xref: /openbmc/qemu/util/coroutine-windows.c (revision 6739825a)
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/coroutine_int.h"
27 #include "qemu/coroutine-tls.h"
28 
29 typedef struct
30 {
31     Coroutine base;
32 
33     LPVOID fiber;
34     CoroutineAction action;
35 } CoroutineWin32;
36 
37 QEMU_DEFINE_STATIC_CO_TLS(CoroutineWin32, leader);
38 QEMU_DEFINE_STATIC_CO_TLS(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))
qemu_coroutine_switch(Coroutine * from_,Coroutine * to_,CoroutineAction action)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     set_current(to_);
56 
57     to->action = action;
58     SwitchToFiber(to->fiber);
59     return from->action;
60 }
61 
coroutine_trampoline(void * co_)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 
qemu_coroutine_new(void)72 Coroutine *qemu_coroutine_new(void)
73 {
74     const size_t stack_size = COROUTINE_STACK_SIZE;
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 
qemu_coroutine_delete(Coroutine * co_)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 
qemu_coroutine_self(void)90 Coroutine *qemu_coroutine_self(void)
91 {
92     Coroutine *current = get_current();
93 
94     if (!current) {
95         CoroutineWin32 *leader = get_ptr_leader();
96 
97         current = &leader->base;
98         set_current(current);
99         leader->fiber = ConvertThreadToFiber(NULL);
100     }
101     return current;
102 }
103 
qemu_in_coroutine(void)104 bool qemu_in_coroutine(void)
105 {
106     Coroutine *current = get_current();
107 
108     return current && current->caller;
109 }
110