util/coroutine-win32.c

   1 /*
   2  * Win32 coroutine initialization code
   3  *
   4  * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu/osdep.h"
  26 #include "qemu-common.h"
  27 #include "qemu/coroutine_int.h"
  28
  29 typedef struct
  30 {
  31     Coroutine base;
  32
  33     LPVOID fiber;
  34     CoroutineAction action;
  35 } CoroutineWin32;
  36
  37 static __thread CoroutineWin32 leader;
  38 static __thread Coroutine *current;
  39
  40 /* This function is marked noinline to prevent GCC from inlining it
  41  * into coroutine_trampoline(). If we allow it to do that then it
  42  * hoists the code to get the address of the TLS variable "current"
  43  * out of the while() loop. This is an invalid transformation because
  44  * the SwitchToFiber() call may be called when running thread A but
  45  * return in thread B, and so we might be in a different thread
  46  * context each time round the loop.
  47  */
  48 CoroutineAction __attribute__((noinline))
  49 qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
  50                       CoroutineAction action)
  51 {
  52     CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, from_);
  53     CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
  54
  55     current = to_;
  56
  57     to->action = action;
  58     SwitchToFiber(to->fiber);
  59     return from->action;
  60 }
  61
  62 static void CALLBACK coroutine_trampoline(void *co_)
  63 {
  64     Coroutine *co = co_;
  65
  66     while (true) {
  67         co->entry(co->entry_arg);
  68         qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
  69     }
  70 }
  71
  72 Coroutine *qemu_coroutine_new(void)
  73 {
  74     const size_t stack_size = 1 << 20;
  75     CoroutineWin32 *co;
  76
  77     co = g_malloc0(sizeof(*co));
  78     co->fiber = CreateFiber(stack_size, coroutine_trampoline, &co->base);
  79     return &co->base;
  80 }
  81
  82 void qemu_coroutine_delete(Coroutine *co_)
  83 {
  84     CoroutineWin32 *co = DO_UPCAST(CoroutineWin32, base, co_);
  85
  86     DeleteFiber(co->fiber);
  87     g_free(co);
  88 }
  89
  90 Coroutine *qemu_coroutine_self(void)
  91 {
  92     if (!current) {
  93         current = &leader.base;
  94         leader.fiber = ConvertThreadToFiber(NULL);
  95     }
  96     return current;
  97 }
  98
  99 bool qemu_in_coroutine(void)
 100 {
 101     return current && current->caller;
 102 }