Subversion Repositories HelenOS

Rev

Rev 2436 | Rev 2451 | 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.         ASSERT(t->cpu != NULL);
  242.         cpu = t->cpu;
  243.     }
  244.     t->state = Ready;
  245.     spinlock_unlock(&t->lock);
  246.    
  247.     /*
  248.      * Append t to respective ready queue on respective processor.
  249.      */
  250.     r = &cpu->rq[i];
  251.     spinlock_lock(&r->lock);
  252.     list_append(&t->rq_link, &r->rq_head);
  253.     r->n++;
  254.     spinlock_unlock(&r->lock);
  255.  
  256.     atomic_inc(&nrdy);
  257.     avg = atomic_get(&nrdy) / config.cpu_active;
  258.     atomic_inc(&cpu->nrdy);
  259.  
  260.     interrupts_restore(ipl);
  261. }
  262.  
  263. /** Create new thread
  264.  *
  265.  * Create a new thread.
  266.  *
  267.  * @param func      Thread's implementing function.
  268.  * @param arg       Thread's implementing function argument.
  269.  * @param task      Task to which the thread belongs.
  270.  * @param flags     Thread flags.
  271.  * @param name      Symbolic name.
  272.  * @param uncounted Thread's accounting doesn't affect accumulated task
  273.  *          accounting.
  274.  *
  275.  * @return New thread's structure on success, NULL on failure.
  276.  *
  277.  */
  278. thread_t *thread_create(void (* func)(void *), void *arg, task_t *task,
  279.     int flags, char *name, bool uncounted)
  280. {
  281.     thread_t *t;
  282.     ipl_t ipl;
  283.    
  284.     t = (thread_t *) slab_alloc(thread_slab, 0);
  285.     if (!t)
  286.         return NULL;
  287.    
  288.     /* Not needed, but good for debugging */
  289.     memsetb((uintptr_t) t->kstack, THREAD_STACK_SIZE * 1 << STACK_FRAMES,
  290.         0);
  291.    
  292.     ipl = interrupts_disable();
  293.     spinlock_lock(&tidlock);
  294.     t->tid = ++last_tid;
  295.     spinlock_unlock(&tidlock);
  296.     interrupts_restore(ipl);
  297.    
  298.     context_save(&t->saved_context);
  299.     context_set(&t->saved_context, FADDR(cushion), (uintptr_t) t->kstack,
  300.         THREAD_STACK_SIZE);
  301.    
  302.     the_initialize((the_t *) t->kstack);
  303.    
  304.     ipl = interrupts_disable();
  305.     t->saved_context.ipl = interrupts_read();
  306.     interrupts_restore(ipl);
  307.    
  308.     memcpy(t->name, name, THREAD_NAME_BUFLEN);
  309.    
  310.     t->thread_code = func;
  311.     t->thread_arg = arg;
  312.     t->ticks = -1;
  313.     t->cycles = 0;
  314.     t->uncounted = uncounted;
  315.     t->priority = -1;       /* start in rq[0] */
  316.     t->cpu = NULL;
  317.     t->flags = flags;
  318.     t->state = Entering;
  319.     t->call_me = NULL;
  320.     t->call_me_with = NULL;
  321.    
  322.     timeout_initialize(&t->sleep_timeout);
  323.     t->sleep_interruptible = false;
  324.     t->sleep_queue = NULL;
  325.     t->timeout_pending = 0;
  326.  
  327.     t->in_copy_from_uspace = false;
  328.     t->in_copy_to_uspace = false;
  329.  
  330.     t->interrupted = false;
  331.     t->join_type = None;
  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.     ipl = interrupts_disable();  
  346.     spinlock_lock(&task->lock);
  347.     if (!task->accept_new_threads) {
  348.         spinlock_unlock(&task->lock);
  349.         slab_free(thread_slab, t);
  350.         interrupts_restore(ipl);
  351.         return NULL;
  352.     } else {
  353.         /*
  354.          * Bump the reference count so that this task cannot be
  355.          * destroyed while the new thread is being attached to it.
  356.          */
  357.         task->refcount++;
  358.     }
  359.     spinlock_unlock(&task->lock);
  360.     interrupts_restore(ipl);
  361.  
  362.     if (!(flags & THREAD_FLAG_NOATTACH))
  363.         thread_attach(t, task);
  364.  
  365.     return t;
  366. }
  367.  
  368. /** Destroy thread memory structure
  369.  *
  370.  * Detach thread from all queues, cpus etc. and destroy it.
  371.  *
  372.  * Assume thread->lock is held!!
  373.  */
  374. void thread_destroy(thread_t *t)
  375. {
  376.     bool destroy_task = false;
  377.  
  378.     ASSERT(t->state == Exiting || t->state == Undead);
  379.     ASSERT(t->task);
  380.     ASSERT(t->cpu);
  381.  
  382.     spinlock_lock(&t->cpu->lock);
  383.     if (t->cpu->fpu_owner == t)
  384.         t->cpu->fpu_owner = NULL;
  385.     spinlock_unlock(&t->cpu->lock);
  386.  
  387.     spinlock_unlock(&t->lock);
  388.  
  389.     spinlock_lock(&threads_lock);
  390.     btree_remove(&threads_btree, (btree_key_t) ((uintptr_t ) t), NULL);
  391.     spinlock_unlock(&threads_lock);
  392.  
  393.     /*
  394.      * Detach from the containing task.
  395.      */
  396.     spinlock_lock(&t->task->lock);
  397.     list_remove(&t->th_link);
  398.     if (--t->task->refcount == 0) {
  399.         t->task->accept_new_threads = false;
  400.         destroy_task = true;
  401.     }
  402.     spinlock_unlock(&t->task->lock);   
  403.    
  404.     if (destroy_task)
  405.         task_destroy(t->task);
  406.    
  407.     /*
  408.      * If the thread had a userspace context, free up its kernel_uarg
  409.      * structure.
  410.      */
  411.     if (t->flags & THREAD_FLAG_USPACE) {
  412.         ASSERT(t->thread_arg);
  413.         free(t->thread_arg);
  414.     }
  415.  
  416.     slab_free(thread_slab, t);
  417. }
  418.  
  419. /** Make the thread visible to the system.
  420.  *
  421.  * Attach the thread structure to the current task and make it visible in the
  422.  * threads_btree.
  423.  *
  424.  * @param t Thread to be attached to the task.
  425.  * @param task  Task to which the thread is to be attached.
  426.  */
  427. void thread_attach(thread_t *t, task_t *task)
  428. {
  429.     ipl_t ipl;
  430.  
  431.     /*
  432.      * Attach to the current task.
  433.      */
  434.     ipl = interrupts_disable();  
  435.     spinlock_lock(&task->lock);
  436.     ASSERT(task->refcount);
  437.     list_append(&t->th_link, &task->th_head);
  438.     if (task->refcount == 1)
  439.         task->main_thread = t;
  440.     spinlock_unlock(&task->lock);
  441.  
  442.     /*
  443.      * Register this thread in the system-wide list.
  444.      */
  445.     spinlock_lock(&threads_lock);
  446.     btree_insert(&threads_btree, (btree_key_t) ((uintptr_t) t), (void *) t,
  447.         NULL);
  448.     spinlock_unlock(&threads_lock);
  449.    
  450.     interrupts_restore(ipl);
  451. }
  452.  
  453. /** Terminate thread.
  454.  *
  455.  * End current thread execution and switch it to the exiting state. All pending
  456.  * timeouts are executed.
  457.  */
  458. void thread_exit(void)
  459. {
  460.     ipl_t ipl;
  461.  
  462. restart:
  463.     ipl = interrupts_disable();
  464.     spinlock_lock(&THREAD->lock);
  465.     if (THREAD->timeout_pending) {
  466.         /* busy waiting for timeouts in progress */
  467.         spinlock_unlock(&THREAD->lock);
  468.         interrupts_restore(ipl);
  469.         goto restart;
  470.     }
  471.     THREAD->state = Exiting;
  472.     spinlock_unlock(&THREAD->lock);
  473.     scheduler();
  474.  
  475.     /* Not reached */
  476.     while (1)
  477.         ;
  478. }
  479.  
  480.  
  481. /** Thread sleep
  482.  *
  483.  * Suspend execution of the current thread.
  484.  *
  485.  * @param sec Number of seconds to sleep.
  486.  *
  487.  */
  488. void thread_sleep(uint32_t sec)
  489. {
  490.     thread_usleep(sec * 1000000);
  491. }
  492.  
  493. /** Wait for another thread to exit.
  494.  *
  495.  * @param t Thread to join on exit.
  496.  * @param usec Timeout in microseconds.
  497.  * @param flags Mode of operation.
  498.  *
  499.  * @return An error code from errno.h or an error code from synch.h.
  500.  */
  501. int thread_join_timeout(thread_t *t, uint32_t usec, int flags)
  502. {
  503.     ipl_t ipl;
  504.     int rc;
  505.  
  506.     if (t == THREAD)
  507.         return EINVAL;
  508.  
  509.     /*
  510.      * Since thread join can only be called once on an undetached thread,
  511.      * the thread pointer is guaranteed to be still valid.
  512.      */
  513.    
  514.     ipl = interrupts_disable();
  515.     spinlock_lock(&t->lock);
  516.     ASSERT(!t->detached);
  517.     spinlock_unlock(&t->lock);
  518.     interrupts_restore(ipl);
  519.    
  520.     rc = waitq_sleep_timeout(&t->join_wq, usec, flags);
  521.    
  522.     return rc; 
  523. }
  524.  
  525. /** Detach thread.
  526.  *
  527.  * Mark the thread as detached, if the thread is already in the Undead state,
  528.  * deallocate its resources.
  529.  *
  530.  * @param t Thread to be detached.
  531.  */
  532. void thread_detach(thread_t *t)
  533. {
  534.     ipl_t ipl;
  535.  
  536.     /*
  537.      * Since the thread is expected not to be already detached,
  538.      * pointer to it must be still valid.
  539.      */
  540.     ipl = interrupts_disable();
  541.     spinlock_lock(&t->lock);
  542.     ASSERT(!t->detached);
  543.     if (t->state == Undead) {
  544.         thread_destroy(t);  /* unlocks &t->lock */
  545.         interrupts_restore(ipl);
  546.         return;
  547.     } else {
  548.         t->detached = true;
  549.     }
  550.     spinlock_unlock(&t->lock);
  551.     interrupts_restore(ipl);
  552. }
  553.  
  554. /** Thread usleep
  555.  *
  556.  * Suspend execution of the current thread.
  557.  *
  558.  * @param usec Number of microseconds to sleep.
  559.  *
  560.  */
  561. void thread_usleep(uint32_t usec)
  562. {
  563.     waitq_t wq;
  564.                  
  565.     waitq_initialize(&wq);
  566.  
  567.     (void) waitq_sleep_timeout(&wq, usec, SYNCH_FLAGS_NON_BLOCKING);
  568. }
  569.  
  570. /** Register thread out-of-context invocation
  571.  *
  572.  * Register a function and its argument to be executed
  573.  * on next context switch to the current thread.
  574.  *
  575.  * @param call_me      Out-of-context function.
  576.  * @param call_me_with Out-of-context function argument.
  577.  *
  578.  */
  579. void thread_register_call_me(void (* call_me)(void *), void *call_me_with)
  580. {
  581.     ipl_t ipl;
  582.    
  583.     ipl = interrupts_disable();
  584.     spinlock_lock(&THREAD->lock);
  585.     THREAD->call_me = call_me;
  586.     THREAD->call_me_with = call_me_with;
  587.     spinlock_unlock(&THREAD->lock);
  588.     interrupts_restore(ipl);
  589. }
  590.  
  591. /** Print list of threads debug info */
  592. void thread_print_list(void)
  593. {
  594.     link_t *cur;
  595.     ipl_t ipl;
  596.    
  597.     /* Messing with thread structures, avoid deadlock */
  598.     ipl = interrupts_disable();
  599.     spinlock_lock(&threads_lock);
  600.    
  601.     printf("tid    name       address    state    task       ctx code    "
  602.         "   stack      cycles     cpu  kstack     waitqueue\n");
  603.     printf("------ ---------- ---------- -------- ---------- --- --------"
  604.         "-- ---------- ---------- ---- ---------- ----------\n");
  605.  
  606.     for (cur = threads_btree.leaf_head.next;
  607.         cur != &threads_btree.leaf_head; cur = cur->next) {
  608.         btree_node_t *node;
  609.         unsigned int i;
  610.  
  611.         node = list_get_instance(cur, btree_node_t, leaf_link);
  612.         for (i = 0; i < node->keys; i++) {
  613.             thread_t *t;
  614.        
  615.             t = (thread_t *) node->value[i];
  616.            
  617.             uint64_t cycles;
  618.             char suffix;
  619.             order(t->cycles, &cycles, &suffix);
  620.            
  621.             printf("%-6llu %-10s %#10zx %-8s %#10zx %-3ld %#10zx "
  622.                 "%#10zx %9llu%c ", t->tid, t->name, t,
  623.                 thread_states[t->state], t->task, t->task->context,
  624.                 t->thread_code, t->kstack, cycles, suffix);
  625.            
  626.             if (t->cpu)
  627.                 printf("%-4zd", t->cpu->id);
  628.             else
  629.                 printf("none");
  630.            
  631.             if (t->state == Sleeping)
  632.                 printf(" %#10zx %#10zx", t->kstack,
  633.                     t->sleep_queue);
  634.            
  635.             printf("\n");
  636.         }
  637.     }
  638.  
  639.     spinlock_unlock(&threads_lock);
  640.     interrupts_restore(ipl);
  641. }
  642.  
  643. /** Check whether thread exists.
  644.  *
  645.  * Note that threads_lock must be already held and
  646.  * interrupts must be already disabled.
  647.  *
  648.  * @param t Pointer to thread.
  649.  *
  650.  * @return True if thread t is known to the system, false otherwise.
  651.  */
  652. bool thread_exists(thread_t *t)
  653. {
  654.     btree_node_t *leaf;
  655.    
  656.     return btree_search(&threads_btree, (btree_key_t) ((uintptr_t) t),
  657.         &leaf) != NULL;
  658. }
  659.  
  660.  
  661. /** Update accounting of current thread.
  662.  *
  663.  * Note that thread_lock on THREAD must be already held and
  664.  * interrupts must be already disabled.
  665.  *
  666.  */
  667. void thread_update_accounting(void)
  668. {
  669.     uint64_t time = get_cycle();
  670.     THREAD->cycles += time - THREAD->last_cycle;
  671.     THREAD->last_cycle = time;
  672. }
  673.  
  674. /** Process syscall to create new thread.
  675.  *
  676.  */
  677. unative_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
  678.     thread_id_t *uspace_thread_id)
  679. {
  680.     thread_t *t;
  681.     char namebuf[THREAD_NAME_BUFLEN];
  682.     uspace_arg_t *kernel_uarg;
  683.     int rc;
  684.  
  685.     rc = copy_from_uspace(namebuf, uspace_name, THREAD_NAME_BUFLEN);
  686.     if (rc != 0)
  687.         return (unative_t) rc;
  688.  
  689.     kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
  690.     rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
  691.     if (rc != 0) {
  692.         free(kernel_uarg);
  693.         return (unative_t) rc;
  694.     }
  695.  
  696.     t = thread_create(uinit, kernel_uarg, TASK,
  697.         THREAD_FLAG_USPACE | THREAD_FLAG_NOATTACH, namebuf, false);
  698.     if (t) {
  699.         if (uspace_thread_id != NULL) {
  700.             int rc;
  701.  
  702.             rc = copy_to_uspace(uspace_thread_id, &t->tid,
  703.                 sizeof(t->tid));
  704.             if (rc != 0) {
  705.                 ipl_t ipl;
  706.  
  707.                 /*
  708.                  * We have encountered a failure, but the thread
  709.                  * has already been created. We need to undo its
  710.                  * creation now.
  711.                  */
  712.  
  713.                 /*
  714.                  * The new thread structure is initialized,
  715.                  * but is still not visible to the system.
  716.                  * We can safely deallocate it.
  717.                  */
  718.                 slab_free(thread_slab, t);
  719.                 free(kernel_uarg);
  720.  
  721.                 /*
  722.                  * Now we need to decrement the task reference
  723.                  * counter. Because we are running within the
  724.                  * same task, thread t is not the last thread
  725.                  * in the task, so it is safe to merely
  726.                  * decrement the counter.
  727.                  */
  728.                 ipl = interrupts_disable();
  729.                 spinlock_lock(&TASK->lock);
  730.                 TASK->refcount--;
  731.                 spinlock_unlock(&TASK->lock);
  732.                 interrupts_restore(ipl);
  733.  
  734.                 return (unative_t) rc;
  735.              }
  736.         }
  737.         thread_attach(t, TASK);
  738.         thread_ready(t);
  739.  
  740.         return 0;
  741.     } else
  742.         free(kernel_uarg);
  743.  
  744.     return (unative_t) ENOMEM;
  745. }
  746.  
  747. /** Process syscall to terminate thread.
  748.  *
  749.  */
  750. unative_t sys_thread_exit(int uspace_status)
  751. {
  752.     thread_exit();
  753.     /* Unreachable */
  754.     return 0;
  755. }
  756.  
  757. /** Syscall for getting TID.
  758.  *
  759.  * @param uspace_thread_id Userspace address of 8-byte buffer where to store
  760.  * current thread ID.
  761.  *
  762.  * @return 0 on success or an error code from @ref errno.h.
  763.  */
  764. unative_t sys_thread_get_id(thread_id_t *uspace_thread_id)
  765. {
  766.     /*
  767.      * No need to acquire lock on THREAD because tid
  768.      * remains constant for the lifespan of the thread.
  769.      */
  770.     return (unative_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
  771.         sizeof(THREAD->tid));
  772. }
  773.  
  774. /** @}
  775.  */
  776.