1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <map>
#include <utility>
#include <vector>
#include <boost/range/algorithm_ext/erase.hpp>
#include "common/assert.h"
#include "core/core.h"
#include "core/hle/kernel/errors.h"
#include "core/hle/kernel/handle_table.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/mutex.h"
#include "core/hle/kernel/thread.h"
#include "core/hle/result.h"
namespace Kernel {
/// Returns the number of threads that are waiting for a mutex, and the highest priority one among
/// those.
static std::pair<SharedPtr<Thread>, u32> GetHighestPriorityMutexWaitingThread(
const SharedPtr<Thread>& current_thread, VAddr mutex_addr) {
SharedPtr<Thread> highest_priority_thread;
u32 num_waiters = 0;
for (auto& thread : current_thread->wait_mutex_threads) {
if (thread->mutex_wait_address != mutex_addr)
continue;
ASSERT(thread->status == ThreadStatus::WaitMutex);
++num_waiters;
if (highest_priority_thread == nullptr ||
thread->GetPriority() < highest_priority_thread->GetPriority()) {
highest_priority_thread = thread;
}
}
return {highest_priority_thread, num_waiters};
}
/// Update the mutex owner field of all threads waiting on the mutex to point to the new owner.
static void TransferMutexOwnership(VAddr mutex_addr, SharedPtr<Thread> current_thread,
SharedPtr<Thread> new_owner) {
auto threads = current_thread->wait_mutex_threads;
for (auto& thread : threads) {
if (thread->mutex_wait_address != mutex_addr)
continue;
ASSERT(thread->lock_owner == current_thread);
current_thread->RemoveMutexWaiter(thread);
if (new_owner != thread)
new_owner->AddMutexWaiter(thread);
}
}
ResultCode Mutex::TryAcquire(VAddr address, Handle holding_thread_handle,
Handle requesting_thread_handle) {
// The mutex address must be 4-byte aligned
if ((address % sizeof(u32)) != 0) {
return ResultCode(ErrorModule::Kernel, ErrCodes::InvalidAddress);
}
SharedPtr<Thread> holding_thread = g_handle_table.Get<Thread>(holding_thread_handle);
SharedPtr<Thread> requesting_thread = g_handle_table.Get<Thread>(requesting_thread_handle);
// TODO(Subv): It is currently unknown if it is possible to lock a mutex in behalf of another
// thread.
ASSERT(requesting_thread == GetCurrentThread());
u32 addr_value = Memory::Read32(address);
// If the mutex isn't being held, just return success.
if (addr_value != (holding_thread_handle | Mutex::MutexHasWaitersFlag)) {
return RESULT_SUCCESS;
}
if (holding_thread == nullptr)
return ERR_INVALID_HANDLE;
// Wait until the mutex is released
GetCurrentThread()->mutex_wait_address = address;
GetCurrentThread()->wait_handle = requesting_thread_handle;
GetCurrentThread()->status = ThreadStatus::WaitMutex;
GetCurrentThread()->wakeup_callback = nullptr;
// Update the lock holder thread's priority to prevent priority inversion.
holding_thread->AddMutexWaiter(GetCurrentThread());
Core::System::GetInstance().PrepareReschedule();
return RESULT_SUCCESS;
}
ResultCode Mutex::Release(VAddr address) {
// The mutex address must be 4-byte aligned
if ((address % sizeof(u32)) != 0) {
return ResultCode(ErrorModule::Kernel, ErrCodes::InvalidAddress);
}
auto [thread, num_waiters] = GetHighestPriorityMutexWaitingThread(GetCurrentThread(), address);
// There are no more threads waiting for the mutex, release it completely.
if (thread == nullptr) {
Memory::Write32(address, 0);
return RESULT_SUCCESS;
}
// Transfer the ownership of the mutex from the previous owner to the new one.
TransferMutexOwnership(address, GetCurrentThread(), thread);
u32 mutex_value = thread->wait_handle;
if (num_waiters >= 2) {
// Notify the guest that there are still some threads waiting for the mutex
mutex_value |= Mutex::MutexHasWaitersFlag;
}
// Grant the mutex to the next waiting thread and resume it.
Memory::Write32(address, mutex_value);
ASSERT(thread->status == ThreadStatus::WaitMutex);
thread->ResumeFromWait();
thread->lock_owner = nullptr;
thread->condvar_wait_address = 0;
thread->mutex_wait_address = 0;
thread->wait_handle = 0;
return RESULT_SUCCESS;
}
} // namespace Kernel
|
