util/qemu-coroutine-sleep.c

   1 /*
   2  * QEMU coroutine sleep
   3  *
   4  * Copyright IBM, Corp. 2011
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qemu/coroutine.h"
  16 #include "qemu/coroutine_int.h"
  17 #include "qemu/timer.h"
  18 #include "block/aio.h"
  19
  20 static const char *qemu_co_sleep_ns__scheduled = "qemu_co_sleep_ns";
  21
  22 void qemu_co_sleep_wake(QemuCoSleep *w)
  23 {
  24     Coroutine *co;
  25
  26     co = w->to_wake;
  27     w->to_wake = NULL;
  28     if (co) {
  29         /* Write of schedule protected by barrier write in aio_co_schedule */
  30         const char *scheduled = qatomic_cmpxchg(&co->scheduled,
  31                                                 qemu_co_sleep_ns__scheduled, NULL);
  32
  33         assert(scheduled == qemu_co_sleep_ns__scheduled);
  34         aio_co_wake(co);
  35     }
  36 }
  37
  38 static void co_sleep_cb(void *opaque)
  39 {
  40     QemuCoSleep *w = opaque;
  41     qemu_co_sleep_wake(w);
  42 }
  43
  44 void coroutine_fn qemu_co_sleep(QemuCoSleep *w)
  45 {
  46     Coroutine *co = qemu_coroutine_self();
  47
  48     const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL,
  49                                             qemu_co_sleep_ns__scheduled);
  50     if (scheduled) {
  51         fprintf(stderr,
  52                 "%s: Co-routine was already scheduled in '%s'\n",
  53                 __func__, scheduled);
  54         abort();
  55     }
  56
  57     w->to_wake = co;
  58     qemu_coroutine_yield();
  59
  60     /* w->to_wake is cleared before resuming this coroutine.  */
  61     assert(w->to_wake == NULL);
  62 }
  63
  64 void coroutine_fn qemu_co_sleep_ns_wakeable(QemuCoSleep *w,
  65                                             QEMUClockType type, int64_t ns)
  66 {
  67     AioContext *ctx = qemu_get_current_aio_context();
  68     QEMUTimer ts;
  69
  70     aio_timer_init(ctx, &ts, type, SCALE_NS, co_sleep_cb, w);
  71     timer_mod(&ts, qemu_clock_get_ns(type) + ns);
  72
  73     /*
  74      * The timer will fire in the current AiOContext, so the callback
  75      * must happen after qemu_co_sleep yields and there is no race
  76      * between timer_mod and qemu_co_sleep.
  77      */
  78     qemu_co_sleep(w);
  79     timer_del(&ts);
  80 }