[libcxx-commits] [libcxx] [libc++] debug semaaphore (PR #180353)
via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Feb 11 06:24:04 PST 2026
https://github.com/huixie90 updated https://github.com/llvm/llvm-project/pull/180353
>From 79cc6e2cc0b253b0a34a3b5ad302341fa943170b Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Sat, 7 Feb 2026 16:19:16 +0000
Subject: [PATCH 1/8] [libc++] debug semaaphore
---
.../thread.semaphore/timed.debug.pass.cpp | 84 +++++++++++++++++++
1 file changed, 84 insertions(+)
create mode 100644 libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
new file mode 100644
index 0000000000000..d7833194927e4
--- /dev/null
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -0,0 +1,84 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <semaphore>
+
+#include <semaphore>
+#include <thread>
+#include <chrono>
+#include <cassert>
+#include <iostream>
+#include <iomanip>
+
+
+#include "make_test_thread.h"
+#include "test_macros.h"
+
+int main(int, char**)
+{
+ auto const start = std::chrono::steady_clock::now();
+ auto log = [start] ()-> auto& {
+ using namespace std::chrono;
+
+ auto elapsed = steady_clock::now() - start;
+
+ auto hours = duration_cast<std::chrono::hours>(elapsed);
+ elapsed -= hours;
+
+ auto minutes = duration_cast<std::chrono::minutes>(elapsed);
+ elapsed -= minutes;
+
+ auto seconds = duration_cast<std::chrono::seconds>(elapsed);
+ elapsed -= seconds;
+
+ auto milliseconds = duration_cast<std::chrono::milliseconds>(elapsed);
+
+ std::cerr << "["
+ << std::setw(2) << std::setfill('0') << hours.count() << ":"
+ << std::setw(2) << std::setfill('0') << minutes.count() << ":"
+ << std::setw(2) << std::setfill('0') << seconds.count() << "."
+ << std::setw(3) << std::setfill('0') << milliseconds.count()
+ << "] ";
+
+ return std::cerr;
+ };
+
+ std::counting_semaphore<> s(0);
+
+ log() << "try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
+ assert(!s.try_acquire_until(start + std::chrono::milliseconds(250)));
+ log() << "done: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
+
+ log() << "try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
+ assert(!s.try_acquire_for(std::chrono::milliseconds(250)));
+ log() << "done: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
+
+ std::thread t = support::make_test_thread([&](){
+ std::this_thread::sleep_for(std::chrono::milliseconds(250));
+ s.release();
+ std::this_thread::sleep_for(std::chrono::milliseconds(250));
+ s.release();
+ });
+
+ log() << "try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
+ assert(s.try_acquire_until(start + std::chrono::seconds(2)));
+ log() << "done: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
+
+ log() << "try_acquire_for: " << std::chrono::seconds(2) << "\n";
+ assert(s.try_acquire_for(std::chrono::seconds(2)));
+ log() << "done: try_acquire_for: " << std::chrono::seconds(2) << "\n";
+ t.join();
+
+ auto const end = std::chrono::steady_clock::now();
+ assert(end - start < std::chrono::seconds(10));
+
+ return 1;
+}
>From 15caf8d017581b2ac398c6e89c3b9bd9cb81180d Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Sat, 7 Feb 2026 16:23:48 +0000
Subject: [PATCH 2/8] code to debug
---
.../thread.semaphore/timed.debug.pass.cpp | 34 ++++++++++++-------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index d7833194927e4..904da25a49940 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -22,13 +22,11 @@
#include "make_test_thread.h"
#include "test_macros.h"
-int main(int, char**)
-{
- auto const start = std::chrono::steady_clock::now();
- auto log = [start] ()-> auto& {
+void test(auto log_start){
+ auto log = [log_start] ()-> auto& {
using namespace std::chrono;
- auto elapsed = steady_clock::now() - start;
+ auto elapsed = steady_clock::now() - log_start;
auto hours = duration_cast<std::chrono::hours>(elapsed);
elapsed -= hours;
@@ -51,15 +49,16 @@ int main(int, char**)
return std::cerr;
};
+ auto const start = std::chrono::steady_clock::now();
std::counting_semaphore<> s(0);
- log() << "try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
+ log() << "start: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
assert(!s.try_acquire_until(start + std::chrono::milliseconds(250)));
- log() << "done: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
+ log() << "done: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
- log() << "try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
+ log() << "start: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
assert(!s.try_acquire_for(std::chrono::milliseconds(250)));
- log() << "done: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
+ log() << "done: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
std::thread t = support::make_test_thread([&](){
std::this_thread::sleep_for(std::chrono::milliseconds(250));
@@ -68,17 +67,26 @@ int main(int, char**)
s.release();
});
- log() << "try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
+ log() << "start: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
assert(s.try_acquire_until(start + std::chrono::seconds(2)));
- log() << "done: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
+ log() << "done: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
- log() << "try_acquire_for: " << std::chrono::seconds(2) << "\n";
+ log() << "start: try_acquire_for: " << std::chrono::seconds(2) << "\n";
assert(s.try_acquire_for(std::chrono::seconds(2)));
- log() << "done: try_acquire_for: " << std::chrono::seconds(2) << "\n";
+ log() << "done: try_acquire_for: " << std::chrono::seconds(2) << "\n";
t.join();
auto const end = std::chrono::steady_clock::now();
assert(end - start < std::chrono::seconds(10));
+}
+
+int main(int, char**)
+{
+ auto const log_start = std::chrono::steady_clock::now();
+ for (auto i = 0; i < 10; ++i) {
+ std::cerr << "=== Iteration " << i << " ===\n";
+ test(log_start);
+ }
return 1;
}
>From 09616457c9c0868806e5a3735ca9706f963e6066 Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Sat, 7 Feb 2026 16:44:11 +0000
Subject: [PATCH 3/8] stage3
---
libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index 904da25a49940..d032145f9824d 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -88,5 +88,10 @@ int main(int, char**)
test(log_start);
}
+#if defined(_WIN32)
return 1;
+#else
+ return 0;
+#endif
+
}
>From d77abc88ea2e0255caf69a682ef7dd896e1dca56 Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Sun, 8 Feb 2026 08:39:09 +0000
Subject: [PATCH 4/8] debug small
---
.../thread.semaphore/timed.debug.pass.cpp | 39 ++++++-------------
1 file changed, 12 insertions(+), 27 deletions(-)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index d032145f9824d..0294d1fef680d 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -37,13 +37,13 @@ void test(auto log_start){
auto seconds = duration_cast<std::chrono::seconds>(elapsed);
elapsed -= seconds;
- auto milliseconds = duration_cast<std::chrono::milliseconds>(elapsed);
+ auto nanoseconds = duration_cast<std::chrono::nanoseconds>(elapsed);
std::cerr << "["
<< std::setw(2) << std::setfill('0') << hours.count() << ":"
<< std::setw(2) << std::setfill('0') << minutes.count() << ":"
<< std::setw(2) << std::setfill('0') << seconds.count() << "."
- << std::setw(3) << std::setfill('0') << milliseconds.count()
+ << std::setw(9) << std::setfill('0') << nanoseconds.count()
<< "] ";
return std::cerr;
@@ -52,29 +52,18 @@ void test(auto log_start){
auto const start = std::chrono::steady_clock::now();
std::counting_semaphore<> s(0);
- log() << "start: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
- assert(!s.try_acquire_until(start + std::chrono::milliseconds(250)));
- log() << "done: try_acquire_until: start + " << std::chrono::milliseconds(250) << "\n";
+ log() << "start: try_acquire_for: " << std::chrono::nanoseconds(1) << "\n";
+ assert(!s.try_acquire_for(std::chrono::nanoseconds(1)));
+ log() << "done: try_acquire_for: " << std::chrono::nanoseconds(1) << "\n";
- log() << "start: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
- assert(!s.try_acquire_for(std::chrono::milliseconds(250)));
- log() << "done: try_acquire_for: " << std::chrono::milliseconds(250) << "\n";
+ log() << "start: try_acquire_for: " << std::chrono::microseconds(1) << "\n";
+ assert(!s.try_acquire_for(std::chrono::microseconds(1)));
+ log() << "done: try_acquire_for: " << std::chrono::microseconds(1) << "\n";
- std::thread t = support::make_test_thread([&](){
- std::this_thread::sleep_for(std::chrono::milliseconds(250));
- s.release();
- std::this_thread::sleep_for(std::chrono::milliseconds(250));
- s.release();
- });
+ log() << "start: try_acquire_for: " << std::chrono::milliseconds(1) << "\n";
+ assert(!s.try_acquire_for(std::chrono::milliseconds(1)));
+ log() << "done: try_acquire_for: " << std::chrono::milliseconds(1) << "\n";
- log() << "start: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
- assert(s.try_acquire_until(start + std::chrono::seconds(2)));
- log() << "done: try_acquire_until: start + " << std::chrono::seconds(2) << "\n";
-
- log() << "start: try_acquire_for: " << std::chrono::seconds(2) << "\n";
- assert(s.try_acquire_for(std::chrono::seconds(2)));
- log() << "done: try_acquire_for: " << std::chrono::seconds(2) << "\n";
- t.join();
auto const end = std::chrono::steady_clock::now();
assert(end - start < std::chrono::seconds(10));
@@ -83,15 +72,11 @@ void test(auto log_start){
int main(int, char**)
{
auto const log_start = std::chrono::steady_clock::now();
- for (auto i = 0; i < 10; ++i) {
+ for (auto i = 0; i < 100; ++i) {
std::cerr << "=== Iteration " << i << " ===\n";
test(log_start);
}
-#if defined(_WIN32)
- return 1;
-#else
return 0;
-#endif
}
>From 93cace578c2f07f0ce642ac5deb664074c056025 Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Wed, 11 Feb 2026 08:58:27 +0000
Subject: [PATCH 5/8] debug
---
libcxx/include/__thread/poll_with_backoff.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/libcxx/include/__thread/poll_with_backoff.h b/libcxx/include/__thread/poll_with_backoff.h
index e007e7746ca52..d47ca90c663f4 100644
--- a/libcxx/include/__thread/poll_with_backoff.h
+++ b/libcxx/include/__thread/poll_with_backoff.h
@@ -13,6 +13,8 @@
#include <__chrono/duration.h>
#include <__chrono/high_resolution_clock.h>
#include <__config>
+ #include <cstdio>
+
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -59,7 +61,9 @@ _LIBCPP_HIDE_FROM_ABI __poll_with_backoff_results __libcpp_thread_poll_with_back
__count += 1;
continue;
}
- chrono::nanoseconds const __elapsed = chrono::high_resolution_clock::now() - __start;
+ auto __now = chrono::high_resolution_clock::now();
+ chrono::nanoseconds const __elapsed = __now - __start;
+ std::fprintf(stderr, "start: %lld ns\nnow: %lld ns\nelapsed: %lld ns\n", __start.time_since_epoch().count(), __now.time_since_epoch().count(), __elapsed.count());
if (__max_elapsed != chrono::nanoseconds::zero() && __max_elapsed < __elapsed)
return __poll_with_backoff_results::__timeout;
if (auto __backoff_res = __backoff(__elapsed); __backoff_res == __backoff_results::__continue_poll)
>From 4101ae47509675e6298a2ff7acb038292b6a71ba Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Wed, 11 Feb 2026 10:00:13 +0000
Subject: [PATCH 6/8] debug
---
libcxx/include/__thread/poll_with_backoff.h | 4 ++++
libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp | 4 +++-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/libcxx/include/__thread/poll_with_backoff.h b/libcxx/include/__thread/poll_with_backoff.h
index d47ca90c663f4..e9fd784a25674 100644
--- a/libcxx/include/__thread/poll_with_backoff.h
+++ b/libcxx/include/__thread/poll_with_backoff.h
@@ -13,7 +13,9 @@
#include <__chrono/duration.h>
#include <__chrono/high_resolution_clock.h>
#include <__config>
+ #if defined (TEST_DEBUG)
#include <cstdio>
+ #endif
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -63,7 +65,9 @@ _LIBCPP_HIDE_FROM_ABI __poll_with_backoff_results __libcpp_thread_poll_with_back
}
auto __now = chrono::high_resolution_clock::now();
chrono::nanoseconds const __elapsed = __now - __start;
+ #if defined (TEST_DEBUG)
std::fprintf(stderr, "start: %lld ns\nnow: %lld ns\nelapsed: %lld ns\n", __start.time_since_epoch().count(), __now.time_since_epoch().count(), __elapsed.count());
+ #endif
if (__max_elapsed != chrono::nanoseconds::zero() && __max_elapsed < __elapsed)
return __poll_with_backoff_results::__timeout;
if (auto __backoff_res = __backoff(__elapsed); __backoff_res == __backoff_results::__continue_poll)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index 0294d1fef680d..96d10e02b4986 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -8,9 +8,11 @@
//
// UNSUPPORTED: no-threads
// UNSUPPORTED: c++03, c++11, c++14, c++17
+// ADDITIONAL_COMPILE_FLAGS: -DTEST_DEBUG
// <semaphore>
+
#include <semaphore>
#include <thread>
#include <chrono>
@@ -77,6 +79,6 @@ int main(int, char**)
test(log_start);
}
- return 0;
+ return 1;
}
>From b35dcaec5023c6fbbc016cd71970b434a3277349 Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Wed, 11 Feb 2026 12:16:00 +0000
Subject: [PATCH 7/8] ci
---
libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index 96d10e02b4986..42c34a38362d3 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -79,6 +79,6 @@ int main(int, char**)
test(log_start);
}
- return 1;
+ return 0;
}
>From 445005b75528ec845aaf59ba7017b06bdcd2cfdb Mon Sep 17 00:00:00 2001
From: Hui Xie <hui.xie1990 at gmail.com>
Date: Wed, 11 Feb 2026 14:23:47 +0000
Subject: [PATCH 8/8] timed
---
.../thread.semaphore/timed.debug.pass.cpp | 24 ++++++++-----------
1 file changed, 10 insertions(+), 14 deletions(-)
diff --git a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
index 42c34a38362d3..eef5dfb698295 100644
--- a/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
+++ b/libcxx/test/std/thread/thread.semaphore/timed.debug.pass.cpp
@@ -12,7 +12,6 @@
// <semaphore>
-
#include <semaphore>
#include <thread>
#include <chrono>
@@ -20,12 +19,11 @@
#include <iostream>
#include <iomanip>
-
#include "make_test_thread.h"
#include "test_macros.h"
-void test(auto log_start){
- auto log = [log_start] ()-> auto& {
+void test(auto log_start) {
+ auto log = [log_start]() -> auto& {
using namespace std::chrono;
auto elapsed = steady_clock::now() - log_start;
@@ -41,12 +39,9 @@ void test(auto log_start){
auto nanoseconds = duration_cast<std::chrono::nanoseconds>(elapsed);
- std::cerr << "["
- << std::setw(2) << std::setfill('0') << hours.count() << ":"
- << std::setw(2) << std::setfill('0') << minutes.count() << ":"
- << std::setw(2) << std::setfill('0') << seconds.count() << "."
- << std::setw(9) << std::setfill('0') << nanoseconds.count()
- << "] ";
+ std::cerr << "[" << std::setw(2) << std::setfill('0') << hours.count() << ":" << std::setw(2) << std::setfill('0')
+ << minutes.count() << ":" << std::setw(2) << std::setfill('0') << seconds.count() << "." << std::setw(9)
+ << std::setfill('0') << nanoseconds.count() << "] ";
return std::cerr;
};
@@ -66,19 +61,20 @@ void test(auto log_start){
assert(!s.try_acquire_for(std::chrono::milliseconds(1)));
log() << "done: try_acquire_for: " << std::chrono::milliseconds(1) << "\n";
-
auto const end = std::chrono::steady_clock::now();
assert(end - start < std::chrono::seconds(10));
}
-int main(int, char**)
-{
+int main(int, char**) {
auto const log_start = std::chrono::steady_clock::now();
for (auto i = 0; i < 100; ++i) {
std::cerr << "=== Iteration " << i << " ===\n";
test(log_start);
}
+#if defined(_WIN32)
+ return 1;
+#else
return 0;
-
+#endif
}
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