1*9356374aSAndroid Build Coastguard Worker // Copyright 2017 The Abseil Authors. 2*9356374aSAndroid Build Coastguard Worker // 3*9356374aSAndroid Build Coastguard Worker // Licensed under the Apache License, Version 2.0 (the "License"); 4*9356374aSAndroid Build Coastguard Worker // you may not use this file except in compliance with the License. 5*9356374aSAndroid Build Coastguard Worker // You may obtain a copy of the License at 6*9356374aSAndroid Build Coastguard Worker // 7*9356374aSAndroid Build Coastguard Worker // https://www.apache.org/licenses/LICENSE-2.0 8*9356374aSAndroid Build Coastguard Worker // 9*9356374aSAndroid Build Coastguard Worker // Unless required by applicable law or agreed to in writing, software 10*9356374aSAndroid Build Coastguard Worker // distributed under the License is distributed on an "AS IS" BASIS, 11*9356374aSAndroid Build Coastguard Worker // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12*9356374aSAndroid Build Coastguard Worker // See the License for the specific language governing permissions and 13*9356374aSAndroid Build Coastguard Worker // limitations under the License. 14*9356374aSAndroid Build Coastguard Worker 15*9356374aSAndroid Build Coastguard Worker #ifndef ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ 16*9356374aSAndroid Build Coastguard Worker #define ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ 17*9356374aSAndroid Build Coastguard Worker 18*9356374aSAndroid Build Coastguard Worker #ifndef _WIN32 19*9356374aSAndroid Build Coastguard Worker #include <sys/types.h> 20*9356374aSAndroid Build Coastguard Worker #endif 21*9356374aSAndroid Build Coastguard Worker 22*9356374aSAndroid Build Coastguard Worker #include <algorithm> 23*9356374aSAndroid Build Coastguard Worker #include <chrono> // NOLINT(build/c++11) 24*9356374aSAndroid Build Coastguard Worker #include <cstdint> 25*9356374aSAndroid Build Coastguard Worker #include <ctime> 26*9356374aSAndroid Build Coastguard Worker #include <limits> 27*9356374aSAndroid Build Coastguard Worker 28*9356374aSAndroid Build Coastguard Worker #include "absl/base/config.h" 29*9356374aSAndroid Build Coastguard Worker #include "absl/base/internal/raw_logging.h" 30*9356374aSAndroid Build Coastguard Worker #include "absl/time/clock.h" 31*9356374aSAndroid Build Coastguard Worker #include "absl/time/time.h" 32*9356374aSAndroid Build Coastguard Worker 33*9356374aSAndroid Build Coastguard Worker namespace absl { 34*9356374aSAndroid Build Coastguard Worker ABSL_NAMESPACE_BEGIN 35*9356374aSAndroid Build Coastguard Worker namespace synchronization_internal { 36*9356374aSAndroid Build Coastguard Worker 37*9356374aSAndroid Build Coastguard Worker // An optional timeout, with nanosecond granularity. 38*9356374aSAndroid Build Coastguard Worker // 39*9356374aSAndroid Build Coastguard Worker // This is a private low-level API for use by a handful of low-level 40*9356374aSAndroid Build Coastguard Worker // components. Higher-level components should build APIs based on 41*9356374aSAndroid Build Coastguard Worker // absl::Time and absl::Duration. 42*9356374aSAndroid Build Coastguard Worker class KernelTimeout { 43*9356374aSAndroid Build Coastguard Worker public: 44*9356374aSAndroid Build Coastguard Worker // Construct an absolute timeout that should expire at `t`. 45*9356374aSAndroid Build Coastguard Worker explicit KernelTimeout(absl::Time t); 46*9356374aSAndroid Build Coastguard Worker 47*9356374aSAndroid Build Coastguard Worker // Construct a relative timeout that should expire after `d`. 48*9356374aSAndroid Build Coastguard Worker explicit KernelTimeout(absl::Duration d); 49*9356374aSAndroid Build Coastguard Worker 50*9356374aSAndroid Build Coastguard Worker // Infinite timeout. KernelTimeout()51*9356374aSAndroid Build Coastguard Worker constexpr KernelTimeout() : rep_(kNoTimeout) {} 52*9356374aSAndroid Build Coastguard Worker 53*9356374aSAndroid Build Coastguard Worker // A more explicit factory for those who prefer it. 54*9356374aSAndroid Build Coastguard Worker // Equivalent to `KernelTimeout()`. Never()55*9356374aSAndroid Build Coastguard Worker static constexpr KernelTimeout Never() { return KernelTimeout(); } 56*9356374aSAndroid Build Coastguard Worker 57*9356374aSAndroid Build Coastguard Worker // Returns true if there is a timeout that will eventually expire. 58*9356374aSAndroid Build Coastguard Worker // Returns false if the timeout is infinite. has_timeout()59*9356374aSAndroid Build Coastguard Worker bool has_timeout() const { return rep_ != kNoTimeout; } 60*9356374aSAndroid Build Coastguard Worker 61*9356374aSAndroid Build Coastguard Worker // If `has_timeout()` is true, returns true if the timeout was provided as an 62*9356374aSAndroid Build Coastguard Worker // `absl::Time`. The return value is undefined if `has_timeout()` is false 63*9356374aSAndroid Build Coastguard Worker // because all indefinite timeouts are equivalent. is_absolute_timeout()64*9356374aSAndroid Build Coastguard Worker bool is_absolute_timeout() const { return (rep_ & 1) == 0; } 65*9356374aSAndroid Build Coastguard Worker 66*9356374aSAndroid Build Coastguard Worker // If `has_timeout()` is true, returns true if the timeout was provided as an 67*9356374aSAndroid Build Coastguard Worker // `absl::Duration`. The return value is undefined if `has_timeout()` is false 68*9356374aSAndroid Build Coastguard Worker // because all indefinite timeouts are equivalent. is_relative_timeout()69*9356374aSAndroid Build Coastguard Worker bool is_relative_timeout() const { return (rep_ & 1) == 1; } 70*9356374aSAndroid Build Coastguard Worker 71*9356374aSAndroid Build Coastguard Worker // Convert to `struct timespec` for interfaces that expect an absolute 72*9356374aSAndroid Build Coastguard Worker // timeout. If !has_timeout() or is_relative_timeout(), attempts to convert to 73*9356374aSAndroid Build Coastguard Worker // a reasonable absolute timeout, but callers should to test has_timeout() and 74*9356374aSAndroid Build Coastguard Worker // is_relative_timeout() and prefer to use a more appropriate interface. 75*9356374aSAndroid Build Coastguard Worker struct timespec MakeAbsTimespec() const; 76*9356374aSAndroid Build Coastguard Worker 77*9356374aSAndroid Build Coastguard Worker // Convert to `struct timespec` for interfaces that expect a relative 78*9356374aSAndroid Build Coastguard Worker // timeout. If !has_timeout() or is_absolute_timeout(), attempts to convert to 79*9356374aSAndroid Build Coastguard Worker // a reasonable relative timeout, but callers should to test has_timeout() and 80*9356374aSAndroid Build Coastguard Worker // is_absolute_timeout() and prefer to use a more appropriate interface. Since 81*9356374aSAndroid Build Coastguard Worker // the return value is a relative duration, it should be recomputed by calling 82*9356374aSAndroid Build Coastguard Worker // this method in the case of a spurious wakeup. 83*9356374aSAndroid Build Coastguard Worker struct timespec MakeRelativeTimespec() const; 84*9356374aSAndroid Build Coastguard Worker 85*9356374aSAndroid Build Coastguard Worker #ifndef _WIN32 86*9356374aSAndroid Build Coastguard Worker // Convert to `struct timespec` for interfaces that expect an absolute timeout 87*9356374aSAndroid Build Coastguard Worker // on a specific clock `c`. This is similar to `MakeAbsTimespec()`, but 88*9356374aSAndroid Build Coastguard Worker // callers usually want to use this method with `CLOCK_MONOTONIC` when 89*9356374aSAndroid Build Coastguard Worker // relative timeouts are requested, and when the appropriate interface expects 90*9356374aSAndroid Build Coastguard Worker // an absolute timeout relative to a specific clock (for example, 91*9356374aSAndroid Build Coastguard Worker // pthread_cond_clockwait() or sem_clockwait()). If !has_timeout(), attempts 92*9356374aSAndroid Build Coastguard Worker // to convert to a reasonable absolute timeout, but callers should to test 93*9356374aSAndroid Build Coastguard Worker // has_timeout() prefer to use a more appropriate interface. 94*9356374aSAndroid Build Coastguard Worker struct timespec MakeClockAbsoluteTimespec(clockid_t c) const; 95*9356374aSAndroid Build Coastguard Worker #endif 96*9356374aSAndroid Build Coastguard Worker 97*9356374aSAndroid Build Coastguard Worker // Convert to unix epoch nanos for interfaces that expect an absolute timeout 98*9356374aSAndroid Build Coastguard Worker // in nanoseconds. If !has_timeout() or is_relative_timeout(), attempts to 99*9356374aSAndroid Build Coastguard Worker // convert to a reasonable absolute timeout, but callers should to test 100*9356374aSAndroid Build Coastguard Worker // has_timeout() and is_relative_timeout() and prefer to use a more 101*9356374aSAndroid Build Coastguard Worker // appropriate interface. 102*9356374aSAndroid Build Coastguard Worker int64_t MakeAbsNanos() const; 103*9356374aSAndroid Build Coastguard Worker 104*9356374aSAndroid Build Coastguard Worker // Converts to milliseconds from now, or INFINITE when 105*9356374aSAndroid Build Coastguard Worker // !has_timeout(). For use by SleepConditionVariableSRW on 106*9356374aSAndroid Build Coastguard Worker // Windows. Callers should recognize that the return value is a 107*9356374aSAndroid Build Coastguard Worker // relative duration (it should be recomputed by calling this method 108*9356374aSAndroid Build Coastguard Worker // in the case of a spurious wakeup). 109*9356374aSAndroid Build Coastguard Worker // This header file may be included transitively by public header files, 110*9356374aSAndroid Build Coastguard Worker // so we define our own DWORD and INFINITE instead of getting them from 111*9356374aSAndroid Build Coastguard Worker // <intsafe.h> and <WinBase.h>. 112*9356374aSAndroid Build Coastguard Worker typedef unsigned long DWord; // NOLINT 113*9356374aSAndroid Build Coastguard Worker DWord InMillisecondsFromNow() const; 114*9356374aSAndroid Build Coastguard Worker 115*9356374aSAndroid Build Coastguard Worker // Convert to std::chrono::time_point for interfaces that expect an absolute 116*9356374aSAndroid Build Coastguard Worker // timeout, like std::condition_variable::wait_until(). If !has_timeout() or 117*9356374aSAndroid Build Coastguard Worker // is_relative_timeout(), attempts to convert to a reasonable absolute 118*9356374aSAndroid Build Coastguard Worker // timeout, but callers should test has_timeout() and is_relative_timeout() 119*9356374aSAndroid Build Coastguard Worker // and prefer to use a more appropriate interface. 120*9356374aSAndroid Build Coastguard Worker std::chrono::time_point<std::chrono::system_clock> ToChronoTimePoint() const; 121*9356374aSAndroid Build Coastguard Worker 122*9356374aSAndroid Build Coastguard Worker // Convert to std::chrono::time_point for interfaces that expect a relative 123*9356374aSAndroid Build Coastguard Worker // timeout, like std::condition_variable::wait_for(). If !has_timeout() or 124*9356374aSAndroid Build Coastguard Worker // is_absolute_timeout(), attempts to convert to a reasonable relative 125*9356374aSAndroid Build Coastguard Worker // timeout, but callers should test has_timeout() and is_absolute_timeout() 126*9356374aSAndroid Build Coastguard Worker // and prefer to use a more appropriate interface. Since the return value is a 127*9356374aSAndroid Build Coastguard Worker // relative duration, it should be recomputed by calling this method in the 128*9356374aSAndroid Build Coastguard Worker // case of a spurious wakeup. 129*9356374aSAndroid Build Coastguard Worker std::chrono::nanoseconds ToChronoDuration() const; 130*9356374aSAndroid Build Coastguard Worker 131*9356374aSAndroid Build Coastguard Worker // Returns true if steady (aka monotonic) clocks are supported by the system. 132*9356374aSAndroid Build Coastguard Worker // This method exists because go/btm requires synchronized clocks, and 133*9356374aSAndroid Build Coastguard Worker // thus requires we use the system (aka walltime) clock. SupportsSteadyClock()134*9356374aSAndroid Build Coastguard Worker static constexpr bool SupportsSteadyClock() { return true; } 135*9356374aSAndroid Build Coastguard Worker 136*9356374aSAndroid Build Coastguard Worker private: 137*9356374aSAndroid Build Coastguard Worker // Returns the current time, expressed as a count of nanoseconds since the 138*9356374aSAndroid Build Coastguard Worker // epoch used by an arbitrary clock. The implementation tries to use a steady 139*9356374aSAndroid Build Coastguard Worker // (monotonic) clock if one is available. 140*9356374aSAndroid Build Coastguard Worker static int64_t SteadyClockNow(); 141*9356374aSAndroid Build Coastguard Worker 142*9356374aSAndroid Build Coastguard Worker // Internal representation. 143*9356374aSAndroid Build Coastguard Worker // - If the value is kNoTimeout, then the timeout is infinite, and 144*9356374aSAndroid Build Coastguard Worker // has_timeout() will return true. 145*9356374aSAndroid Build Coastguard Worker // - If the low bit is 0, then the high 63 bits is the number of nanoseconds 146*9356374aSAndroid Build Coastguard Worker // after the unix epoch. 147*9356374aSAndroid Build Coastguard Worker // - If the low bit is 1, then the high 63 bits is the number of nanoseconds 148*9356374aSAndroid Build Coastguard Worker // after the epoch used by SteadyClockNow(). 149*9356374aSAndroid Build Coastguard Worker // 150*9356374aSAndroid Build Coastguard Worker // In all cases the time is stored as an absolute time, the only difference is 151*9356374aSAndroid Build Coastguard Worker // the clock epoch. The use of absolute times is important since in the case 152*9356374aSAndroid Build Coastguard Worker // of a relative timeout with a spurious wakeup, the program would have to 153*9356374aSAndroid Build Coastguard Worker // restart the wait, and thus needs a way of recomputing the remaining time. 154*9356374aSAndroid Build Coastguard Worker uint64_t rep_; 155*9356374aSAndroid Build Coastguard Worker 156*9356374aSAndroid Build Coastguard Worker // Returns the number of nanoseconds stored in the internal representation. 157*9356374aSAndroid Build Coastguard Worker // When combined with the clock epoch indicated by the low bit (which is 158*9356374aSAndroid Build Coastguard Worker // accessed through is_absolute_timeout() and is_relative_timeout()), the 159*9356374aSAndroid Build Coastguard Worker // return value is used to compute when the timeout should occur. RawAbsNanos()160*9356374aSAndroid Build Coastguard Worker int64_t RawAbsNanos() const { return static_cast<int64_t>(rep_ >> 1); } 161*9356374aSAndroid Build Coastguard Worker 162*9356374aSAndroid Build Coastguard Worker // Converts to nanoseconds from now. Since the return value is a relative 163*9356374aSAndroid Build Coastguard Worker // duration, it should be recomputed by calling this method in the case of a 164*9356374aSAndroid Build Coastguard Worker // spurious wakeup. 165*9356374aSAndroid Build Coastguard Worker int64_t InNanosecondsFromNow() const; 166*9356374aSAndroid Build Coastguard Worker 167*9356374aSAndroid Build Coastguard Worker // A value that represents no timeout (or an infinite timeout). 168*9356374aSAndroid Build Coastguard Worker static constexpr uint64_t kNoTimeout = (std::numeric_limits<uint64_t>::max)(); 169*9356374aSAndroid Build Coastguard Worker 170*9356374aSAndroid Build Coastguard Worker // The maximum value that can be stored in the high 63 bits. 171*9356374aSAndroid Build Coastguard Worker static constexpr int64_t kMaxNanos = (std::numeric_limits<int64_t>::max)(); 172*9356374aSAndroid Build Coastguard Worker }; 173*9356374aSAndroid Build Coastguard Worker 174*9356374aSAndroid Build Coastguard Worker } // namespace synchronization_internal 175*9356374aSAndroid Build Coastguard Worker ABSL_NAMESPACE_END 176*9356374aSAndroid Build Coastguard Worker } // namespace absl 177*9356374aSAndroid Build Coastguard Worker 178*9356374aSAndroid Build Coastguard Worker #endif // ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ 179