Subversion Repositories HelenOS

Rev

Rev 382 | Rev 405 | 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. #include <synch/waitq.h>
  30. #include <synch/synch.h>
  31. #include <synch/spinlock.h>
  32. #include <proc/thread.h>
  33. #include <arch/asm.h>
  34. #include <arch/types.h>
  35. #include <time/timeout.h>
  36. #include <arch.h>
  37. #include <context.h>
  38. #include <list.h>
  39.  
  40. /** Initialize wait queue
  41.  *
  42.  * Initialize wait queue.
  43.  *
  44.  * @param wq Pointer to wait queue to be initialized.
  45.  */
  46. void waitq_initialize(waitq_t *wq)
  47. {
  48.     spinlock_initialize(&wq->lock);
  49.     list_initialize(&wq->head);
  50.     wq->missed_wakeups = 0;
  51. }
  52.  
  53. /** Handle timeout during waitq_sleep_timeout() call
  54.  *
  55.  * This routine is called when waitq_sleep_timeout() timeouts.
  56.  * Interrupts are disabled.
  57.  *
  58.  * It is supposed to try to remove 'its' thread from the wait queue;
  59.  * it can eventually fail to achieve this goal when these two events
  60.  * overlap. In that case it behaves just as though there was no
  61.  * timeout at all.
  62.  *
  63.  * @param data Pointer to the thread that called waitq_sleep_timeout().
  64.  */
  65. void waitq_interrupted_sleep(void *data)
  66. {
  67.     thread_t *t = (thread_t *) data;
  68.     waitq_t *wq;
  69.     int do_wakeup = 0;
  70.  
  71.     spinlock_lock(&threads_lock);
  72.     if (!list_member(&t->threads_link, &threads_head))
  73.         goto out;
  74.  
  75. grab_locks:
  76.     spinlock_lock(&t->lock);
  77.     if (wq = t->sleep_queue) {
  78.         if (!spinlock_trylock(&wq->lock)) {
  79.             spinlock_unlock(&t->lock);
  80.             goto grab_locks; /* avoid deadlock */
  81.         }
  82.  
  83.         list_remove(&t->wq_link);
  84.         t->saved_context = t->sleep_timeout_context;
  85.         do_wakeup = 1;
  86.        
  87.         spinlock_unlock(&wq->lock);
  88.         t->sleep_queue = NULL;
  89.     }
  90.    
  91.     t->timeout_pending = 0;
  92.     spinlock_unlock(&t->lock);
  93.    
  94.     if (do_wakeup) thread_ready(t);
  95.  
  96. out:
  97.     spinlock_unlock(&threads_lock);
  98. }
  99.  
  100. /** Sleep until either wakeup or timeout occurs
  101.  *
  102.  * This is a sleep implementation which allows itself to be
  103.  * interrupted from the sleep, restoring a failover context.
  104.  *
  105.  * Sleepers are organised in FIFO fashion in a structure called wait queue.
  106.  *
  107.  * This function is really basic in that other functions as waitq_sleep()
  108.  * and all the *_timeout() functions use it.
  109.  *
  110.  * @param wq Pointer to wait queue.
  111.  * @param usec Timeout in microseconds.
  112.  * @param nonblocking Blocking vs. non-blocking operation mode switch.
  113.  *
  114.  * If usec is greater than zero, regardless of the value of @nonblocking,
  115.  * the call will not return until either timeout or wakeup comes.
  116.  *
  117.  * If usec is zero and nonblocking is zero (false), the call
  118.  * will not return until wakeup comes.
  119.  *
  120.  * If usec is zero and nonblocking is non-zero (true), the call will
  121.  * immediately return, reporting either success or failure.
  122.  *
  123.  * @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
  124.  *         ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
  125.  *
  126.  * ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
  127.  * of the call there was no pending wakeup.
  128.  *
  129.  * ESYNCH_TIMEOUT means that the sleep timed out.
  130.  *
  131.  * ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
  132.  * a pending wakeup at the time of the call. The caller was not put
  133.  * asleep at all.
  134.  *
  135.  * ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
  136.  * attempted.
  137.  */
  138. int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
  139. {
  140.     volatile pri_t pri; /* must be live after context_restore() */
  141.    
  142.    
  143. restart:
  144.     pri = cpu_priority_high();
  145.    
  146.     /*
  147.      * Busy waiting for a delayed timeout.
  148.      * This is an important fix for the race condition between
  149.      * a delayed timeout and a next call to waitq_sleep_timeout().
  150.      * Simply, the thread is not allowed to go to sleep if
  151.      * there are timeouts in progress.
  152.      */
  153.     spinlock_lock(&THREAD->lock);
  154.     if (THREAD->timeout_pending) {
  155.         spinlock_unlock(&THREAD->lock);
  156.         cpu_priority_restore(pri);     
  157.         goto restart;
  158.     }
  159.     spinlock_unlock(&THREAD->lock);
  160.    
  161.     spinlock_lock(&wq->lock);
  162.    
  163.     /* checks whether to go to sleep at all */
  164.     if (wq->missed_wakeups) {
  165.         wq->missed_wakeups--;
  166.         spinlock_unlock(&wq->lock);
  167.         cpu_priority_restore(pri);
  168.         return ESYNCH_OK_ATOMIC;
  169.     }
  170.     else {
  171.         if (nonblocking && (usec == 0)) {
  172.             /* return immediatelly instead of going to sleep */
  173.             spinlock_unlock(&wq->lock);
  174.             cpu_priority_restore(pri);
  175.             return ESYNCH_WOULD_BLOCK;
  176.         }
  177.     }
  178.  
  179.    
  180.     /*
  181.      * Now we are firmly decided to go to sleep.
  182.      */
  183.     spinlock_lock(&THREAD->lock);
  184.     if (usec) {
  185.         /* We use the timeout variant. */
  186.         if (!context_save(&THREAD->sleep_timeout_context)) {
  187.             /*
  188.              * Short emulation of scheduler() return code.
  189.              */
  190.             before_thread_runs();
  191.             spinlock_unlock(&THREAD->lock);
  192.             cpu_priority_restore(pri);
  193.             return ESYNCH_TIMEOUT;
  194.         }
  195.         THREAD->timeout_pending = 1;
  196.         timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_interrupted_sleep, THREAD);
  197.     }
  198.  
  199.     list_append(&THREAD->wq_link, &wq->head);
  200.  
  201.     /*
  202.      * Suspend execution.
  203.      */
  204.     THREAD->state = Sleeping;
  205.     THREAD->sleep_queue = wq;
  206.  
  207.     spinlock_unlock(&THREAD->lock);
  208.  
  209.     scheduler();    /* wq->lock is released in scheduler_separated_stack() */
  210.     cpu_priority_restore(pri);
  211.    
  212.     return ESYNCH_OK_BLOCKED;
  213. }
  214.  
  215.  
  216. /** Wake up first thread sleeping in a wait queue
  217.  *
  218.  * Wake up first thread sleeping in a wait queue.
  219.  * This is the SMP- and IRQ-safe wrapper meant for
  220.  * general use.
  221.  *
  222.  * Besides its 'normal' wakeup operation, it attempts
  223.  * to unregister possible timeout.
  224.  *
  225.  * @param wq Pointer to wait queue.
  226.  * @param all If this is non-zero, all sleeping threads
  227.  *        will be woken up and missed count will be zeroed.
  228.  */
  229. void waitq_wakeup(waitq_t *wq, int all)
  230. {
  231.     pri_t pri;
  232.  
  233.     pri = cpu_priority_high();
  234.     spinlock_lock(&wq->lock);
  235.  
  236.     _waitq_wakeup_unsafe(wq, all);
  237.  
  238.     spinlock_unlock(&wq->lock);
  239.     cpu_priority_restore(pri); 
  240. }
  241.  
  242. /** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
  243.  *
  244.  * This is the internal SMP- and IRQ-unsafe version
  245.  * of waitq_wakeup(). It assumes wq->lock is already
  246.  * locked and interrupts are already disabled.
  247.  *
  248.  * @param wq Pointer to wait queue.
  249.  * @param all If this is non-zero, all sleeping threads
  250.  *        will be woken up and missed count will be zeroed.
  251.  */
  252. void _waitq_wakeup_unsafe(waitq_t *wq, int all)
  253. {
  254.     thread_t *t;
  255.  
  256. loop:  
  257.     if (list_empty(&wq->head)) {
  258.         wq->missed_wakeups++;
  259.         if (all) wq->missed_wakeups = 0;
  260.         return;
  261.     }
  262.  
  263.     t = list_get_instance(wq->head.next, thread_t, wq_link);
  264.    
  265.     list_remove(&t->wq_link);
  266.     spinlock_lock(&t->lock);
  267.     if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
  268.         t->timeout_pending = 0;
  269.     t->sleep_queue = NULL;
  270.     spinlock_unlock(&t->lock);
  271.  
  272.     thread_ready(t);
  273.  
  274.     if (all) goto loop;
  275. }
  276.