[PATCH 2/2] manual: Document __libc_single_threaded

[Florian Weimer]

* Szabolcs Nagy:

> The 05/21/2020 15:44, Florian Weimer wrote:
>> * Szabolcs Nagy:
>> > what's wrong with pthread_join updating it?
>> 
>> It's tricky do it correctly if there are two remaining threads, one of
>> them the one being joined, the other one a detached thread.  A
>> straightforward implementation merely looking at __nptl_nthreads before
>> returning from pthread_join would not perform the required
>> synchronization on the detached thread exit.
>
> i'm trying to understand this, but don't see
> what's wrong if the last thread is detached.

Sorry, I meant three reamining threads in total, i.e., two more threads
in addition to the one thread that keeps going after the other two
exited, and may use __libc_single_threaded in the future.

Clearer now?

Thanks,
Florian