From 9e18a25331fa25c3907249fede65a02c6817b06e Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 7 Dec 2021 15:11:15 +0000 Subject: [PATCH] libstdc++: Allow std::condition_variable waits to be cancelled [PR103382] std::condition_variable::wait(unique_lock&) is incorrectly marked noexcept, which means that the __forced_unwind exception used by NPTL cancellation will terminate the process. It should allow exceptions to pass through, so that a thread can be cleanly cancelled when waiting on a condition variable. The new behaviour is exported as a new version of the symbol, to avoid an ABI break for existing code linked to the non-throwing definition of the function. Code linked against older releases will have a reference to the @GLIBCXX_3.4.11 version, andcode compiled against the new libstdc++ will get a reference to the @@GLIBCXX_3.4.30 version. libstdc++-v3/ChangeLog: PR libstdc++/103382 * config/abi/pre/gnu.ver (GLIBCXX_3.4.11): Do not export old symbol if .symver renaming is supported. (GLIBCXX_3.4.30): Export new symbol if .symver renaming is supported. * doc/xml/manual/evolution.xml: Document change. * doc/html/manual/api.html: Regenerate. * include/bits/std_mutex.h (__condvar::wait, __condvar::wait_until): Remove noexcept. * include/std/condition_variable (condition_variable::wait): Likewise. * src/c++11/condition_variable.cc (condition_variable::wait): Likewise. * src/c++11/compatibility-condvar.cc (__nothrow_wait_cv::wait): Define nothrow wrapper around std::condition_variable::wait and export the old symbol as an alias to it. * testsuite/30_threads/condition_variable/members/103382.cc: New test. --- libstdc++-v3/config/abi/pre/gnu.ver | 12 +++- libstdc++-v3/doc/html/manual/api.html | 5 ++ libstdc++-v3/doc/xml/manual/evolution.xml | 7 ++ libstdc++-v3/include/bits/std_mutex.h | 6 +- libstdc++-v3/include/std/condition_variable | 2 +- .../src/c++11/compatibility-condvar.cc | 31 +++++++++ libstdc++-v3/src/c++11/condition_variable.cc | 2 +- .../condition_variable/members/103382.cc | 66 +++++++++++++++++++ 8 files changed, 125 insertions(+), 6 deletions(-) create mode 100644 libstdc++-v3/testsuite/30_threads/condition_variable/members/103382.cc diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver index 8f3c7b3827ea..b747351a1b98 100644 --- a/libstdc++-v3/config/abi/pre/gnu.ver +++ b/libstdc++-v3/config/abi/pre/gnu.ver @@ -1285,7 +1285,6 @@ GLIBCXX_3.4.11 { # condition_variable _ZNSt18condition_variable10notify_allEv; _ZNSt18condition_variable10notify_oneEv; - _ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE; _ZNSt18condition_variableC1Ev; _ZNSt18condition_variableC2Ev; _ZNSt18condition_variableD1Ev; @@ -1295,6 +1294,12 @@ GLIBCXX_3.4.11 { _ZNSt22condition_variable_anyD1Ev; _ZNSt22condition_variable_anyD2Ev; +#ifndef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT + # The original definition of this symbol gets versioned as @GLIBCXX_3.4.11 + # if ".symver" is supported, or as @@GLIBCXX_3.4.11 otherwise. + _ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE; +#endif + # thread _ZNSt6thread4joinEv; _ZNSt6thread6detachEv; @@ -2401,6 +2406,11 @@ GLIBCXX_3.4.30 { _ZSt21__glibcxx_assert_fail*; +#ifdef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT + # The new definition of this symbol gets versioned as @@GLIBCXX_3.4.30 + _ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE; +#endif + } GLIBCXX_3.4.29; # Symbols in the support library (libsupc++) have their own tag. diff --git a/libstdc++-v3/doc/html/manual/api.html b/libstdc++-v3/doc/html/manual/api.html index 00701fa1044c..1c7fdaa7394c 100644 --- a/libstdc++-v3/doc/html/manual/api.html +++ b/libstdc++-v3/doc/html/manual/api.html @@ -450,4 +450,9 @@ options for --enable-libstdcxx-allocator were remove For the new option, std::allocator no longer derives from __gnu_cxx::new_allocator; they both derive from std::__new_allocator instead. +

+std::condition_variable::wait changed to be +noexcept(false) to allow thread cancellation exceptions to +be thrown from pthread_cond_wait without aborting +the process.

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\ No newline at end of file diff --git a/libstdc++-v3/doc/xml/manual/evolution.xml b/libstdc++-v3/doc/xml/manual/evolution.xml index a169102ef430..34e44ee93e40 100644 --- a/libstdc++-v3/doc/xml/manual/evolution.xml +++ b/libstdc++-v3/doc/xml/manual/evolution.xml @@ -1041,6 +1041,13 @@ no longer derives from __gnu_cxx::new_allocator; they both derive from std::__new_allocator instead. + +std::condition_variable::wait changed to be +noexcept(false) to allow thread cancellation exceptions to +be thrown from pthread_cond_wait without aborting +the process. + + diff --git a/libstdc++-v3/include/bits/std_mutex.h b/libstdc++-v3/include/bits/std_mutex.h index 357c68914389..6618a54396f5 100644 --- a/libstdc++-v3/include/bits/std_mutex.h +++ b/libstdc++-v3/include/bits/std_mutex.h @@ -149,7 +149,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Expects: Calling thread has locked __m. void - wait(mutex& __m) noexcept + wait(mutex& __m) { int __e __attribute__((__unused__)) = __gthread_cond_wait(&_M_cond, __m.native_handle()); @@ -157,14 +157,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } void - wait_until(mutex& __m, timespec& __abs_time) noexcept + wait_until(mutex& __m, timespec& __abs_time) { __gthread_cond_timedwait(&_M_cond, __m.native_handle(), &__abs_time); } #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT void - wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time) noexcept + wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time) { pthread_cond_clockwait(&_M_cond, __m.native_handle(), __clock, &__abs_time); diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable index 4fcec6aa73d2..3930cf487e96 100644 --- a/libstdc++-v3/include/std/condition_variable +++ b/libstdc++-v3/include/std/condition_variable @@ -92,7 +92,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION notify_all() noexcept; void - wait(unique_lock& __lock) noexcept; + wait(unique_lock& __lock); template void diff --git a/libstdc++-v3/src/c++11/compatibility-condvar.cc b/libstdc++-v3/src/c++11/compatibility-condvar.cc index 575d78055cb6..07c39d48f5ac 100644 --- a/libstdc++-v3/src/c++11/compatibility-condvar.cc +++ b/libstdc++-v3/src/c++11/compatibility-condvar.cc @@ -54,4 +54,35 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_END_NAMESPACE_VERSION } // namespace std +#if ! _GLIBCXX_INLINE_VERSION +// XXX GLIBCXX_ABI Deprecated +// gcc-12.1 +// std::condition_variable::wait changed to noexcept(false) +#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \ + && defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE) \ + && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT) +namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) +{ +struct __nothrow_wait_cv : std::condition_variable +{ + void wait(std::unique_lock&) noexcept; +}; + +__attribute__((used)) +void +__nothrow_wait_cv::wait(std::unique_lock& lock) noexcept +{ + this->condition_variable::wait(lock); +} +} // namespace __gnu_cxx + +// Export a noexcept wrapper around std::condition_variable::wait +// with the original @GLIBCXX_3.4.11 symbol version. +asm( + ".symver _ZN9__gnu_cxx17__nothrow_wait_cv4waitERSt11unique_lockISt5mutexE," + "_ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE@GLIBCXX_3.4.11" +); +#endif +#endif + #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1 diff --git a/libstdc++-v3/src/c++11/condition_variable.cc b/libstdc++-v3/src/c++11/condition_variable.cc index ca7902e03735..2d7b8a19b9d6 100644 --- a/libstdc++-v3/src/c++11/condition_variable.cc +++ b/libstdc++-v3/src/c++11/condition_variable.cc @@ -36,7 +36,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION condition_variable::~condition_variable() noexcept = default; void - condition_variable::wait(unique_lock& __lock) noexcept + condition_variable::wait(unique_lock& __lock) { _M_cond.wait(*__lock.mutex()); } diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/103382.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/103382.cc new file mode 100644 index 000000000000..67396ebf323b --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/103382.cc @@ -0,0 +1,66 @@ +// { dg-options "-pthread" } +// { dg-do run { target { *-*-linux* *-*-gnu* } } } +// { dg-require-effective-target c++11 } +// { dg-require-effective-target pthread } +// { dg-require-gthreads "" } + +#include +#include +#include +#include + +// PR libstdc++/103382 + +template +void +test_cancel(F wait) +{ + std::mutex m; + std::condition_variable cv; + bool waiting = false; + + std::thread t([&] { + std::unique_lock lock(m); + waiting = true; + wait(cv, lock); // __forced_unwind exception should not terminate process. + }); + + // Ensure the condition variable is waiting before we cancel. + // This shouldn't be necessary because pthread_mutex_lock is not + // a cancellation point, but no harm in making sure we test what + // we intend to test: that cancel during a wait doesn't abort. + while (true) + { + std::unique_lock lock(m); + if (waiting) + break; + } + + pthread_cancel(t.native_handle()); + t.join(); +} + +int main() +{ + test_cancel( + [](std::condition_variable& cv, std::unique_lock& l) { + cv.wait(l); + }); + + test_cancel( + [](std::condition_variable& cv, std::unique_lock& l) { + cv.wait(l, []{ return false; }); + }); + + using mins = std::chrono::minutes; + + test_cancel( + [](std::condition_variable& cv, std::unique_lock& l) { + cv.wait_for(l, mins(1)); + }); + + test_cancel( + [](std::condition_variable& cv, std::unique_lock& l) { + cv.wait_until(l, std::chrono::system_clock::now() + mins(1)); + }); +} -- 2.47.2