  *
  428.  * End current thread execution and switch it to the exiting state. All pending
  429.  * timeouts are executed.
  430.  */
  431. void thread_exit(void)
  432. {
  433.     ipl_t ipl;
  434.  
  435.     if (atomic_predec(&TASK->lifecount) == 0) {
  436.         /*
  437.          * We are the last thread in the task that still has not exited.
  438.          * With the exception of the moment the task was created, new
  439.          * threads can only be created by threads of the same task.
  440.          * We are safe to perform cleanup.
  441.          */
  442.         if (THREAD->flags & THREAD_FLAG_USPACE) {
  443.             ipc_cleanup();
  444.                 futex_cleanup();
  445.             klog_printf("Cleanup of task %llu completed.",
  446.                 TASK->taskid);
  447.         }
  448.     }
  449.  
  450. restart:
  451.     ipl = interrupts_disable();
  452.     spinlock_lock(&THREAD->lock);
  453.     if (THREAD->timeout_pending) {
  454.         /* busy waiting for timeouts in progress */
  455.         spinlock_unlock(&THREAD->lock);
  456.         interrupts_restore(ipl);
  457.         goto restart;
  458.     }
  459.    
  460.     THREAD->state = Exiting;
  461.     spinlock_unlock(&THREAD->lock);
  462.     scheduler();
  463.  
  464.     /* Not reached */
  465.     while (1)
  466.         ;
  467. }
  468.  
  469.  
  470. /** Thread sleep
  471.  *
  472.  * Suspend execution of the current thread.
  473.  *
  474.  * @param sec Number of seconds to sleep.
  475.  *
  476.  */
  477. void thread_sleep(uint32_t sec)
  478. {
  479.     thread_usleep(sec * 1000000);
  480. }
  481.  
  482. /** Wait for another thread to exit.
  483.  *
  484.  * @param t Thread to join on exit.
  485.  * @param usec Timeout in microseconds.
  486.  * @param flags Mode of operation.
  487.  *
  488.  * @return An error code from errno.h or an error code from synch.h.
  489.  */
  490. int thread_join_timeout(thread_t *t, uint32_t usec, int flags)
  491. {
  492.     ipl_t ipl;
  493.     int rc;
  494.  
  495.     if (t == THREAD)
  496.         return EINVAL;
  497.  
  498.     /*
  499.      * Since thread join can only be called once on an undetached thread,
  500.      * the thread pointer is guaranteed to be still valid.
  501.      */
  502.    
  503.     ipl = interrupts_disable();
  504.     spinlock_lock(&t->lock);
  505.     ASSERT(!t->detached);
  506.     spinlock_unlock(&t->lock);
  507.     interrupts_restore(ipl);
  508.    
  509.     rc = waitq_sleep_timeout(&t->join_wq, usec, flags);
  510.    
  511.     return rc; 
  512. }
  513.  
  514. /** Detach thread.
  515.  *
  516.  * Mark the thread as detached, if the thread is already in the Lingering
  517.  * state, deallocate its resources.
  518.  *
  519.  * @param t Thread to be detached.
  520.  */
  521. void thread_detach(thread_t *t)
  522. {
  523.     ipl_t ipl;
  524.  
  525.     /*
  526.      * Since the thread is expected not to be already detached,
  527.      * pointer to it must be still valid.
  528.      */
  529.     ipl = interrupts_disable();
  530.     spinlock_lock(&t->lock);
  531.     ASSERT(!t->detached);
  532.     if (t->state == Lingering) {
  533.         thread_destroy(t);  /* unlocks &t->lock */
  534.         interrupts_restore(ipl);
  535.         return;
  536.     } else {
  537.         t->detached = true;
  538.     }
  539.     spinlock_unlock(&t->lock);
  540.     interrupts_restore(ipl);
  541. }
  542.  
  543. /** Thread usleep
  544.  *
  545.  * Suspend execution of the current thread.
  546.  *
  547.  * @param usec Number of microseconds to sleep.
  548.  *
  549.  */
  550. void thread_usleep(uint32_t usec)
  551. {
  552.     waitq_t wq;
  553.                  
  554.     waitq_initialize(&wq);
  555.  
  556.     (void) waitq_sleep_timeout(&wq, usec, SYNCH_FLAGS_NON_BLOCKING);
  557. }
  558.  
  559. /** Register thread out-of-context invocation
  560.  *
  561.  * Register a function and its argument to be executed
  562.  * on next context switch to the current thread.
  563.  *
  564.  * @param call_me      Out-of-context function.
  565.  * @param call_me_with Out-of-context function argument.
  566.  *
  567.  */
  568. void thread_register_call_me(void (* call_me)(void *), void *call_me_with)
  569. {
  570.     ipl_t ipl;
  571.    
  572.     ipl = interrupts_disable();
  573.     spinlock_lock(&THREAD->lock);
  574.     THREAD->call_me = call_me;
  575.     THREAD->call_me_with = call_me_with;
  576.     spinlock_unlock(&THREAD->lock);
  577.     interrupts_restore(ipl);
  578. }
  579.  
  580. static bool thread_walker(avltree_node_t *node, void *arg)
  581. {
  582.     thread_t *t;
  583.        
  584.     t = avltree_get_instance(node, thread_t, threads_tree_node);
  585.  
  586.     uint64_t cycles;
  587.     char suffix;
  588.     order(t->cycles, &cycles, &suffix);
  589.            
  590.     printf("%-6llu %-10s %#10zx %-8s %#10zx %-3ld %#10zx %#10zx %9llu%c ",
  591.         t->tid, t->name, t, thread_states[t->state], t->task,
  592.         t->task->context, t->thread_code, t->kstack, cycles, suffix);
  593.            
  594.     if (t->cpu)
  595.         printf("%-4zd", t->cpu->id);
  596.     else
  597.         printf("none");
  598.            
  599.     if (t->state == Sleeping)
  600.         printf(" %#10zx", t->sleep_queue);
  601.            
  602.     printf("\n");
  603.  
  604.     return true;
  605. }
  606.  
  607. /** Print list of threads debug info */
  608. void thread_print_list(void)
  609. {
  610.     ipl_t ipl;
  611.    
  612.     /* Messing with thread structures, avoid deadlock */
  613.     ipl = interrupts_disable();
  614.     spinlock_lock(&threads_lock);
  615.    
  616.     printf("tid    name       address    state    task       ctx code    "
  617.         "   stack      cycles     cpu  waitqueue\n");
  618.     printf("------ ---------- ---------- -------- ---------- --- --------"
  619.         "-- ---------- ---------- ---- ---------\n");
  620.  
  621.     avltree_walk(&threads_tree, thread_walker, NULL);
  622.  
  623.     spinlock_unlock(&threads_lock);
  624.     interrupts_restore(ipl);
  625. }
  626.  
  627. /** Check whether thread exists.
  628.  *
  629.  * Note that threads_lock must be already held and
  630.  * interrupts must be already disabled.
  631.  *
  632.  * @param t Pointer to thread.
  633.  *
  634.  * @return True if thread t is known to the system, false otherwise.
  635.  */
  636. bool thread_exists(thread_t *t)
  637. {
  638.     avltree_node_t *node;
  639.  
  640.     node = avltree_search(&threads_tree, (avltree_key_t) ((uintptr_t) t));
  641.    
  642.     return node != NULL;
  643. }
  644.  
  645.  
  646. /** Update accounting of current thread.
  647.  *
  648.  * Note that thread_lock on THREAD must be already held and
  649.  * interrupts must be already disabled.
  650.  *
  651.  */
  652. void thread_update_accounting(void)
  653. {
  654.     uint64_t time = get_cycle();
  655.     THREAD->cycles += time - THREAD->last_cycle;
  656.     THREAD->last_cycle = time;
  657. }
  658.  
  659. /** Process syscall to create new thread.
  660.  *
  661.  */
  662. unative_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
  663.     thread_id_t *uspace_thread_id)
  664. {
  665.     thread_t *t;
  666.     char namebuf[THREAD_NAME_BUFLEN];
  667.     uspace_arg_t *kernel_uarg;
  668.     int rc;
  669.  
  670.     rc = copy_from_uspace(namebuf, uspace_name, THREAD_NAME_BUFLEN);
  671.     if (rc != 0)
  672.         return (unative_t) rc;
  673.  
  674.     /*
  675.      * In case of failure, kernel_uarg will be deallocated in this function.
  676.      * In case of success, kernel_uarg will be freed in uinit().
  677.      */
  678.     kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
  679.    
  680.     rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
  681.     if (rc != 0) {
  682.         free(kernel_uarg);
  683.         return (unative_t) rc;
  684.     }
  685.  
  686.     t = thread_create(uinit, kernel_uarg, TASK,
  687.         THREAD_FLAG_USPACE | THREAD_FLAG_NOATTACH, namebuf, false);
  688.     if (t) {
  689.         if (uspace_thread_id != NULL) {
  690.             int rc;
  691.  
  692.             rc = copy_to_uspace(uspace_thread_id, &t->tid,
  693.                 sizeof(t->tid));
  694.             if (rc != 0) {
  695.                 /*
  696.                  * We have encountered a failure, but the thread
  697.                  * has already been created. We need to undo its
  698.                  * creation now.
  699.                  */
  700.  
  701.                 /*
  702.                  * The new thread structure is initialized, but
  703.                  * is still not visible to the system.
  704.                  * We can safely deallocate it.
  705.                  */
  706.                 slab_free(thread_slab, t);
  707.                 free(kernel_uarg);
  708.  
  709.                 return (unative_t) rc;
  710.              }
  711.         }
  712.         thread_attach(t, TASK);
  713.         thread_ready(t);
  714.  
  715.         return 0;
  716.     } else
  717.         free(kernel_uarg);
  718.  
  719.     return (unative_t) ENOMEM;
  720. }
  721.  
  722. /** Process syscall to terminate thread.
  723.  *
  724.  */
  725. unative_t sys_thread_exit(int uspace_status)
  726. {
  727.     thread_exit();
  728.     /* Unreachable */
  729.     return 0;
  730. }
  731.  
  732. /** Syscall for getting TID.
  733.  *
  734.  * @param uspace_thread_id Userspace address of 8-byte buffer where to store
  735.  * current thread ID.
  736.  *
  737.  * @return 0 on success or an error code from @ref errno.h.
  738.  */
  739. unative_t sys_thread_get_id(thread_id_t *uspace_thread_id)
  740. {
  741.     /*
  742.      * No need to acquire lock on THREAD because tid
  743.      * remains constant for the lifespan of the thread.
  744.      */
  745.     return (unative_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
  746.         sizeof(THREAD->tid));
  747. }
  748.  
  749. /** @}
  750.  */
  751.