Subversion Repositories HelenOS

Rev

Rev 2801 | Rev 2817 | 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/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.     waitq_initialize(&t->go_wq);
  346.  
  347.     /* might depend on previous initialization */
  348.     thread_create_arch(t); 
  349.  
  350.     if (!(flags & THREAD_FLAG_NOATTACH))
  351.         thread_attach(t, task);
  352.  
  353.     return t;
  354. }
  355.  
  356. /** Destroy thread memory structure
  357.  *
  358.  * Detach thread from all queues, cpus etc. and destroy it.
  359.  *
  360.  * Assume thread->lock is held!!
  361.  */
  362. void thread_destroy(thread_t *t)
  363. {
  364.     ASSERT(t->state == Exiting || t->state == Lingering);
  365.     ASSERT(t->task);
  366.     ASSERT(t->cpu);
  367.  
  368.     spinlock_lock(&t->cpu->lock);
  369.     if (t->cpu->fpu_owner == t)
  370.         t->cpu->fpu_owner = NULL;
  371.     spinlock_unlock(&t->cpu->lock);
  372.  
  373.     spinlock_unlock(&t->lock);
  374.  
  375.     spinlock_lock(&threads_lock);
  376.     avltree_delete(&threads_tree, &t->threads_tree_node);
  377.     spinlock_unlock(&threads_lock);
  378.  
  379.     /*
  380.      * Detach from the containing task.
  381.      */
  382.     spinlock_lock(&t->task->lock);
  383.     list_remove(&t->th_link);
  384.     spinlock_unlock(&t->task->lock);   
  385.  
  386.     /*
  387.      * t is guaranteed to be the very last thread of its task.
  388.      * It is safe to destroy the task.
  389.      */
  390.     if (atomic_predec(&t->task->refcount) == 0)
  391.         task_destroy(t->task);
  392.    
  393.     slab_free(thread_slab, t);
  394. }
  395.  
  396. /** Make the thread visible to the system.
  397.  *
  398.  * Attach the thread structure to the current task and make it visible in the
  399.  * threads_tree.
  400.  *
  401.  * @param t Thread to be attached to the task.
  402.  * @param task  Task to which the thread is to be attached.
  403.  */
  404. void thread_attach(thread_t *t, task_t *task)
  405. {
  406.     ipl_t ipl;
  407.  
  408.     /*
  409.      * Attach to the current task.
  410.      */
  411.     ipl = interrupts_disable();
  412.     spinlock_lock(&task->lock);
  413.     atomic_inc(&task->refcount);
  414.     atomic_inc(&task->lifecount);
  415.     ++task->not_stoppable_count;
  416.     list_append(&t->th_link, &task->th_head);
  417.     spinlock_unlock(&task->lock);
  418.  
  419.     /*
  420.      * Register this thread in the system-wide list.
  421.      */
  422.     spinlock_lock(&threads_lock);
  423.     avltree_insert(&threads_tree, &t->threads_tree_node);
  424.     spinlock_unlock(&threads_lock);
  425.    
  426.     interrupts_restore(ipl);
  427. }
  428.  
  429. /** Terminate thread.
  430.  *
  431.  * End current thread execution and switch it to the exiting state. All pending
  432.  * timeouts are executed.
  433.  */
  434. void thread_exit(void)
  435. {
  436.     ipl_t ipl;
  437.  
  438.     if (atomic_predec(&TASK->lifecount) == 0) {
  439.         /*
  440.          * We are the last thread in the task that still has not exited.
  441.          * With the exception of the moment the task was created, new
  442.          * threads can only be created by threads of the same task.
  443.          * We are safe to perform cleanup.
  444.          */
  445.         if (THREAD->flags & THREAD_FLAG_USPACE) {
  446.             ipc_cleanup();
  447.                 futex_cleanup();
  448.             klog_printf("Cleanup of task %llu completed.",
  449.                 TASK->taskid);
  450.         }
  451.     }
  452.  
  453. restart:
  454.     ipl = interrupts_disable();
  455.     spinlock_lock(&THREAD->lock);
  456.     if (THREAD->timeout_pending) {
  457.         /* busy waiting for timeouts in progress */
  458.         spinlock_unlock(&THREAD->lock);
  459.         interrupts_restore(ipl);
  460.         goto restart;
  461.     }
  462.    
  463.     THREAD->state = Exiting;
  464.     spinlock_unlock(&THREAD->lock);
  465.     scheduler();
  466.  
  467.     /* Not reached */
  468.     while (1)
  469.         ;
  470. }
  471.  
  472.  
  473. /** Thread sleep
  474.  *
  475.  * Suspend execution of the current thread.
  476.  *
  477.  * @param sec Number of seconds to sleep.
  478.  *
  479.  */
  480. void thread_sleep(uint32_t sec)
  481. {
  482.     thread_usleep(sec * 1000000);
  483. }
  484.  
  485. /** Wait for another thread to exit.
  486.  *
  487.  * @param t Thread to join on exit.
  488.  * @param usec Timeout in microseconds.
  489.  * @param flags Mode of operation.
  490.  *
  491.  * @return An error code from errno.h or an error code from synch.h.
  492.  */
  493. int thread_join_timeout(thread_t *t, uint32_t usec, int flags)
  494. {
  495.     ipl_t ipl;
  496.     int rc;
  497.  
  498.     if (t == THREAD)
  499.         return EINVAL;
  500.  
  501.     /*
  502.      * Since thread join can only be called once on an undetached thread,
  503.      * the thread pointer is guaranteed to be still valid.
  504.      */
  505.    
  506.     ipl = interrupts_disable();
  507.     spinlock_lock(&t->lock);
  508.     ASSERT(!t->detached);
  509.     spinlock_unlock(&t->lock);
  510.     interrupts_restore(ipl);
  511.    
  512.     rc = waitq_sleep_timeout(&t->join_wq, usec, flags);
  513.    
  514.     return rc; 
  515. }
  516.  
  517. /** Detach thread.
  518.  *
  519.  * Mark the thread as detached, if the thread is already in the Lingering
  520.  * state, deallocate its resources.
  521.  *
  522.  * @param t Thread to be detached.
  523.  */
  524. void thread_detach(thread_t *t)
  525. {
  526.     ipl_t ipl;
  527.  
  528.     /*
  529.      * Since the thread is expected not to be already detached,
  530.      * pointer to it must be still valid.
  531.      */
  532.     ipl = interrupts_disable();
  533.     spinlock_lock(&t->lock);
  534.     ASSERT(!t->detached);
  535.     if (t->state == Lingering) {
  536.         thread_destroy(t);  /* unlocks &t->lock */
  537.         interrupts_restore(ipl);
  538.         return;
  539.     } else {
  540.         t->detached = true;
  541.     }
  542.     spinlock_unlock(&t->lock);
  543.     interrupts_restore(ipl);
  544. }
  545.  
  546. /** Thread usleep
  547.  *
  548.  * Suspend execution of the current thread.
  549.  *
  550.  * @param usec Number of microseconds to sleep.
  551.  *
  552.  */
  553. void thread_usleep(uint32_t usec)
  554. {
  555.     waitq_t wq;
  556.                  
  557.     waitq_initialize(&wq);
  558.  
  559.     (void) waitq_sleep_timeout(&wq, usec, SYNCH_FLAGS_NON_BLOCKING);
  560. }
  561.  
  562. /** Register thread out-of-context invocation
  563.  *
  564.  * Register a function and its argument to be executed
  565.  * on next context switch to the current thread.
  566.  *
  567.  * @param call_me      Out-of-context function.
  568.  * @param call_me_with Out-of-context function argument.
  569.  *
  570.  */
  571. void thread_register_call_me(void (* call_me)(void *), void *call_me_with)
  572. {
  573.     ipl_t ipl;
  574.    
  575.     ipl = interrupts_disable();
  576.     spinlock_lock(&THREAD->lock);
  577.     THREAD->call_me = call_me;
  578.     THREAD->call_me_with = call_me_with;
  579.     spinlock_unlock(&THREAD->lock);
  580.     interrupts_restore(ipl);
  581. }
  582.  
  583. static bool thread_walker(avltree_node_t *node, void *arg)
  584. {
  585.     thread_t *t;
  586.        
  587.     t = avltree_get_instance(node, thread_t, threads_tree_node);
  588.  
  589.     uint64_t cycles;
  590.     char suffix;
  591.     order(t->cycles, &cycles, &suffix);
  592.    
  593.     if (sizeof(void *) == 4)
  594.         printf("%-6llu %-10s %#10zx %-8s %#10zx %-3ld %#10zx %#10zx %9llu%c ",
  595.             t->tid, t->name, t, thread_states[t->state], t->task,
  596.             t->task->context, t->thread_code, t->kstack, cycles, suffix);
  597.     else
  598.         printf("%-6llu %-10s %#18zx %-8s %#18zx %-3ld %#18zx %#18zx %9llu%c ",
  599.             t->tid, t->name, t, thread_states[t->state], t->task,
  600.             t->task->context, t->thread_code, t->kstack, cycles, suffix);
  601.            
  602.     if (t->cpu)
  603.         printf("%-4zd", t->cpu->id);
  604.     else
  605.         printf("none");
  606.            
  607.     if (t->state == Sleeping) {
  608.         if (sizeof(uintptr_t) == 4)
  609.             printf(" %#10zx", t->sleep_queue);
  610.         else
  611.             printf(" %#18zx", t->sleep_queue);
  612.     }
  613.            
  614.     printf("\n");
  615.  
  616.     return true;
  617. }
  618.  
  619. /** Print list of threads debug info */
  620. void thread_print_list(void)
  621. {
  622.     ipl_t ipl;
  623.    
  624.     /* Messing with thread structures, avoid deadlock */
  625.     ipl = interrupts_disable();
  626.     spinlock_lock(&threads_lock);
  627.    
  628.     if (sizeof(uintptr_t) == 4) {
  629.         printf("tid    name       address    state    task       "
  630.             "ctx code       stack      cycles     cpu  "
  631.             "waitqueue\n");
  632.         printf("------ ---------- ---------- -------- ---------- "
  633.             "--- ---------- ---------- ---------- ---- "
  634.             "----------\n");
  635.     } else {
  636.         printf("tid    name       address            state    task               "
  637.             "ctx code               stack              cycles     cpu  "
  638.             "waitqueue\n");
  639.         printf("------ ---------- ------------------ -------- ------------------ "
  640.             "--- ------------------ ------------------ ---------- ---- "
  641.             "------------------\n");
  642.     }
  643.  
  644.     avltree_walk(&threads_tree, thread_walker, NULL);
  645.  
  646.     spinlock_unlock(&threads_lock);
  647.     interrupts_restore(ipl);
  648. }
  649.  
  650. /** Check whether thread exists.
  651.  *
  652.  * Note that threads_lock must be already held and
  653.  * interrupts must be already disabled.
  654.  *
  655.  * @param t Pointer to thread.
  656.  *
  657.  * @return True if thread t is known to the system, false otherwise.
  658.  */
  659. bool thread_exists(thread_t *t)
  660. {
  661.     avltree_node_t *node;
  662.  
  663.     node = avltree_search(&threads_tree, (avltree_key_t) ((uintptr_t) t));
  664.    
  665.     return node != NULL;
  666. }
  667.  
  668.  
  669. /** Update accounting of current thread.
  670.  *
  671.  * Note that thread_lock on THREAD must be already held and
  672.  * interrupts must be already disabled.
  673.  *
  674.  */
  675. void thread_update_accounting(void)
  676. {
  677.     uint64_t time = get_cycle();
  678.     THREAD->cycles += time - THREAD->last_cycle;
  679.     THREAD->last_cycle = time;
  680. }
  681.  
  682. /** Process syscall to create new thread.
  683.  *
  684.  */
  685. unative_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
  686.     thread_id_t *uspace_thread_id)
  687. {
  688.     thread_t *t;
  689.     char namebuf[THREAD_NAME_BUFLEN];
  690.     uspace_arg_t *kernel_uarg;
  691.     int rc;
  692.  
  693.     rc = copy_from_uspace(namebuf, uspace_name, THREAD_NAME_BUFLEN);
  694.     if (rc != 0)
  695.         return (unative_t) rc;
  696.  
  697.     /*
  698.      * In case of failure, kernel_uarg will be deallocated in this function.
  699.      * In case of success, kernel_uarg will be freed in uinit().
  700.      */
  701.     kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
  702.    
  703.     rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
  704.     if (rc != 0) {
  705.         free(kernel_uarg);
  706.         return (unative_t) rc;
  707.     }
  708.  
  709.     t = thread_create(uinit, kernel_uarg, TASK,
  710.         THREAD_FLAG_USPACE | THREAD_FLAG_NOATTACH, namebuf, false);
  711.     if (t) {
  712.         if (uspace_thread_id != NULL) {
  713.             int rc;
  714.  
  715.             rc = copy_to_uspace(uspace_thread_id, &t->tid,
  716.                 sizeof(t->tid));
  717.             if (rc != 0) {
  718.                 /*
  719.                  * We have encountered a failure, but the thread
  720.                  * has already been created. We need to undo its
  721.                  * creation now.
  722.                  */
  723.  
  724.                 /*
  725.                  * The new thread structure is initialized, but
  726.                  * is still not visible to the system.
  727.                  * We can safely deallocate it.
  728.                  */
  729.                 slab_free(thread_slab, t);
  730.                 free(kernel_uarg);
  731.  
  732.                 return (unative_t) rc;
  733.              }
  734.         }
  735.         thread_attach(t, TASK);
  736.         thread_ready(t);
  737.  
  738.         return 0;
  739.     } else
  740.         free(kernel_uarg);
  741.  
  742.     return (unative_t) ENOMEM;
  743. }
  744.  
  745. /** Process syscall to terminate thread.
  746.  *
  747.  */
  748. unative_t sys_thread_exit(int uspace_status)
  749. {
  750.     thread_exit();
  751.     /* Unreachable */
  752.     return 0;
  753. }
  754.  
  755. /** Syscall for getting TID.
  756.  *
  757.  * @param uspace_thread_id Userspace address of 8-byte buffer where to store
  758.  * current thread ID.
  759.  *
  760.  * @return 0 on success or an error code from @ref errno.h.
  761.  */
  762. unative_t sys_thread_get_id(thread_id_t *uspace_thread_id)
  763. {
  764.     /*
  765.      * No need to acquire lock on THREAD because tid
  766.      * remains constant for the lifespan of the thread.
  767.      */
  768.     return (unative_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
  769.         sizeof(THREAD->tid));
  770. }
  771.  
  772. /** @}
  773.  */
  774.