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_int.h"
  16 #include "qemu/timer.h"
  17 #include "block/aio.h"
  18
  19 static const char *qemu_co_sleep_ns__scheduled = "qemu_co_sleep_ns";
  20
  21 void qemu_co_sleep_wake(QemuCoSleep *w)
  22 {
  23     Coroutine *co;
  24
  25     co = w->to_wake;
  26     w->to_wake = NULL;
  27     if (co) {
  28         /* Write of schedule protected by barrier write in aio_co_schedule */
  29         const char *scheduled = qatomic_cmpxchg(&co->scheduled,
  30                                                 qemu_co_sleep_ns__scheduled, NULL);
  31
  32         assert(scheduled == qemu_co_sleep_ns__scheduled);
  33         aio_co_wake(co);
  34     }
  35 }
  36
  37 static void co_sleep_cb(void *opaque)
  38 {
  39     QemuCoSleep *w = opaque;
  40     qemu_co_sleep_wake(w);
  41 }
  42
  43 void coroutine_fn qemu_co_sleep(QemuCoSleep *w)
  44 {
  45     Coroutine *co = qemu_coroutine_self();
  46
  47     const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL,
  48                                             qemu_co_sleep_ns__scheduled);
  49     if (scheduled) {
  50         fprintf(stderr,
  51                 "%s: Co-routine was already scheduled in '%s'\n",
  52                 __func__, scheduled);
  53         abort();
  54     }
  55
  56     w->to_wake = co;
  57     qemu_coroutine_yield();
  58
  59     /* w->to_wake is cleared before resuming this coroutine.  */
  60     assert(w->to_wake == NULL);
  61 }
  62
  63 void coroutine_fn qemu_co_sleep_ns_wakeable(QemuCoSleep *w,
  64                                             QEMUClockType type, int64_t ns)
  65 {
  66     AioContext *ctx = qemu_get_current_aio_context();
  67     QEMUTimer ts;
  68
  69     aio_timer_init(ctx, &ts, type, SCALE_NS, co_sleep_cb, w);
  70     timer_mod(&ts, qemu_clock_get_ns(type) + ns);
  71
  72     /*
  73      * The timer will fire in the current AiOContext, so the callback
  74      * must happen after qemu_co_sleep yields and there is no race
  75      * between timer_mod and qemu_co_sleep.
  76      */
  77     qemu_co_sleep(w);
  78     timer_del(&ts);
  79 }