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libcxx: Implement atomic::wait/notify using _umtx_op(2) for 64bit arches

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Only 64bit architectures can be supported this way, because libcxx
defines __cxx_contention_t to be int64_t for FreeBSD, and 32bit arches
do not have a kind of UMTX_OP_WAIT_INT64_PRIVATE operation.

LLVM review:	https://reviews.llvm.org/D142134

Tested by:	emaste
Reviewed by:	dim, emaste, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D38132
This commit is contained in:
Konstantin Belousov 2023-01-20 04:57:26 +02:00
parent 62adb1e953
commit 9c996882b0
1 changed files with 21 additions and 0 deletions
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21
contrib/llvm-project/libcxx/src/atomic.cpp
View File

@ -26,6 +26,11 @@
# define SYS_futex SYS_futex_time64
#endif
#elif defined(__FreeBSD__)
#include <sys/types.h>
#include <sys/umtx.h>
#else // <- Add other operating systems here
// Baseline needs no new headers
@ -72,6 +77,22 @@ static void __libcpp_platform_wake_by_address(__cxx_atomic_contention_t const vo
const_cast<__cxx_atomic_contention_t*>(__ptr), 0);
}
#elif defined(__FreeBSD__) && defined(__LP64__)
static void __libcpp_platform_wait_on_address(__cxx_atomic_contention_t const volatile* __ptr,
__cxx_contention_t __val)
{
_umtx_op(const_cast<__cxx_atomic_contention_t*>(__ptr),
UMTX_OP_WAIT, __val, NULL, NULL);
}
static void __libcpp_platform_wake_by_address(__cxx_atomic_contention_t const volatile* __ptr,
bool __notify_one)
{
_umtx_op(const_cast<__cxx_atomic_contention_t*>(__ptr),
UMTX_OP_WAKE, __notify_one ? 1 : INT_MAX, NULL, NULL);
}
#else // <- Add other operating systems here
// Baseline is just a timed backoff