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-common.h"
  26 #include "qemu/coroutine_int.h"
  27
  28 typedef struct
  29 {
  30     Coroutine base;
  31
  32     LPVOID fiber;
  33     CoroutineAction action;
  34 } CoroutineWin32;
  35
  36 static __thread CoroutineWin32 leader;
  37 static __thread Coroutine *current;
  38
  39 /* This function is marked noinline to prevent GCC from inlining it
  40  * into coroutine_trampoline(). If we allow it to do that then it
  41  * hoists the code to get the address of the TLS variable "current"
  42  * out of the while() loop. This is an invalid transformation because
  43  * the SwitchToFiber() call may be called when running thread A but
  44  * return in thread B, and so we might be in a different thread
  45  * context each time round the loop.
  46  */
  47 CoroutineAction __attribute__((noinline))
  48 qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
  49                       CoroutineAction action)
  50 {
  51     CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, from_);
  52     CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
  53
  54     current = to_;
  55
  56     to->action = action;
  57     SwitchToFiber(to->fiber);
  58     return from->action;
  59 }
  60
  61 static void CALLBACK coroutine_trampoline(void *co_)
  62 {
  63     Coroutine *co = co_;
  64
  65     while (true) {
  66         co->entry(co->entry_arg);
  67         qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
  68     }
  69 }
  70
  71 Coroutine *qemu_coroutine_new(void)
  72 {
  73     const size_t stack_size = 1 << 20;
  74     CoroutineWin32 *co;
  75
  76     co = g_malloc0(sizeof(*co));
  77     co->fiber = CreateFiber(stack_size, coroutine_trampoline, &co->base);
  78     return &co->base;
  79 }
  80
  81 void qemu_coroutine_delete(Coroutine *co_)
  82 {
  83     CoroutineWin32 *co = DO_UPCAST(CoroutineWin32, base, co_);
  84
  85     DeleteFiber(co->fiber);
  86     g_free(co);
  87 }
  88
  89 Coroutine *qemu_coroutine_self(void)
  90 {
  91     if (!current) {
  92         current = &leader.base;
  93         leader.fiber = ConvertThreadToFiber(NULL);
  94     }
  95     return current;
  96 }
  97
  98 bool qemu_in_coroutine(void)
  99 {
 100     return current && current->caller;
 101 }