diff options
| -rw-r--r-- | libstdc++-v3/include/std/future | 14 | ||||
| -rw-r--r-- | libstdc++-v3/src/c++11/futex.cc | 9 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/30_threads/future/members/poll.cc | 103 |
3 files changed, 123 insertions, 3 deletions
diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future index 5d94801..f7617ca 100644 --- a/libstdc++-v3/include/std/future +++ b/libstdc++-v3/include/std/future @@ -345,10 +345,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // to synchronize with the thread that made it ready. if (_M_status._M_load(memory_order_acquire) == _Status::__ready) return future_status::ready; + if (_M_is_deferred_future()) return future_status::deferred; - if (_M_status._M_load_when_equal_for(_Status::__ready, - memory_order_acquire, __rel)) + + // Don't wait unless the relative time is greater than zero. + if (__rel > __rel.zero() + && _M_status._M_load_when_equal_for(_Status::__ready, + memory_order_acquire, + __rel)) { // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2100. timed waiting functions must also join @@ -377,10 +382,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // to synchronize with the thread that made it ready. if (_M_status._M_load(memory_order_acquire) == _Status::__ready) return future_status::ready; + if (_M_is_deferred_future()) return future_status::deferred; + if (_M_status._M_load_when_equal_until(_Status::__ready, - memory_order_acquire, __abs)) + memory_order_acquire, + __abs)) { // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2100. timed waiting functions must also join diff --git a/libstdc++-v3/src/c++11/futex.cc b/libstdc++-v3/src/c++11/futex.cc index 0331bd6..57f7dfe 100644 --- a/libstdc++-v3/src/c++11/futex.cc +++ b/libstdc++-v3/src/c++11/futex.cc @@ -78,6 +78,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct timespec rt; rt.tv_sec = __s.count(); rt.tv_nsec = __ns.count(); + + // futex sets errno=EINVAL for absolute timeouts before the epoch. + if (__builtin_expect(rt.tv_sec < 0, false)) + return false; + if (syscall (SYS_futex, __addr, futex_wait_bitset_op | futex_clock_realtime_flag, __val, &rt, nullptr, futex_bitset_match_any) == -1) @@ -151,6 +156,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION rt.tv_sec = __s.count(); rt.tv_nsec = __ns.count(); + // futex sets errno=EINVAL for absolute timeouts before the epoch. + if (__builtin_expect(rt.tv_sec < 0, false)) + return false; + if (syscall (SYS_futex, __addr, futex_wait_bitset_op | futex_clock_monotonic_flag, __val, &rt, nullptr, futex_bitset_match_any) == -1) diff --git a/libstdc++-v3/testsuite/30_threads/future/members/poll.cc b/libstdc++-v3/testsuite/30_threads/future/members/poll.cc new file mode 100644 index 0000000..5458057 --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/future/members/poll.cc @@ -0,0 +1,103 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +// { dg-options "-O3" } +// { dg-do run { target c++11 } } + +#include <future> +#include <chrono> +#include <iostream> +#include <testsuite_hooks.h> + +const int iterations = 200; + +using namespace std; + +template<typename Duration> +double +print(const char* desc, Duration dur) +{ + auto ns = chrono::duration_cast<chrono::nanoseconds>(dur).count(); + double d = double(ns) / iterations; + cout << desc << ": " << ns << "ns for " << iterations + << " calls, avg " << d << "ns per call\n"; + return d; +} + +int main() +{ + promise<int> p; + future<int> f = p.get_future(); + + auto start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_for(chrono::seconds(0)); + auto stop = chrono::high_resolution_clock::now(); + double wait_for_0 = print("wait_for(0s)", stop - start); + + start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_until(chrono::system_clock::time_point()); + stop = chrono::high_resolution_clock::now(); + double wait_until_sys_epoch __attribute__((unused)) + = print("wait_until(system_clock epoch)", stop - start); + + start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_until(chrono::steady_clock::time_point()); + stop = chrono::high_resolution_clock::now(); + double wait_until_steady_epoch __attribute__((unused)) + = print("wait_until(steady_clock epoch", stop - start); + + start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_until(chrono::system_clock::time_point::min()); + stop = chrono::high_resolution_clock::now(); + double wait_until_sys_min __attribute__((unused)) + = print("wait_until(system_clock minimum)", stop - start); + + start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_until(chrono::steady_clock::time_point::min()); + stop = chrono::high_resolution_clock::now(); + double wait_until_steady_min __attribute__((unused)) + = print("wait_until(steady_clock minimum)", stop - start); + + p.set_value(1); + + start = chrono::high_resolution_clock::now(); + for(int i = 0; i < iterations; i++) + f.wait_for(chrono::seconds(0)); + stop = chrono::high_resolution_clock::now(); + double ready = print("wait_for when ready", stop - start); + + // polling before ready with wait_for(0s) should be almost as fast as + // after the result is ready. + VERIFY( wait_for_0 < (ready * 10) ); + + // The following two tests fail with GCC 11, see + // https://gcc.gnu.org/pipermail/libstdc++/2020-November/051422.html +#if 0 + // polling before ready using wait_until(epoch) should not be terribly slow. + VERIFY( wait_until_sys_epoch < (ready * 100) ); + VERIFY( wait_until_steady_epoch < (ready * 100) ); +#endif + + // polling before ready using wait_until(min) should not be terribly slow. + VERIFY( wait_until_sys_min < (ready * 100) ); + VERIFY( wait_until_steady_min < (ready * 100) ); +} |