1/*
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 <utils/Flattenable.h>
23#include <utils/RefBase.h>
24#include <utils/Timers.h>
25
26namespace android {
27
28class String8;
29
30// ===========================================================================
31// Fence
32// ===========================================================================
33
34class Fence
35    : public LightRefBase<Fence>, public Flattenable<Fence>
36{
37public:
38    static const sp<Fence> NO_FENCE;
39    static constexpr nsecs_t SIGNAL_TIME_PENDING = INT64_MAX;
40    static constexpr nsecs_t SIGNAL_TIME_INVALID = -1;
41    static inline bool isValidTimestamp(nsecs_t time) {
42        return time >= 0 && time < INT64_MAX;
43    }
44
45    // TIMEOUT_NEVER may be passed to the wait method to indicate that it
46    // should wait indefinitely for the fence to signal.
47    enum { TIMEOUT_NEVER = -1 };
48
49    // Construct a new Fence object with an invalid file descriptor.  This
50    // should be done when the Fence object will be set up by unflattening
51    // serialized data.
52    Fence();
53
54    // Construct a new Fence object to manage a given fence file descriptor.
55    // When the new Fence object is destructed the file descriptor will be
56    // closed.
57    explicit Fence(int fenceFd);
58
59    // Not copyable or movable.
60    Fence(const Fence& rhs) = delete;
61    Fence& operator=(const Fence& rhs) = delete;
62    Fence(Fence&& rhs) = delete;
63    Fence& operator=(Fence&& rhs) = delete;
64
65    // Check whether the Fence has an open fence file descriptor. Most Fence
66    // methods treat an invalid file descriptor just like a valid fence that
67    // is already signalled, so using this is usually not necessary.
68    bool isValid() const { return mFenceFd != -1; }
69
70    // wait waits for up to timeout milliseconds for the fence to signal.  If
71    // the fence signals then NO_ERROR is returned. If the timeout expires
72    // before the fence signals then -ETIME is returned.  A timeout of
73    // TIMEOUT_NEVER may be used to indicate that the call should wait
74    // indefinitely for the fence to signal.
75    status_t wait(int timeout);
76
77    // waitForever is a convenience function for waiting forever for a fence to
78    // signal (just like wait(TIMEOUT_NEVER)), but issuing an error to the
79    // system log and fence state to the kernel log if the wait lasts longer
80    // than a warning timeout.
81    // The logname argument should be a string identifying
82    // the caller and will be included in the log message.
83    status_t waitForever(const char* logname);
84
85    // merge combines two Fence objects, creating a new Fence object that
86    // becomes signaled when both f1 and f2 are signaled (even if f1 or f2 is
87    // destroyed before it becomes signaled).  The name argument specifies the
88    // human-readable name to associated with the new Fence object.
89    static sp<Fence> merge(const char* name, const sp<Fence>& f1,
90            const sp<Fence>& f2);
91
92    static sp<Fence> merge(const String8& name, const sp<Fence>& f1,
93            const sp<Fence>& f2);
94
95    // Return a duplicate of the fence file descriptor. The caller is
96    // responsible for closing the returned file descriptor. On error, -1 will
97    // be returned and errno will indicate the problem.
98    int dup() const;
99
100    // getSignalTime returns the system monotonic clock time at which the
101    // fence transitioned to the signaled state.  If the fence is not signaled
102    // then SIGNAL_TIME_PENDING is returned.  If the fence is invalid or if an
103    // error occurs then SIGNAL_TIME_INVALID is returned.
104    nsecs_t getSignalTime() const;
105
106    enum class Status {
107        Invalid,     // Fence is invalid
108        Unsignaled,  // Fence is valid but has not yet signaled
109        Signaled,    // Fence is valid and has signaled
110    };
111
112    // getStatus() returns whether the fence has signaled yet. Prefer this to
113    // getSignalTime() or wait() if all you care about is whether the fence has
114    // signaled.
115    inline Status getStatus() {
116        // The sync_wait call underlying wait() has been measured to be
117        // significantly faster than the sync_fence_info call underlying
118        // getSignalTime(), which might otherwise appear to be the more obvious
119        // way to check whether a fence has signaled.
120        switch (wait(0)) {
121            case NO_ERROR:
122                return Status::Signaled;
123            case -ETIME:
124                return Status::Unsignaled;
125            default:
126                return Status::Invalid;
127        }
128    }
129
130    // Flattenable interface
131    size_t getFlattenedSize() const;
132    size_t getFdCount() const;
133    status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
134    status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);
135
136private:
137    // Only allow instantiation using ref counting.
138    friend class LightRefBase<Fence>;
139    ~Fence();
140
141    int mFenceFd;
142};
143
144}; // namespace android
145
146#endif // ANDROID_FENCE_H
147