qemu-coroutine.c

   1 /*
   2  * QEMU coroutines
   3  *
   4  * Copyright IBM, Corp. 2011
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>
   8  *  Kevin Wolf         <kwolf@redhat.com>
   9  *
  10  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  11  * See the COPYING.LIB file in the top-level directory.
  12  *
  13  */
  14
  15 #include "trace.h"
  16 #include "qemu-common.h"
  17 #include "qemu/thread.h"
  18 #include "block/coroutine.h"
  19 #include "block/coroutine_int.h"
  20
  21 enum {
  22     /* Maximum free pool size prevents holding too many freed coroutines */
  23     POOL_MAX_SIZE = 64,
  24 };
  25
  26 /** Free list to speed up creation */
  27 static QemuMutex pool_lock;
  28 static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
  29 static unsigned int pool_size;
  30
  31 Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
  32 {
  33     Coroutine *co = NULL;
  34
  35     if (CONFIG_COROUTINE_POOL) {
  36         qemu_mutex_lock(&pool_lock);
  37         co = QSLIST_FIRST(&pool);
  38         if (co) {
  39             QSLIST_REMOVE_HEAD(&pool, pool_next);
  40             pool_size--;
  41         }
  42         qemu_mutex_unlock(&pool_lock);
  43     }
  44
  45     if (!co) {
  46         co = qemu_coroutine_new();
  47     }
  48
  49     co->entry = entry;
  50     QTAILQ_INIT(&co->co_queue_wakeup);
  51     return co;
  52 }
  53
  54 static void coroutine_delete(Coroutine *co)
  55 {
  56     if (CONFIG_COROUTINE_POOL) {
  57         qemu_mutex_lock(&pool_lock);
  58         if (pool_size < POOL_MAX_SIZE) {
  59             QSLIST_INSERT_HEAD(&pool, co, pool_next);
  60             co->caller = NULL;
  61             pool_size++;
  62             qemu_mutex_unlock(&pool_lock);
  63             return;
  64         }
  65         qemu_mutex_unlock(&pool_lock);
  66     }
  67
  68     qemu_coroutine_delete(co);
  69 }
  70
  71 static void __attribute__((constructor)) coroutine_pool_init(void)
  72 {
  73     qemu_mutex_init(&pool_lock);
  74 }
  75
  76 static void __attribute__((destructor)) coroutine_pool_cleanup(void)
  77 {
  78     Coroutine *co;
  79     Coroutine *tmp;
  80
  81     QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
  82         QSLIST_REMOVE_HEAD(&pool, pool_next);
  83         qemu_coroutine_delete(co);
  84     }
  85
  86     qemu_mutex_destroy(&pool_lock);
  87 }
  88
  89 static void coroutine_swap(Coroutine *from, Coroutine *to)
  90 {
  91     CoroutineAction ret;
  92
  93     ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD);
  94
  95     qemu_co_queue_run_restart(to);
  96
  97     switch (ret) {
  98     case COROUTINE_YIELD:
  99         return;
 100     case COROUTINE_TERMINATE:
 101         trace_qemu_coroutine_terminate(to);
 102         coroutine_delete(to);
 103         return;
 104     default:
 105         abort();
 106     }
 107 }
 108
 109 void qemu_coroutine_enter(Coroutine *co, void *opaque)
 110 {
 111     Coroutine *self = qemu_coroutine_self();
 112
 113     trace_qemu_coroutine_enter(self, co, opaque);
 114
 115     if (co->caller) {
 116         fprintf(stderr, "Co-routine re-entered recursively\n");
 117         abort();
 118     }
 119
 120     co->caller = self;
 121     co->entry_arg = opaque;
 122     coroutine_swap(self, co);
 123 }
 124
 125 void coroutine_fn qemu_coroutine_yield(void)
 126 {
 127     Coroutine *self = qemu_coroutine_self();
 128     Coroutine *to = self->caller;
 129
 130     trace_qemu_coroutine_yield(self, to);
 131
 132     if (!to) {
 133         fprintf(stderr, "Co-routine is yielding to no one\n");
 134         abort();
 135     }
 136
 137     self->caller = NULL;
 138     coroutine_swap(self, to);
 139 }