qemu

FORK: QEMU emulator
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qemu-coroutine-sleep.c (2133B)

      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 }