[libc-commits] [libc] b342d18 - [libc] add timeout and clock conversion utilities (#91905)
via libc-commits
libc-commits at lists.llvm.org
Mon May 13 16:00:24 PDT 2024
Author: Schrodinger ZHU Yifan
Date: 2024-05-13T19:00:19-04:00
New Revision: b342d18a8f0240342ea5c461145e78c6e3af92cc
URL: https://github.com/llvm/llvm-project/commit/b342d18a8f0240342ea5c461145e78c6e3af92cc
DIFF: https://github.com/llvm/llvm-project/commit/b342d18a8f0240342ea5c461145e78c6e3af92cc.diff
LOG: [libc] add timeout and clock conversion utilities (#91905)
This PR:
- Make `clock_gettime` a header-only library
- Add `clock_conversion` header library to allow conversion between
clocks relative to the time of call
- Add `timeout` header library to manage the absolute timeout used in
POSIX's timed locking/waiting APIs
Added:
libc/src/__support/time/linux/abs_timeout.h
libc/src/__support/time/linux/clock_conversion.h
libc/src/__support/time/linux/monotonicity.h
libc/test/src/__support/time/CMakeLists.txt
libc/test/src/__support/time/linux/CMakeLists.txt
libc/test/src/__support/time/linux/timeout_test.cpp
Modified:
libc/src/__support/threads/linux/CMakeLists.txt
libc/src/__support/threads/linux/futex_utils.h
libc/src/__support/time/linux/CMakeLists.txt
libc/src/__support/time/linux/clock_gettime.h
libc/test/src/__support/CMakeLists.txt
Removed:
libc/src/__support/time/linux/clock_gettime.cpp
################################################################################
diff --git a/libc/src/__support/threads/linux/CMakeLists.txt b/libc/src/__support/threads/linux/CMakeLists.txt
index 9bee30206f1b9..d3353f6b3ff8c 100644
--- a/libc/src/__support/threads/linux/CMakeLists.txt
+++ b/libc/src/__support/threads/linux/CMakeLists.txt
@@ -19,7 +19,7 @@ add_header_library(
libc.src.__support.CPP.atomic
libc.src.__support.CPP.limits
libc.src.__support.CPP.optional
- libc.hdr.types.struct_timespec
+ libc.src.__support.time.linux.abs_timeout
)
add_header_library(
diff --git a/libc/src/__support/threads/linux/futex_utils.h b/libc/src/__support/threads/linux/futex_utils.h
index 1fbce4f7bf438..e40ade8e709b1 100644
--- a/libc/src/__support/threads/linux/futex_utils.h
+++ b/libc/src/__support/threads/linux/futex_utils.h
@@ -9,23 +9,20 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_FUTEX_UTILS_H
#define LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_FUTEX_UTILS_H
-#include "hdr/types/struct_timespec.h"
#include "src/__support/CPP/atomic.h"
#include "src/__support/CPP/limits.h"
#include "src/__support/CPP/optional.h"
#include "src/__support/OSUtil/syscall.h"
#include "src/__support/macros/attributes.h"
#include "src/__support/threads/linux/futex_word.h"
+#include "src/__support/time/linux/abs_timeout.h"
#include <linux/errno.h>
#include <linux/futex.h>
namespace LIBC_NAMESPACE {
class Futex : public cpp::Atomic<FutexWordType> {
public:
- struct Timeout {
- timespec abs_time;
- bool is_realtime;
- };
+ using Timeout = internal::AbsTimeout;
LIBC_INLINE constexpr Futex(FutexWordType value)
: cpp::Atomic<FutexWordType>(value) {}
LIBC_INLINE Futex &operator=(FutexWordType value) {
@@ -37,7 +34,7 @@ class Futex : public cpp::Atomic<FutexWordType> {
bool is_shared = false) {
// use bitset variants to enforce abs_time
uint32_t op = is_shared ? FUTEX_WAIT_BITSET : FUTEX_WAIT_BITSET_PRIVATE;
- if (timeout && timeout->is_realtime) {
+ if (timeout && timeout->is_realtime()) {
op |= FUTEX_CLOCK_REALTIME;
}
for (;;) {
@@ -49,7 +46,7 @@ class Futex : public cpp::Atomic<FutexWordType> {
/* futex address */ this,
/* futex operation */ op,
/* expected value */ expected,
- /* timeout */ timeout ? &timeout->abs_time : nullptr,
+ /* timeout */ timeout ? &timeout->get_timespec() : nullptr,
/* ignored */ nullptr,
/* bitset */ FUTEX_BITSET_MATCH_ANY);
diff --git a/libc/src/__support/time/linux/CMakeLists.txt b/libc/src/__support/time/linux/CMakeLists.txt
index f04d550555e19..1b41c7cb0a98a 100644
--- a/libc/src/__support/time/linux/CMakeLists.txt
+++ b/libc/src/__support/time/linux/CMakeLists.txt
@@ -1,9 +1,7 @@
-add_object_library(
+add_header_library(
clock_gettime
HDRS
clock_gettime.h
- SRCS
- clock_gettime.cpp
DEPENDS
libc.include.sys_syscall
libc.hdr.types.struct_timespec
@@ -12,3 +10,32 @@ add_object_library(
libc.src.__support.error_or
libc.src.__support.OSUtil.osutil
)
+
+add_header_library(
+ clock_conversion
+ HDRS
+ clock_conversion.h
+ DEPENDS
+ .clock_gettime
+ libc.src.__support.time.units
+)
+
+add_header_library(
+ abs_timeout
+ HDRS
+ abs_timeout.h
+ DEPENDS
+ libc.hdr.types.struct_timespec
+ libc.src.__support.time.units
+ libc.src.__support.CPP.expected
+)
+
+add_header_library(
+ monotonicity
+ HDRS
+ monotonicity.h
+ DEPENDS
+ .clock_conversion
+ .abs_timeout
+ libc.hdr.time_macros
+)
diff --git a/libc/src/__support/time/linux/abs_timeout.h b/libc/src/__support/time/linux/abs_timeout.h
new file mode 100644
index 0000000000000..6e5e59b32b7ad
--- /dev/null
+++ b/libc/src/__support/time/linux/abs_timeout.h
@@ -0,0 +1,49 @@
+//===--- Linux absolute timeout ---------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H
+#define LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H
+
+#include "hdr/time_macros.h"
+#include "hdr/types/struct_timespec.h"
+#include "src/__support/CPP/expected.h"
+#include "src/__support/time/units.h"
+
+namespace LIBC_NAMESPACE {
+namespace internal {
+// We use AbsTimeout to remind ourselves that the timeout is an absolute time.
+// This is a simple wrapper around the timespec struct that also keeps track of
+// whether the time is in realtime or monotonic time.
+class AbsTimeout {
+ timespec timeout;
+ bool realtime_flag;
+ LIBC_INLINE constexpr explicit AbsTimeout(timespec ts, bool realtime)
+ : timeout(ts), realtime_flag(realtime) {}
+
+public:
+ enum class Error { Invalid, BeforeEpoch };
+ LIBC_INLINE const timespec &get_timespec() const { return timeout; }
+ LIBC_INLINE bool is_realtime() const { return realtime_flag; }
+ LIBC_INLINE static constexpr cpp::expected<AbsTimeout, Error>
+ from_timespec(timespec ts, bool realtime) {
+ using namespace time_units;
+ if (ts.tv_nsec < 0 || ts.tv_nsec >= 1_s_ns)
+ return cpp::unexpected<Error>(Error::Invalid);
+
+ // POSIX allows tv_sec to be negative. We interpret this as an expired
+ // timeout.
+ if (ts.tv_sec < 0)
+ return cpp::unexpected<Error>(Error::BeforeEpoch);
+
+ return AbsTimeout{ts, realtime};
+ }
+};
+} // namespace internal
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H
diff --git a/libc/src/__support/time/linux/clock_conversion.h b/libc/src/__support/time/linux/clock_conversion.h
new file mode 100644
index 0000000000000..4a7c8ff284849
--- /dev/null
+++ b/libc/src/__support/time/linux/clock_conversion.h
@@ -0,0 +1,42 @@
+//===--- clock conversion linux implementation ------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_CONVERSION_H
+#define LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_CONVERSION_H
+
+#include "src/__support/time/linux/clock_gettime.h"
+#include "src/__support/time/units.h"
+
+namespace LIBC_NAMESPACE {
+namespace internal {
+
+LIBC_INLINE timespec convert_clock(timespec input, clockid_t from,
+ clockid_t to) {
+ using namespace time_units;
+ timespec from_time;
+ timespec to_time;
+ timespec output;
+ internal::clock_gettime(from, &from_time);
+ internal::clock_gettime(to, &to_time);
+ output.tv_sec = input.tv_sec - from_time.tv_sec + to_time.tv_sec;
+ output.tv_nsec = input.tv_nsec - from_time.tv_nsec + to_time.tv_nsec;
+
+ if (output.tv_nsec > 1_s_ns) {
+ output.tv_sec++;
+ output.tv_nsec -= 1_s_ns;
+ } else if (output.tv_nsec < 0) {
+ output.tv_sec--;
+ output.tv_nsec += 1_s_ns;
+ }
+ return output;
+}
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_CONVERSION_H
diff --git a/libc/src/__support/time/linux/clock_gettime.cpp b/libc/src/__support/time/linux/clock_gettime.cpp
deleted file mode 100644
index 7f266b282a391..0000000000000
--- a/libc/src/__support/time/linux/clock_gettime.cpp
+++ /dev/null
@@ -1,35 +0,0 @@
-//===--- clock_gettime linux implementation ---------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "src/__support/time/linux/clock_gettime.h"
-#include "src/__support/OSUtil/syscall.h"
-#include <sys/syscall.h>
-namespace LIBC_NAMESPACE {
-namespace internal {
-ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts) {
-#if SYS_clock_gettime
- int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
- static_cast<long>(clockid),
- reinterpret_cast<long>(ts));
-#elif defined(SYS_clock_gettime64)
- static_assert(
- sizeof(time_t) == sizeof(int64_t),
- "SYS_clock_gettime64 requires struct timespec with 64-bit members.");
- int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime64,
- static_cast<long>(clockid),
- reinterpret_cast<long>(ts));
-#else
-#error "SYS_clock_gettime and SYS_clock_gettime64 syscalls not available."
-#endif
- if (ret < 0)
- return Error(-ret);
- return ret;
-}
-
-} // namespace internal
-} // namespace LIBC_NAMESPACE
diff --git a/libc/src/__support/time/linux/clock_gettime.h b/libc/src/__support/time/linux/clock_gettime.h
index b1572726f6301..bbdde98551abe 100644
--- a/libc/src/__support/time/linux/clock_gettime.h
+++ b/libc/src/__support/time/linux/clock_gettime.h
@@ -8,16 +8,37 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_GETTIME_H
#define LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_GETTIME_H
+
#include "hdr/types/clockid_t.h"
#include "hdr/types/struct_timespec.h"
+#include "src/__support/OSUtil/syscall.h"
#include "src/__support/common.h"
-
#include "src/__support/error_or.h"
+#include <sys/syscall.h>
namespace LIBC_NAMESPACE {
namespace internal {
-ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts);
+LIBC_INLINE ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts) {
+#if SYS_clock_gettime
+ int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
+ static_cast<long>(clockid),
+ reinterpret_cast<long>(ts));
+#elif defined(SYS_clock_gettime64)
+ static_assert(
+ sizeof(time_t) == sizeof(int64_t),
+ "SYS_clock_gettime64 requires struct timespec with 64-bit members.");
+ int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime64,
+ static_cast<long>(clockid),
+ reinterpret_cast<long>(ts));
+#else
+#error "SYS_clock_gettime and SYS_clock_gettime64 syscalls not available."
+#endif
+ if (ret < 0)
+ return Error(-ret);
+ return ret;
}
+
+} // namespace internal
} // namespace LIBC_NAMESPACE
#endif // LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_CLOCK_GETTIME_H
diff --git a/libc/src/__support/time/linux/monotonicity.h b/libc/src/__support/time/linux/monotonicity.h
new file mode 100644
index 0000000000000..e413275430dd1
--- /dev/null
+++ b/libc/src/__support/time/linux/monotonicity.h
@@ -0,0 +1,43 @@
+//===--- timeout linux implementation ---------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_MONOTONICITY_H
+#define LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_MONOTONICITY_H
+
+#include "hdr/time_macros.h"
+#include "src/__support/libc_assert.h"
+#include "src/__support/time/linux/abs_timeout.h"
+#include "src/__support/time/linux/clock_conversion.h"
+namespace LIBC_NAMESPACE {
+namespace internal {
+// This function is separated from abs_timeout.
+// This function pulls in the dependency to clock_conversion.h,
+// which may transitively depend on vDSO hence futex. However, this structure
+// would be passed to futex, so we need to avoid cyclic dependencies.
+// This function is going to be used in timed locks. Pthread generally uses
+// realtime clocks for timeouts. However, due to non-monotoncity, realtime
+// clocks reportedly lead to undesired behaviors. Therefore, we also provide a
+// method to convert the timespec to a monotonic clock relative to the time of
+// function call.
+LIBC_INLINE void ensure_monotonicity(AbsTimeout &timeout) {
+ if (timeout.is_realtime()) {
+ auto res = AbsTimeout::from_timespec(
+ convert_clock(timeout.get_timespec(), CLOCK_REALTIME, CLOCK_MONOTONIC),
+ false);
+
+ LIBC_ASSERT(res.has_value());
+ if (!res.has_value())
+ __builtin_unreachable();
+
+ timeout = *res;
+ }
+}
+} // namespace internal
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_MONOTONICITY_H
diff --git a/libc/test/src/__support/CMakeLists.txt b/libc/test/src/__support/CMakeLists.txt
index 5d1230f5f3a70..8bdc56ee59ccc 100644
--- a/libc/test/src/__support/CMakeLists.txt
+++ b/libc/test/src/__support/CMakeLists.txt
@@ -206,3 +206,4 @@ add_subdirectory(OSUtil)
add_subdirectory(FPUtil)
add_subdirectory(fixed_point)
add_subdirectory(HashTable)
+add_subdirectory(time)
diff --git a/libc/test/src/__support/time/CMakeLists.txt b/libc/test/src/__support/time/CMakeLists.txt
new file mode 100644
index 0000000000000..37062e131acf5
--- /dev/null
+++ b/libc/test/src/__support/time/CMakeLists.txt
@@ -0,0 +1,5 @@
+add_custom_target(libc-support-time-tests)
+
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+ add_subdirectory(${LIBC_TARGET_OS})
+endif()
diff --git a/libc/test/src/__support/time/linux/CMakeLists.txt b/libc/test/src/__support/time/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..3174986283dd8
--- /dev/null
+++ b/libc/test/src/__support/time/linux/CMakeLists.txt
@@ -0,0 +1,9 @@
+add_libc_test(
+ timeout_test
+ SUITE libc-support-time-tests
+ SRCS timeout_test.cpp
+ DEPENDS
+ libc.src.__support.time.linux.abs_timeout
+ libc.src.__support.time.linux.monotonicity
+ libc.src.__support.CPP.expected
+)
diff --git a/libc/test/src/__support/time/linux/timeout_test.cpp b/libc/test/src/__support/time/linux/timeout_test.cpp
new file mode 100644
index 0000000000000..886d4389709e8
--- /dev/null
+++ b/libc/test/src/__support/time/linux/timeout_test.cpp
@@ -0,0 +1,60 @@
+//===-- unit tests for linux's timeout utilities --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/expected.h"
+#include "src/__support/time/linux/abs_timeout.h"
+#include "src/__support/time/linux/monotonicity.h"
+#include "test/UnitTest/Test.h"
+
+template <class T, class E>
+using expected = LIBC_NAMESPACE::cpp::expected<T, E>;
+using AbsTimeout = LIBC_NAMESPACE::internal::AbsTimeout;
+
+TEST(LlvmLibcSupportLinuxTimeoutTest, NegativeSecond) {
+ timespec ts = {-1, 0};
+ expected<AbsTimeout, AbsTimeout::Error> result =
+ AbsTimeout::from_timespec(ts, false);
+ ASSERT_FALSE(result.has_value());
+ ASSERT_EQ(result.error(), AbsTimeout::Error::BeforeEpoch);
+}
+TEST(LlvmLibcSupportLinuxTimeoutTest, OverflowNano) {
+ using namespace LIBC_NAMESPACE::time_units;
+ timespec ts = {0, 2_s_ns};
+ expected<AbsTimeout, AbsTimeout::Error> result =
+ AbsTimeout::from_timespec(ts, false);
+ ASSERT_FALSE(result.has_value());
+ ASSERT_EQ(result.error(), AbsTimeout::Error::Invalid);
+}
+TEST(LlvmLibcSupportLinuxTimeoutTest, UnderflowNano) {
+ timespec ts = {0, -1};
+ expected<AbsTimeout, AbsTimeout::Error> result =
+ AbsTimeout::from_timespec(ts, false);
+ ASSERT_FALSE(result.has_value());
+ ASSERT_EQ(result.error(), AbsTimeout::Error::Invalid);
+}
+TEST(LlvmLibcSupportLinuxTimeoutTest, NoChangeIfClockIsMonotonic) {
+ timespec ts = {10000, 0};
+ expected<AbsTimeout, AbsTimeout::Error> result =
+ AbsTimeout::from_timespec(ts, false);
+ ASSERT_TRUE(result.has_value());
+ ensure_monotonicity(*result);
+ ASSERT_FALSE(result->is_realtime());
+ ASSERT_EQ(result->get_timespec().tv_sec, static_cast<time_t>(10000));
+ ASSERT_EQ(result->get_timespec().tv_nsec, static_cast<time_t>(0));
+}
+TEST(LlvmLibcSupportLinuxTimeoutTest, ValidAfterConversion) {
+ timespec ts;
+ LIBC_NAMESPACE::internal::clock_gettime(CLOCK_REALTIME, &ts);
+ expected<AbsTimeout, AbsTimeout::Error> result =
+ AbsTimeout::from_timespec(ts, true);
+ ASSERT_TRUE(result.has_value());
+ ensure_monotonicity(*result);
+ ASSERT_FALSE(result->is_realtime());
+ ASSERT_TRUE(
+ AbsTimeout::from_timespec(result->get_timespec(), false).has_value());
+}
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