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 struct QemuCoSleepState {
  23     Coroutine *co;
  24     QEMUTimer *ts;
  25     QemuCoSleepState **user_state_pointer;
  26 };
  27
  28 void qemu_co_sleep_wake(QemuCoSleepState *sleep_state)
  29 {
  30     /* Write of schedule protected by barrier write in aio_co_schedule */
  31     const char *scheduled = atomic_cmpxchg(&sleep_state->co->scheduled,
  32                                            qemu_co_sleep_ns__scheduled, NULL);
  33
  34     assert(scheduled == qemu_co_sleep_ns__scheduled);
  35     if (sleep_state->user_state_pointer) {
  36         *sleep_state->user_state_pointer = NULL;
  37     }
  38     timer_del(sleep_state->ts);
  39     aio_co_wake(sleep_state->co);
  40 }
  41
  42 static void co_sleep_cb(void *opaque)
  43 {
  44     qemu_co_sleep_wake(opaque);
  45 }
  46
  47 void coroutine_fn qemu_co_sleep_ns_wakeable(QEMUClockType type, int64_t ns,
  48                                             QemuCoSleepState **sleep_state)
  49 {
  50     AioContext *ctx = qemu_get_current_aio_context();
  51     QemuCoSleepState state = {
  52         .co = qemu_coroutine_self(),
  53         .ts = aio_timer_new(ctx, type, SCALE_NS, co_sleep_cb, &state),
  54         .user_state_pointer = sleep_state,
  55     };
  56
  57     const char *scheduled = atomic_cmpxchg(&state.co->scheduled, NULL,
  58                                            qemu_co_sleep_ns__scheduled);
  59     if (scheduled) {
  60         fprintf(stderr,
  61                 "%s: Co-routine was already scheduled in '%s'\n",
  62                 __func__, scheduled);
  63         abort();
  64     }
  65
  66     if (sleep_state) {
  67         *sleep_state = &state;
  68     }
  69     timer_mod(state.ts, qemu_clock_get_ns(type) + ns);
  70     qemu_coroutine_yield();
  71     if (sleep_state) {
  72         /*
  73          * Note that *sleep_state is cleared during qemu_co_sleep_wake
  74          * before resuming this coroutine.
  75          */
  76         assert(*sleep_state == NULL);
  77     }
  78     timer_free(state.ts);
  79 }