smeenai added inline comments.
================
Comment at: include/__threading_support:300-305
+int __libcpp_recursive_mutex_init(__libcpp_mutex_t *__m)
+{
+ InitializeSRWLock(__m);
+ return 0;
+}
+
----------------
majnemer wrote:
> compnerd wrote:
> > majnemer wrote:
> > > I don't think you can use slim rw locks for recursive locks. I think we
> > > will need to use `CRITICAL_SECTION` for those. std::recursive_mutex can't
> > > be used with std::condition_variable AFAIK so all you need (I think) is
> > > recursive versions of `__libcpp_mutex_...`
> > >
> > > Recursive locks should be used far less frequently which makes it
> > > valuable, IMO, to use slim rw locks for the non-recursive mutex
> > > implementation.
> > You are absolutely right. That was something that I looked at originally
> > and went with the CS. However, the overhead of a tagged struct is 5 or 9
> > bytes (sizeof(void *) + 1) bytes (ignoring padding for MS ABI). Going with
> > that should give the benefits of always being able to properly initialize
> > the CS instead of the kludge.
> Er, isn't the overhead much more than that? IIRC, `CRITICAL_SECTION` is quite
> large. You'd be making all the users of `std::mutex` pay for the space of
> `std::recursive_mutex`...
Yeah, CRITICAL_SECTION is 24 bytes vs 4 bytes for a SRWLOCK.
Repository:
rL LLVM
https://reviews.llvm.org/D28220
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