LXR qemu/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
  20static const char *qemu_co_sleep_ns__scheduled = "qemu_co_sleep_ns";
  21
  22void 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
  38static void co_sleep_cb(void *opaque)
  39{
  40    QemuCoSleep *w = opaque;
  41    qemu_co_sleep_wake(w);
  42}
  43
  44void 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
  64void 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}
  81