summaryrefslogtreecommitdiffstats
path: root/security/sandbox/chromium/base/threading/platform_thread.h
blob: e2b09bcb5bfd01f8d69346f5b9e262b712b9b6fc (plain)
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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// WARNING: You should *NOT* be using this class directly.  PlatformThread is
// the low-level platform-specific abstraction to the OS's threading interface.
// You should instead be using a message-loop driven Thread, see thread.h.

#ifndef BASE_THREADING_PLATFORM_THREAD_H_
#define BASE_THREADING_PLATFORM_THREAD_H_

#include <stddef.h>

#include "base/base_export.h"
#include "base/macros.h"
#include "base/time/time.h"
#include "build/build_config.h"

#if defined(OS_WIN)
#include <windows.h>
#elif defined(OS_POSIX)
#include <pthread.h>
#include <unistd.h>
#endif

namespace base {

// Used for logging. Always an integer value.
#if defined(OS_WIN)
typedef DWORD PlatformThreadId;
#elif defined(OS_POSIX)
typedef pid_t PlatformThreadId;
#endif

// Used for thread checking and debugging.
// Meant to be as fast as possible.
// These are produced by PlatformThread::CurrentRef(), and used to later
// check if we are on the same thread or not by using ==. These are safe
// to copy between threads, but can't be copied to another process as they
// have no meaning there. Also, the internal identifier can be re-used
// after a thread dies, so a PlatformThreadRef cannot be reliably used
// to distinguish a new thread from an old, dead thread.
class PlatformThreadRef {
 public:
#if defined(OS_WIN)
  typedef DWORD RefType;
#elif defined(OS_POSIX)
  typedef pthread_t RefType;
#endif
  PlatformThreadRef()
      : id_(0) {
  }

  explicit PlatformThreadRef(RefType id)
      : id_(id) {
  }

  bool operator==(PlatformThreadRef other) const {
    return id_ == other.id_;
  }

  bool is_null() const {
    return id_ == 0;
  }
 private:
  RefType id_;
};

// Used to operate on threads.
class PlatformThreadHandle {
 public:
#if defined(OS_WIN)
  typedef void* Handle;
#elif defined(OS_POSIX)
  typedef pthread_t Handle;
#endif

  PlatformThreadHandle() : handle_(0) {}

  explicit PlatformThreadHandle(Handle handle) : handle_(handle) {}

  bool is_equal(const PlatformThreadHandle& other) const {
    return handle_ == other.handle_;
  }

  bool is_null() const {
    return !handle_;
  }

  Handle platform_handle() const {
    return handle_;
  }

 private:
  Handle handle_;
};

const PlatformThreadId kInvalidThreadId(0);

// Valid values for priority of Thread::Options and SimpleThread::Options, and
// SetCurrentThreadPriority(), listed in increasing order of importance.
enum class ThreadPriority {
  // Suitable for threads that shouldn't disrupt high priority work.
  BACKGROUND,
  // Default priority level.
  NORMAL,
  // Suitable for threads which generate data for the display (at ~60Hz).
  DISPLAY,
  // Suitable for low-latency, glitch-resistant audio.
  REALTIME_AUDIO,
};

// A namespace for low-level thread functions.
class BASE_EXPORT PlatformThread {
 public:
  // Implement this interface to run code on a background thread.  Your
  // ThreadMain method will be called on the newly created thread.
  class BASE_EXPORT Delegate {
   public:
    virtual void ThreadMain() = 0;

   protected:
    virtual ~Delegate() {}
  };

  // Gets the current thread id, which may be useful for logging purposes.
  static PlatformThreadId CurrentId();

  // Gets the current thread reference, which can be used to check if
  // we're on the right thread quickly.
  static PlatformThreadRef CurrentRef();

  // Get the handle representing the current thread. On Windows, this is a
  // pseudo handle constant which will always represent the thread using it and
  // hence should not be shared with other threads nor be used to differentiate
  // the current thread from another.
  static PlatformThreadHandle CurrentHandle();

  // Yield the current thread so another thread can be scheduled.
  static void YieldCurrentThread();

  // Sleeps for the specified duration.
  static void Sleep(base::TimeDelta duration);

  // Sets the thread name visible to debuggers/tools. This has no effect
  // otherwise.
  static void SetName(const std::string& name);

  // Gets the thread name, if previously set by SetName.
  static const char* GetName();

  // Creates a new thread.  The |stack_size| parameter can be 0 to indicate
  // that the default stack size should be used.  Upon success,
  // |*thread_handle| will be assigned a handle to the newly created thread,
  // and |delegate|'s ThreadMain method will be executed on the newly created
  // thread.
  // NOTE: When you are done with the thread handle, you must call Join to
  // release system resources associated with the thread.  You must ensure that
  // the Delegate object outlives the thread.
  static bool Create(size_t stack_size,
                     Delegate* delegate,
                     PlatformThreadHandle* thread_handle) {
    return CreateWithPriority(stack_size, delegate, thread_handle,
                              ThreadPriority::NORMAL);
  }

  // CreateWithPriority() does the same thing as Create() except the priority of
  // the thread is set based on |priority|.
  static bool CreateWithPriority(size_t stack_size, Delegate* delegate,
                                 PlatformThreadHandle* thread_handle,
                                 ThreadPriority priority);

  // CreateNonJoinable() does the same thing as Create() except the thread
  // cannot be Join()'d.  Therefore, it also does not output a
  // PlatformThreadHandle.
  static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);

  // Joins with a thread created via the Create function.  This function blocks
  // the caller until the designated thread exits.  This will invalidate
  // |thread_handle|.
  static void Join(PlatformThreadHandle thread_handle);

  // Toggles the current thread's priority at runtime. A thread may not be able
  // to raise its priority back up after lowering it if the process does not
  // have a proper permission, e.g. CAP_SYS_NICE on Linux.
  // Since changing other threads' priority is not permitted in favor of
  // security, this interface is restricted to change only the current thread
  // priority (https://crbug.com/399473).
  static void SetCurrentThreadPriority(ThreadPriority priority);

  static ThreadPriority GetCurrentThreadPriority();

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
};

}  // namespace base

#endif  // BASE_THREADING_PLATFORM_THREAD_H_