util/coroutine-gthread.c

   1 /*
   2  * GThread coroutine initialization code
   3  *
   4  * Copyright (C) 2006  Anthony Liguori <[email protected]>
   5  * Copyright (C) 2011  Aneesh Kumar K.V <[email protected]>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.0 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include "qemu/osdep.h"
  22 #include <glib.h>
  23 #include "qemu-common.h"
  24 #include "qemu/coroutine_int.h"
  25
  26 typedef struct {
  27     Coroutine base;
  28     GThread *thread;
  29     bool runnable;
  30     bool free_on_thread_exit;
  31     CoroutineAction action;
  32 } CoroutineGThread;
  33
  34 static CompatGMutex coroutine_lock;
  35 static CompatGCond coroutine_cond;
  36
  37 /* GLib 2.31 and beyond deprecated various parts of the thread API,
  38  * but the new interfaces are not available in older GLib versions
  39  * so we have to cope with both.
  40  */
  41 #if GLIB_CHECK_VERSION(2, 31, 0)
  42 /* Awkwardly, the GPrivate API doesn't provide a way to update the
  43  * GDestroyNotify handler for the coroutine key dynamically. So instead
  44  * we track whether or not the CoroutineGThread should be freed on
  45  * thread exit / coroutine key update using the free_on_thread_exit
  46  * field.
  47  */
  48 static void coroutine_destroy_notify(gpointer data)
  49 {
  50     CoroutineGThread *co = data;
  51     if (co && co->free_on_thread_exit) {
  52         g_free(co);
  53     }
  54 }
  55
  56 static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify);
  57
  58 static inline CoroutineGThread *get_coroutine_key(void)
  59 {
  60     return g_private_get(&coroutine_key);
  61 }
  62
  63 static inline void set_coroutine_key(CoroutineGThread *co,
  64                                      bool free_on_thread_exit)
  65 {
  66     /* Unlike g_static_private_set() this does not call the GDestroyNotify
  67      * if the previous value of the key was NULL. Fortunately we only need
  68      * the GDestroyNotify in the non-NULL key case.
  69      */
  70     co->free_on_thread_exit = free_on_thread_exit;
  71     g_private_replace(&coroutine_key, co);
  72 }
  73
  74 static inline GThread *create_thread(GThreadFunc func, gpointer data)
  75 {
  76     return g_thread_new("coroutine", func, data);
  77 }
  78
  79 #else
  80
  81 /* Handle older GLib versions */
  82
  83 static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT;
  84
  85 static inline CoroutineGThread *get_coroutine_key(void)
  86 {
  87     return g_static_private_get(&coroutine_key);
  88 }
  89
  90 static inline void set_coroutine_key(CoroutineGThread *co,
  91                                      bool free_on_thread_exit)
  92 {
  93     g_static_private_set(&coroutine_key, co,
  94                          free_on_thread_exit ? (GDestroyNotify)g_free : NULL);
  95 }
  96
  97 static inline GThread *create_thread(GThreadFunc func, gpointer data)
  98 {
  99     return g_thread_create_full(func, data, 0, TRUE, TRUE,
 100                                 G_THREAD_PRIORITY_NORMAL, NULL);
 101 }
 102
 103 #endif
 104
 105
 106 static void __attribute__((constructor)) coroutine_init(void)
 107 {
 108 #if !GLIB_CHECK_VERSION(2, 31, 0)
 109     if (!g_thread_supported()) {
 110         g_thread_init(NULL);
 111     }
 112 #endif
 113 }
 114
 115 static void coroutine_wait_runnable_locked(CoroutineGThread *co)
 116 {
 117     while (!co->runnable) {
 118         g_cond_wait(&coroutine_cond, &coroutine_lock);
 119     }
 120 }
 121
 122 static void coroutine_wait_runnable(CoroutineGThread *co)
 123 {
 124     g_mutex_lock(&coroutine_lock);
 125     coroutine_wait_runnable_locked(co);
 126     g_mutex_unlock(&coroutine_lock);
 127 }
 128
 129 static gpointer coroutine_thread(gpointer opaque)
 130 {
 131     CoroutineGThread *co = opaque;
 132
 133     set_coroutine_key(co, false);
 134     coroutine_wait_runnable(co);
 135     co->base.entry(co->base.entry_arg);
 136     qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE);
 137     return NULL;
 138 }
 139
 140 Coroutine *qemu_coroutine_new(void)
 141 {
 142     CoroutineGThread *co;
 143
 144     co = g_malloc0(sizeof(*co));
 145     co->thread = create_thread(coroutine_thread, co);
 146     if (!co->thread) {
 147         g_free(co);
 148         return NULL;
 149     }
 150     return &co->base;
 151 }
 152
 153 void qemu_coroutine_delete(Coroutine *co_)
 154 {
 155     CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_);
 156
 157     g_thread_join(co->thread);
 158     g_free(co);
 159 }
 160
 161 CoroutineAction qemu_coroutine_switch(Coroutine *from_,
 162                                       Coroutine *to_,
 163                                       CoroutineAction action)
 164 {
 165     CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_);
 166     CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_);
 167
 168     g_mutex_lock(&coroutine_lock);
 169     from->runnable = false;
 170     from->action = action;
 171     to->runnable = true;
 172     to->action = action;
 173     g_cond_broadcast(&coroutine_cond);
 174
 175     if (action != COROUTINE_TERMINATE) {
 176         coroutine_wait_runnable_locked(from);
 177     }
 178     g_mutex_unlock(&coroutine_lock);
 179     return from->action;
 180 }
 181
 182 Coroutine *qemu_coroutine_self(void)
 183 {
 184     CoroutineGThread *co = get_coroutine_key();
 185     if (!co) {
 186         co = g_malloc0(sizeof(*co));
 187         co->runnable = true;
 188         set_coroutine_key(co, true);
 189     }
 190
 191     return &co->base;
 192 }
 193
 194 bool qemu_in_coroutine(void)
 195 {
 196     CoroutineGThread *co = get_coroutine_key();
 197
 198     return co && co->base.caller;
 199 }