public inbox for libstdc++-cvs@sourceware.org help / color / mirror / Atom feed
From: Thomas Rodgers <rodgertq@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-1732] libstdc++: Fix for deadlock in std::counting_semaphore [PR100806] Date: Tue, 22 Jun 2021 18:07:06 +0000 (GMT) [thread overview] Message-ID: <20210622180706.69AF33858023@sourceware.org> (raw) https://gcc.gnu.org/g:e02840c1a92abecd211ffaf05b28329bcb534583 commit r12-1732-ge02840c1a92abecd211ffaf05b28329bcb534583 Author: Thomas Rodgers <rodgert@appliantology.com> Date: Tue Jun 22 10:59:07 2021 -0700 libstdc++: Fix for deadlock in std::counting_semaphore [PR100806] libstdc++-v3/ChangeLog: PR libstdc++/100806 * include/bits/semaphore_base.h (__atomic_semaphore::_M_release): Force _M_release() to wake all waiting threads. * testsuite/30_threads/semaphore/100806.cc: New test. Diff: --- libstdc++-v3/include/bits/semaphore_base.h | 4 +- .../testsuite/30_threads/semaphore/100806.cc | 57 ++++++++++++++++++++++ 2 files changed, 60 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/semaphore_base.h b/libstdc++-v3/include/bits/semaphore_base.h index 9a55978068f..c4565d7e560 100644 --- a/libstdc++-v3/include/bits/semaphore_base.h +++ b/libstdc++-v3/include/bits/semaphore_base.h @@ -256,7 +256,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if (__update > 1) __atomic_notify_address_bare(&_M_counter, true); else - __atomic_notify_address_bare(&_M_counter, false); + __atomic_notify_address_bare(&_M_counter, true); +// FIXME - Figure out why this does not wake a waiting thread +// __atomic_notify_address_bare(&_M_counter, false); } private: diff --git a/libstdc++-v3/testsuite/30_threads/semaphore/100806.cc b/libstdc++-v3/testsuite/30_threads/semaphore/100806.cc new file mode 100644 index 00000000000..2fa2628a278 --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/semaphore/100806.cc @@ -0,0 +1,57 @@ +// { dg-options "-std=gnu++2a -pthread" } +// { dg-do run { target c++2a } } +// { dg-require-effective-target pthread } +// { dg-require-gthreads "" } +// { dg-add-options libatomic } + +#include <iostream> +#include <sstream> + +#include <thread> +#include <semaphore> +#include <mutex> +#include <chrono> +#include <vector> + +std::counting_semaphore<4> semaphore{6}; + +std::mutex mtx; +std::vector<std::string> results; + +void thread_main(size_t x) +{ + semaphore.acquire(); + std::this_thread::sleep_for(std::chrono::milliseconds(100)); + semaphore.release(); + { + std::ostringstream stm; + stm << "Thread " << x << " finished."; + std::lock_guard g{ mtx }; + results.push_back(stm.str()); + } +} + +int main() +{ + constexpr auto nthreads = 10; + + std::vector<std::thread> threads(nthreads); + + size_t counter{0}; + for(auto& t : threads) + { + t = std::thread(thread_main, counter++); + } + + for(auto& t : threads) + { + t.join(); + { + std::lock_guard g{ mtx }; + for (auto&& r : results) + std::cout << r << '\n'; + std::cout.flush(); + results.clear(); + } + } +}
reply other threads:[~2021-06-22 18:07 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20210622180706.69AF33858023@sourceware.org \ --to=rodgertq@gcc.gnu.org \ --cc=gcc-cvs@gcc.gnu.org \ --cc=libstdc++-cvs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).