I agree with this change. On Thu, Jan 5, 2023 at 4:22 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> How about this? > > I don't think we should worry about targets without atomic int, so don't > bother using types smaller than int. > > > -- >8 -- > > For non-futex targets the __platform_wait_t type is currently uint64_t, > but that requires a lock in libatomic for some 32-bit targets. We don't > really need a 64-bit type, so use unsigned long if that is lock-free, > and int otherwise. This should mean it's lock-free on a wider set of > targets. > > libstdc++-v3/ChangeLog: > > * include/bits/atomic_wait.h (__detail::__platform_wait_t): > Define as unsigned long if always lock-free, and unsigned int > otherwise. > --- > libstdc++-v3/include/bits/atomic_wait.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/libstdc++-v3/include/bits/atomic_wait.h > b/libstdc++-v3/include/bits/atomic_wait.h > index bd1ed56d157..46f39f10cbc 100644 > --- a/libstdc++-v3/include/bits/atomic_wait.h > +++ b/libstdc++-v3/include/bits/atomic_wait.h > @@ -64,7 +64,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > // and __platform_notify() if there is a more efficient primitive > supported > // by the platform (e.g. __ulock_wait()/__ulock_wake()) which is better > than > // a mutex/condvar based wait. > - using __platform_wait_t = uint64_t; > +# if ATOMIC_LONG_LOCK_FREE == 2 > + using __platform_wait_t = unsigned long; > +# else > + using __platform_wait_t = unsigned int; > +# endif > inline constexpr size_t __platform_wait_alignment > = __alignof__(__platform_wait_t); > #endif > -- > 2.39.0 > >
