ahci: unify sglist preparation
[qemu.git] / 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 "block/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 }