From 0372af19f2f4f588351ca8f71b3f528cbe467a4d Mon Sep 17 00:00:00 2001 From: Derek Mauro Date: Thu, 16 Feb 2023 11:52:26 -0800 Subject: Add KernelTimeout methods that convert the timeout to the std::chrono methods used by std::condition_variable. A followup change will add an implemention of synchronization_internal::Waiter that can use std:mutex/std::condition_variable to implement the per-thread semaphore that absl::Mutex waits on. This implementation may at some point become the default on platforms such as Windows where there doesn't seem to be an easy way of supporting real absolute timeouts. In this case we can defer to their standard library to implement correct support. PiperOrigin-RevId: 510204786 Change-Id: Icf4d695013fd060abbd53dae23e71ea36f731565 --- absl/synchronization/internal/kernel_timeout.cc | 41 ++++++++++++++++++++++ absl/synchronization/internal/kernel_timeout.h | 15 ++++++++ .../internal/kernel_timeout_test.cc | 38 ++++++++++++++++++++ 3 files changed, 94 insertions(+) (limited to 'absl/synchronization') diff --git a/absl/synchronization/internal/kernel_timeout.cc b/absl/synchronization/internal/kernel_timeout.cc index 8d9e7d74..548a8fc6 100644 --- a/absl/synchronization/internal/kernel_timeout.cc +++ b/absl/synchronization/internal/kernel_timeout.cc @@ -15,6 +15,7 @@ #include "absl/synchronization/internal/kernel_timeout.h" #include +#include // NOLINT(build/c++11) #include #include #include @@ -163,6 +164,46 @@ KernelTimeout::DWord KernelTimeout::InMillisecondsFromNow() const { return DWord{0}; } +std::chrono::time_point +KernelTimeout::ToChronoTimePoint() const { + if (!has_timeout()) { + return std::chrono::time_point::max(); + } + + // The cast to std::microseconds is because (on some platforms) the + // std::ratio used by std::chrono::steady_clock doesn't convert to + // std::nanoseconds, so it doesn't compile. + auto micros = std::chrono::duration_cast( + std::chrono::nanoseconds(RawNanos())); + if (is_relative_timeout()) { + auto now = std::chrono::system_clock::now(); + if (micros > + std::chrono::time_point::max() - now) { + // Overflow. + return std::chrono::time_point::max(); + } + return now + micros; + } + return std::chrono::system_clock::from_time_t(0) + micros; +} + +std::chrono::nanoseconds KernelTimeout::ToChronoDuration() const { + if (!has_timeout()) { + return std::chrono::nanoseconds::max(); + } + if (is_absolute_timeout()) { + auto d = std::chrono::duration_cast( + std::chrono::nanoseconds(RawNanos()) - + (std::chrono::system_clock::now() - + std::chrono::system_clock::from_time_t(0))); + if (d < std::chrono::nanoseconds(0)) { + d = std::chrono::nanoseconds(0); + } + return d; + } + return std::chrono::nanoseconds(RawNanos()); +} + } // namespace synchronization_internal ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/synchronization/internal/kernel_timeout.h b/absl/synchronization/internal/kernel_timeout.h index 1f4d82cd..f7c40337 100644 --- a/absl/synchronization/internal/kernel_timeout.h +++ b/absl/synchronization/internal/kernel_timeout.h @@ -16,6 +16,7 @@ #define ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ #include +#include // NOLINT(build/c++11) #include #include #include @@ -95,6 +96,20 @@ class KernelTimeout { typedef unsigned long DWord; // NOLINT DWord InMillisecondsFromNow() const; + // Convert to std::chrono::time_point for interfaces that expect an absolute + // timeout, like std::condition_variable::wait_until(). If !has_timeout() or + // is_relative_timeout(), attempts to convert to a reasonable absolute + // timeout, but callers should test has_timeout() and is_relative_timeout() + // and prefer to use a more appropriate interface. + std::chrono::time_point ToChronoTimePoint() const; + + // Convert to std::chrono::time_point for interfaces that expect a relative + // timeout, like std::condition_variable::wait_for(). If !has_timeout() or + // is_absolute_timeout(), attempts to convert to a reasonable relative + // timeout, but callers should test has_timeout() and is_absolute_timeout() + // and prefer to use a more appropriate interface. + std::chrono::nanoseconds ToChronoDuration() const; + private: // Internal representation. // - If the value is kNoTimeout, then the timeout is infinite, and diff --git a/absl/synchronization/internal/kernel_timeout_test.cc b/absl/synchronization/internal/kernel_timeout_test.cc index a89ae220..431ffcf4 100644 --- a/absl/synchronization/internal/kernel_timeout_test.cc +++ b/absl/synchronization/internal/kernel_timeout_test.cc @@ -14,6 +14,7 @@ #include "absl/synchronization/internal/kernel_timeout.h" +#include // NOLINT(build/c++11) #include #include "gtest/gtest.h" @@ -72,6 +73,11 @@ TEST(KernelTimeout, FiniteTimes) { EXPECT_LE(absl::AbsDuration(absl::Milliseconds(t.InMillisecondsFromNow()) - std::max(duration, absl::ZeroDuration())), absl::Milliseconds(5)); + EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoTimePoint()) - when), + absl::Microseconds(1)); + EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoDuration()) - + std::max(duration, absl::ZeroDuration())), + kTimingBound); } } @@ -90,6 +96,9 @@ TEST(KernelTimeout, InfiniteFuture) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, DefaultConstructor) { @@ -108,6 +117,9 @@ TEST(KernelTimeout, DefaultConstructor) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, TimeMaxNanos) { @@ -126,6 +138,9 @@ TEST(KernelTimeout, TimeMaxNanos) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, Never) { @@ -144,6 +159,9 @@ TEST(KernelTimeout, Never) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, InfinitePast) { @@ -157,6 +175,9 @@ TEST(KernelTimeout, InfinitePast) { absl::ZeroDuration()); EXPECT_LE(absl::FromUnixNanos(t.MakeAbsNanos()), absl::FromUnixNanos(1)); EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0}); + EXPECT_LT(t.ToChronoTimePoint(), std::chrono::system_clock::from_time_t(0) + + std::chrono::seconds(1)); + EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0)); } TEST(KernelTimeout, FiniteDurations) { @@ -186,6 +207,10 @@ TEST(KernelTimeout, FiniteDurations) { absl::Milliseconds(5)); EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration, absl::Milliseconds(5)); + EXPECT_LE(absl::AbsDuration(absl::Now() + duration - + absl::FromChrono(t.ToChronoTimePoint())), + kTimingBound); + EXPECT_EQ(absl::FromChrono(t.ToChronoDuration()), duration); } } @@ -218,6 +243,10 @@ TEST(KernelTimeout, NegativeDurations) { absl::AbsDuration(absl::Now() - absl::FromUnixNanos(t.MakeAbsNanos())), absl::Milliseconds(5)); EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0}); + EXPECT_LE(absl::AbsDuration(absl::Now() - + absl::FromChrono(t.ToChronoTimePoint())), + absl::Milliseconds(5)); + EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0)); } } @@ -236,6 +265,9 @@ TEST(KernelTimeout, InfiniteDuration) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, DurationMaxNanos) { @@ -254,6 +286,9 @@ TEST(KernelTimeout, DurationMaxNanos) { absl::Now() + absl::Hours(100000)); EXPECT_EQ(t.InMillisecondsFromNow(), std::numeric_limits::max()); + EXPECT_EQ(t.ToChronoTimePoint(), + std::chrono::time_point::max()); + EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max()); } TEST(KernelTimeout, OverflowNanos) { @@ -273,6 +308,9 @@ TEST(KernelTimeout, OverflowNanos) { absl::Now() + absl::Hours(100000)); EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration, absl::Milliseconds(5)); + EXPECT_GT(t.ToChronoTimePoint(), + std::chrono::system_clock::now() + std::chrono::hours(100000)); + EXPECT_GT(t.ToChronoDuration(), std::chrono::hours(100000)); } } // namespace -- cgit v1.2.3