1 // Copyright 2019 The Marl Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 // Minimal assembly implementations of fiber context switching for Unix-based
16 // platforms.
17 //
18 // Note: Unlike makecontext, swapcontext or the Windows fiber APIs, these
19 // assembly implementations *do not* save or restore signal masks,
20 // floating-point control or status registers, FS and GS segment registers,
21 // thread-local storage state nor any SIMD registers. This should not be a
22 // problem as the marl scheduler requires fibers to be executed on the same
23 // thread throughout their lifetime.
24
25 #if defined(__x86_64__)
26 #include "osfiber_asm_x64.h"
27 #elif defined(__i386__)
28 #include "osfiber_asm_x86.h"
29 #elif defined(__aarch64__)
30 #include "osfiber_asm_aarch64.h"
31 #elif defined(__arm__)
32 #include "osfiber_asm_arm.h"
33 #elif defined(__powerpc64__)
34 #include "osfiber_asm_ppc64.h"
35 #elif defined(__mips__) && _MIPS_SIM == _ABI64
36 #include "osfiber_asm_mips64.h"
37 #elif defined(__riscv) && __riscv_xlen == 64
38 #include "osfiber_asm_rv64.h"
39 #elif defined(__loongarch__) && _LOONGARCH_SIM == _ABILP64
40 #include "osfiber_asm_loongarch64.h"
41 #else
42 #error "Unsupported target"
43 #endif
44
45 #include "marl/export.h"
46 #include "marl/memory.h"
47
48 #include <functional>
49 #include <memory>
50
51 extern "C" {
52
53 MARL_EXPORT
54 extern void marl_fiber_set_target(marl_fiber_context*,
55 void* stack,
56 uint32_t stack_size,
57 void (*target)(void*),
58 void* arg);
59 MARL_EXPORT
60 extern void marl_fiber_swap(marl_fiber_context* from,
61 const marl_fiber_context* to);
62
63 } // extern "C"
64
65 namespace marl {
66
67 class OSFiber {
68 public:
69 inline OSFiber(Allocator*);
70 inline ~OSFiber();
71
72 // createFiberFromCurrentThread() returns a fiber created from the current
73 // thread.
74 MARL_NO_EXPORT static inline Allocator::unique_ptr<OSFiber>
75 createFiberFromCurrentThread(Allocator* allocator);
76
77 // createFiber() returns a new fiber with the given stack size that will
78 // call func when switched to. func() must end by switching back to another
79 // fiber, and must not return.
80 MARL_NO_EXPORT static inline Allocator::unique_ptr<OSFiber> createFiber(
81 Allocator* allocator,
82 size_t stackSize,
83 const std::function<void()>& func);
84
85 // switchTo() immediately switches execution to the given fiber.
86 // switchTo() must be called on the currently executing fiber.
87 MARL_NO_EXPORT inline void switchTo(OSFiber*);
88
89 private:
90 MARL_NO_EXPORT
91 static inline void run(OSFiber* self);
92
93 Allocator* allocator;
94 marl_fiber_context context;
95 std::function<void()> target;
96 Allocation stack;
97 };
98
OSFiber(Allocator * allocator)99 OSFiber::OSFiber(Allocator* allocator) : allocator(allocator) {}
100
~OSFiber()101 OSFiber::~OSFiber() {
102 if (stack.ptr != nullptr) {
103 allocator->free(stack);
104 }
105 }
106
createFiberFromCurrentThread(Allocator * allocator)107 Allocator::unique_ptr<OSFiber> OSFiber::createFiberFromCurrentThread(
108 Allocator* allocator) {
109 auto out = allocator->make_unique<OSFiber>(allocator);
110 out->context = {};
111 return out;
112 }
113
createFiber(Allocator * allocator,size_t stackSize,const std::function<void ()> & func)114 Allocator::unique_ptr<OSFiber> OSFiber::createFiber(
115 Allocator* allocator,
116 size_t stackSize,
117 const std::function<void()>& func) {
118 Allocation::Request request;
119 request.size = stackSize;
120 request.alignment = 16;
121 request.usage = Allocation::Usage::Stack;
122 #if MARL_USE_FIBER_STACK_GUARDS
123 request.useGuards = true;
124 #endif
125
126 auto out = allocator->make_unique<OSFiber>(allocator);
127 out->context = {};
128 out->target = func;
129 out->stack = allocator->allocate(request);
130 marl_fiber_set_target(
131 &out->context, out->stack.ptr, static_cast<uint32_t>(stackSize),
132 reinterpret_cast<void (*)(void*)>(&OSFiber::run), out.get());
133 return out;
134 }
135
run(OSFiber * self)136 void OSFiber::run(OSFiber* self) {
137 self->target();
138 }
139
switchTo(OSFiber * fiber)140 void OSFiber::switchTo(OSFiber* fiber) {
141 marl_fiber_swap(&context, &fiber->context);
142 }
143
144 } // namespace marl
145