coroutine-gthread.c

   1 /*
   2  * GThread coroutine initialization code
   3  *
   4  * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
   5  * Copyright (C) 2011  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
   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 <glib.h>
  22 #include "qemu-common.h"
  23 #include "block/coroutine_int.h"
  24
  25 typedef struct {
  26     Coroutine base;
  27     GThread *thread;
  28     bool runnable;
  29     bool free_on_thread_exit;
  30     CoroutineAction action;
  31 } CoroutineGThread;
  32
  33 static GStaticMutex coroutine_lock = G_STATIC_MUTEX_INIT;
  34
  35 /* GLib 2.31 and beyond deprecated various parts of the thread API,
  36  * but the new interfaces are not available in older GLib versions
  37  * so we have to cope with both.
  38  */
  39 #if GLIB_CHECK_VERSION(2, 31, 0)
  40 /* Default zero-initialisation is sufficient for 2.31+ GCond */
  41 static GCond the_coroutine_cond;
  42 static GCond *coroutine_cond = &the_coroutine_cond;
  43 static inline void init_coroutine_cond(void)
  44 {
  45 }
  46
  47 /* Awkwardly, the GPrivate API doesn't provide a way to update the
  48  * GDestroyNotify handler for the coroutine key dynamically. So instead
  49  * we track whether or not the CoroutineGThread should be freed on
  50  * thread exit / coroutine key update using the free_on_thread_exit
  51  * field.
  52  */
  53 static void coroutine_destroy_notify(gpointer data)
  54 {
  55     CoroutineGThread *co = data;
  56     if (co && co->free_on_thread_exit) {
  57         g_free(co);
  58     }
  59 }
  60
  61 static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify);
  62
  63 static inline CoroutineGThread *get_coroutine_key(void)
  64 {
  65     return g_private_get(&coroutine_key);
  66 }
  67
  68 static inline void set_coroutine_key(CoroutineGThread *co,
  69                                      bool free_on_thread_exit)
  70 {
  71     /* Unlike g_static_private_set() this does not call the GDestroyNotify
  72      * if the previous value of the key was NULL. Fortunately we only need
  73      * the GDestroyNotify in the non-NULL key case.
  74      */
  75     co->free_on_thread_exit = free_on_thread_exit;
  76     g_private_replace(&coroutine_key, co);
  77 }
  78
  79 static inline GThread *create_thread(GThreadFunc func, gpointer data)
  80 {
  81     return g_thread_new("coroutine", func, data);
  82 }
  83
  84 #else
  85
  86 /* Handle older GLib versions */
  87 static GCond *coroutine_cond;
  88 static inline void init_coroutine_cond(void)
  89 {
  90     coroutine_cond = g_cond_new();
  91 }
  92
  93 static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT;
  94
  95 static inline CoroutineGThread *get_coroutine_key(void)
  96 {
  97     return g_static_private_get(&coroutine_key);
  98 }
  99
 100 static inline void set_coroutine_key(CoroutineGThread *co,
 101                                      bool free_on_thread_exit)
 102 {
 103     g_static_private_set(&coroutine_key, co,
 104                          free_on_thread_exit ? (GDestroyNotify)g_free : NULL);
 105 }
 106
 107 static inline GThread *create_thread(GThreadFunc func, gpointer data)
 108 {
 109     return g_thread_create_full(func, data, 0, TRUE, TRUE,
 110                                 G_THREAD_PRIORITY_NORMAL, NULL);
 111 }
 112
 113 #endif
 114
 115
 116 static void __attribute__((constructor)) coroutine_init(void)
 117 {
 118     if (!g_thread_supported()) {
 119 #if !GLIB_CHECK_VERSION(2, 31, 0)
 120         g_thread_init(NULL);
 121 #else
 122         fprintf(stderr, "glib threading failed to initialize.\n");
 123         exit(1);
 124 #endif
 125     }
 126
 127     init_coroutine_cond();
 128 }
 129
 130 static void coroutine_wait_runnable_locked(CoroutineGThread *co)
 131 {
 132     while (!co->runnable) {
 133         g_cond_wait(coroutine_cond, g_static_mutex_get_mutex(&coroutine_lock));
 134     }
 135 }
 136
 137 static void coroutine_wait_runnable(CoroutineGThread *co)
 138 {
 139     g_static_mutex_lock(&coroutine_lock);
 140     coroutine_wait_runnable_locked(co);
 141     g_static_mutex_unlock(&coroutine_lock);
 142 }
 143
 144 static gpointer coroutine_thread(gpointer opaque)
 145 {
 146     CoroutineGThread *co = opaque;
 147
 148     set_coroutine_key(co, false);
 149     coroutine_wait_runnable(co);
 150     co->base.entry(co->base.entry_arg);
 151     qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE);
 152     return NULL;
 153 }
 154
 155 Coroutine *qemu_coroutine_new(void)
 156 {
 157     CoroutineGThread *co;
 158
 159     co = g_malloc0(sizeof(*co));
 160     co->thread = create_thread(coroutine_thread, co);
 161     if (!co->thread) {
 162         g_free(co);
 163         return NULL;
 164     }
 165     return &co->base;
 166 }
 167
 168 void qemu_coroutine_delete(Coroutine *co_)
 169 {
 170     CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_);
 171
 172     g_thread_join(co->thread);
 173     g_free(co);
 174 }
 175
 176 CoroutineAction qemu_coroutine_switch(Coroutine *from_,
 177                                       Coroutine *to_,
 178                                       CoroutineAction action)
 179 {
 180     CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_);
 181     CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_);
 182
 183     g_static_mutex_lock(&coroutine_lock);
 184     from->runnable = false;
 185     from->action = action;
 186     to->runnable = true;
 187     to->action = action;
 188     g_cond_broadcast(coroutine_cond);
 189
 190     if (action != COROUTINE_TERMINATE) {
 191         coroutine_wait_runnable_locked(from);
 192     }
 193     g_static_mutex_unlock(&coroutine_lock);
 194     return from->action;
 195 }
 196
 197 Coroutine *qemu_coroutine_self(void)
 198 {
 199     CoroutineGThread *co = get_coroutine_key();
 200     if (!co) {
 201         co = g_malloc0(sizeof(*co));
 202         co->runnable = true;
 203         set_coroutine_key(co, true);
 204     }
 205
 206     return &co->base;
 207 }
 208
 209 bool qemu_in_coroutine(void)
 210 {
 211     CoroutineGThread *co = get_coroutine_key();
 212
 213     return co && co->base.caller;
 214 }