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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef BASE_THREADING_THREAD_RESTRICTIONS_H_ | 5 #ifndef BASE_THREADING_THREAD_RESTRICTIONS_H_ |
6 #define BASE_THREADING_THREAD_RESTRICTIONS_H_ | 6 #define BASE_THREADING_THREAD_RESTRICTIONS_H_ |
7 | 7 |
8 #include "base/base_api.h" | 8 #include "base/base_export.h" |
9 #include "base/basictypes.h" | 9 #include "base/basictypes.h" |
10 | 10 |
11 namespace base { | 11 namespace base { |
12 | 12 |
13 // Certain behavior is disallowed on certain threads. ThreadRestrictions helps | 13 // Certain behavior is disallowed on certain threads. ThreadRestrictions helps |
14 // enforce these rules. Examples of such rules: | 14 // enforce these rules. Examples of such rules: |
15 // | 15 // |
16 // * Do not do blocking IO (makes the thread janky) | 16 // * Do not do blocking IO (makes the thread janky) |
17 // * Do not access Singleton/LazyInstance (may lead to shutdown crashes) | 17 // * Do not access Singleton/LazyInstance (may lead to shutdown crashes) |
18 // | 18 // |
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29 // | 29 // |
30 // ThreadRestrictions does nothing in release builds; it is debug-only. | 30 // ThreadRestrictions does nothing in release builds; it is debug-only. |
31 // | 31 // |
32 // Style tip: where should you put AssertIOAllowed checks? It's best | 32 // Style tip: where should you put AssertIOAllowed checks? It's best |
33 // if you put them as close to the disk access as possible, at the | 33 // if you put them as close to the disk access as possible, at the |
34 // lowest level. This rule is simple to follow and helps catch all | 34 // lowest level. This rule is simple to follow and helps catch all |
35 // callers. For example, if your function GoDoSomeBlockingDiskCall() | 35 // callers. For example, if your function GoDoSomeBlockingDiskCall() |
36 // only calls other functions in Chrome and not fopen(), you should go | 36 // only calls other functions in Chrome and not fopen(), you should go |
37 // add the AssertIOAllowed checks in the helper functions. | 37 // add the AssertIOAllowed checks in the helper functions. |
38 | 38 |
39 class BASE_API ThreadRestrictions { | 39 class BASE_EXPORT ThreadRestrictions { |
40 public: | 40 public: |
41 // Constructing a ScopedAllowIO temporarily allows IO for the current | 41 // Constructing a ScopedAllowIO temporarily allows IO for the current |
42 // thread. Doing this is almost certainly always incorrect. | 42 // thread. Doing this is almost certainly always incorrect. |
43 class BASE_API ScopedAllowIO { | 43 class BASE_EXPORT ScopedAllowIO { |
44 public: | 44 public: |
45 ScopedAllowIO() { previous_value_ = SetIOAllowed(true); } | 45 ScopedAllowIO() { previous_value_ = SetIOAllowed(true); } |
46 ~ScopedAllowIO() { SetIOAllowed(previous_value_); } | 46 ~ScopedAllowIO() { SetIOAllowed(previous_value_); } |
47 private: | 47 private: |
48 // Whether IO is allowed when the ScopedAllowIO was constructed. | 48 // Whether IO is allowed when the ScopedAllowIO was constructed. |
49 bool previous_value_; | 49 bool previous_value_; |
50 | 50 |
51 DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO); | 51 DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO); |
52 }; | 52 }; |
53 | 53 |
54 // Constructing a ScopedAllowSingleton temporarily allows accessing for the | 54 // Constructing a ScopedAllowSingleton temporarily allows accessing for the |
55 // current thread. Doing this is almost always incorrect. | 55 // current thread. Doing this is almost always incorrect. |
56 class BASE_API ScopedAllowSingleton { | 56 class BASE_EXPORT ScopedAllowSingleton { |
57 public: | 57 public: |
58 ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); } | 58 ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); } |
59 ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); } | 59 ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); } |
60 private: | 60 private: |
61 // Whether singleton use is allowed when the ScopedAllowSingleton was | 61 // Whether singleton use is allowed when the ScopedAllowSingleton was |
62 // constructed. | 62 // constructed. |
63 bool previous_value_; | 63 bool previous_value_; |
64 | 64 |
65 DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton); | 65 DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton); |
66 }; | 66 }; |
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92 static void AssertSingletonAllowed() {} | 92 static void AssertSingletonAllowed() {} |
93 #endif | 93 #endif |
94 | 94 |
95 private: | 95 private: |
96 DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions); | 96 DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions); |
97 }; | 97 }; |
98 | 98 |
99 } // namespace base | 99 } // namespace base |
100 | 100 |
101 #endif // BASE_THREADING_THREAD_RESTRICTIONS_H_ | 101 #endif // BASE_THREADING_THREAD_RESTRICTIONS_H_ |
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