[PATCH] Cygwin: thread: Allow fast_mutex to be acquired multiple times.

[Jeremy Drake]

On Sun, 6 Apr 2025, Takashi Yano wrote:

> Revised.

Sorry to be late to the party (I didn't open the attachment before, and
only saw the commit):

> +  static class keys_list {
> +    LONG64 seq;
> +    LONG64 busy_cnt;

Should these be `volatile`?  busy_cnt is probably OK, it only seems to be
dealt with via Interlocked functions, but seq is tested directly in some
cases and via Interlocked in others.