1781a6f09d9b0bc212842aee67c86b79cf2593e69Jiwen 'Steve' Cai/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_FENCE_H
18#define ANDROID_FENCE_H
19
20#include <stdint.h>
21
22#include <android-base/unique_fd.h>
23#include <utils/Flattenable.h>
24#include <utils/RefBase.h>
25#include <utils/Timers.h>
26
27namespace android {
28
29class String8;
30
31// ===========================================================================
32// Fence
33// ===========================================================================
34
35class Fence
36    : public LightRefBase<Fence>, public Flattenable<Fence>
37{
38public:
39    static const sp<Fence> NO_FENCE;
40    static constexpr nsecs_t SIGNAL_TIME_PENDING = INT64_MAX;
41    static constexpr nsecs_t SIGNAL_TIME_INVALID = -1;
42    static inline bool isValidTimestamp(nsecs_t time) {
43        return time >= 0 && time < INT64_MAX;
44    }
45
46    // TIMEOUT_NEVER may be passed to the wait method to indicate that it
47    // should wait indefinitely for the fence to signal.
48    enum { TIMEOUT_NEVER = -1 };
49
50    // Construct a new Fence object with an invalid file descriptor.  This
51    // should be done when the Fence object will be set up by unflattening
52    // serialized data.
53    Fence() = default;
54
55    // Construct a new Fence object to manage a given fence file descriptor.
56    // When the new Fence object is destructed the file descriptor will be
57    // closed.
58    explicit Fence(int fenceFd);
59    explicit Fence(base::unique_fd fenceFd);
60
61    // Not copyable or movable.
62    Fence(const Fence& rhs) = delete;
63    Fence& operator=(const Fence& rhs) = delete;
64    Fence(Fence&& rhs) = delete;
65    Fence& operator=(Fence&& rhs) = delete;
66
67    // Check whether the Fence has an open fence file descriptor. Most Fence
68    // methods treat an invalid file descriptor just like a valid fence that
69    // is already signalled, so using this is usually not necessary.
70    bool isValid() const { return mFenceFd != -1; }
71
72    // wait waits for up to timeout milliseconds for the fence to signal.  If
73    // the fence signals then NO_ERROR is returned. If the timeout expires
74    // before the fence signals then -ETIME is returned.  A timeout of
75    // TIMEOUT_NEVER may be used to indicate that the call should wait
76    // indefinitely for the fence to signal.
77    status_t wait(int timeout);
78
79    // waitForever is a convenience function for waiting forever for a fence to
80    // signal (just like wait(TIMEOUT_NEVER)), but issuing an error to the
81    // system log and fence state to the kernel log if the wait lasts longer
82    // than a warning timeout.
83    // The logname argument should be a string identifying
84    // the caller and will be included in the log message.
85    status_t waitForever(const char* logname);
86
87    // merge combines two Fence objects, creating a new Fence object that
88    // becomes signaled when both f1 and f2 are signaled (even if f1 or f2 is
89    // destroyed before it becomes signaled).  The name argument specifies the
90    // human-readable name to associated with the new Fence object.
91    static sp<Fence> merge(const char* name, const sp<Fence>& f1,
92            const sp<Fence>& f2);
93
94    static sp<Fence> merge(const String8& name, const sp<Fence>& f1,
95            const sp<Fence>& f2);
96
97    // Return a duplicate of the fence file descriptor. The caller is
98    // responsible for closing the returned file descriptor. On error, -1 will
99    // be returned and errno will indicate the problem.
100    int dup() const;
101
102    // getSignalTime returns the system monotonic clock time at which the
103    // fence transitioned to the signaled state.  If the fence is not signaled
104    // then SIGNAL_TIME_PENDING is returned.  If the fence is invalid or if an
105    // error occurs then SIGNAL_TIME_INVALID is returned.
106    nsecs_t getSignalTime() const;
107
108    enum class Status {
109        Invalid,     // Fence is invalid
110        Unsignaled,  // Fence is valid but has not yet signaled
111        Signaled,    // Fence is valid and has signaled
112    };
113
114    // getStatus() returns whether the fence has signaled yet. Prefer this to
115    // getSignalTime() or wait() if all you care about is whether the fence has
116    // signaled.
117    inline Status getStatus() {
118        // The sync_wait call underlying wait() has been measured to be
119        // significantly faster than the sync_fence_info call underlying
120        // getSignalTime(), which might otherwise appear to be the more obvious
121        // way to check whether a fence has signaled.
122        switch (wait(0)) {
123            case NO_ERROR:
124                return Status::Signaled;
125            case -ETIME:
126                return Status::Unsignaled;
127            default:
128                return Status::Invalid;
129        }
130    }
131
132    // Flattenable interface
133    size_t getFlattenedSize() const;
134    size_t getFdCount() const;
135    status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
136    status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);
137
138private:
139    // Only allow instantiation using ref counting.
140    friend class LightRefBase<Fence>;
141    ~Fence() = default;
142
143    base::unique_fd mFenceFd;
144};
145
146}; // namespace android
147
148#endif // ANDROID_FENCE_H
149