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[libstdc++] Fix test timeout in stop_calback/destroy.cc

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A change was made to __atomic_semaphore::_S_do_try_acquire() to
(ideally) let the compare_exchange reload the value of __old rather than
always reloading it twice. This causes _M_acquire to spin indefinitely
if the value of __old is already 0.

libstdc++-v3/ChangeLog:
	* include/bits/semaphore_base.h: Always reload __old in
	__atomic_semaphore::_S_do_try_acquire().
	* testsuite/30_threads/stop_token/stop_callback/destroy.cc:
	re-enable testcase.
This commit is contained in:
Thomas Rodgers 2021-04-21 10:01:06 -07:00
parent a44895ce7f
commit 7eeb8c04e5
2 changed files with 6 additions and 12 deletions
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16
libstdc++-v3/include/bits/semaphore_base.h
View file

@ -196,9 +196,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__atomic_semaphore& operator=(const __atomic_semaphore&) = delete;
static _GLIBCXX_ALWAYS_INLINE bool
_S_do_try_acquire(__detail::__platform_wait_t* __counter,
__detail::__platform_wait_t& __old) noexcept
_S_do_try_acquire(__detail::__platform_wait_t* __counter) noexcept
{
auto __old = __atomic_impl::load(__counter, memory_order::acquire);
if (__old == 0)
return false;
@ -211,18 +211,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_ALWAYS_INLINE void
_M_acquire() noexcept
{
auto __old = __atomic_impl::load(&_M_counter, memory_order::acquire);
auto const __pred =
[this, &__old] { return _S_do_try_acquire(&this->_M_counter, __old); };
[this] { return _S_do_try_acquire(&this->_M_counter); };
std::__atomic_wait_address_bare(&_M_counter, __pred);
}
bool
_M_try_acquire() noexcept
{
auto __old = __atomic_impl::load(&_M_counter, memory_order::acquire);
auto const __pred =
[this, &__old] { return _S_do_try_acquire(&this->_M_counter, __old); };
[this] { return _S_do_try_acquire(&this->_M_counter); };
return std::__detail::__atomic_spin(__pred);
}
@ -231,9 +229,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_try_acquire_until(const chrono::time_point<_Clock,
_Duration>& __atime) noexcept
{
auto __old = __atomic_impl::load(&_M_counter, memory_order_relaxed);
auto const __pred =
[this, &__old] { return _S_do_try_acquire(&this->_M_counter, __old); };
[this] { return _S_do_try_acquire(&this->_M_counter); };
return __atomic_wait_address_until_bare(&_M_counter, __pred, __atime);
}
@ -243,9 +240,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_try_acquire_for(const chrono::duration<_Rep, _Period>& __rtime)
noexcept
{
auto __old = __atomic_impl::load(&_M_counter, memory_order_relaxed);
auto const __pred =
[this, &__old] { return _S_do_try_acquire(&this->_M_counter, __old); };
[this] { return _S_do_try_acquire(&this->_M_counter); };
return __atomic_wait_address_for_bare(&_M_counter, __pred, __rtime);
}

2
libstdc++-v3/testsuite/30_threads/stop_token/stop_callback/destroy.cc
View file

@ -21,8 +21,6 @@
// { dg-require-effective-target pthread }
// { dg-require-gthreads "" }
// { dg-skip-if "FIXME: times out" { *-*-* } }
#include <stop_token>
#include <atomic>
#include <thread>