pthread_cancel and EH: let's try this again

[Alexander Terekhov]

Nathan Sidwell wrote:
[...]
> It's also not clear to me how one would implement the necessary 
> delay to retrying the thread cancellation until one had returned 
> from the nothrow function.

You mean another cancellation point (async cancel regions aside 
for a moment) in the "same" dynamic context with unexpected 
cancellation exception? Even without any optimizations, that 
overhead of repetitive search is not a big deal since it would 
occur only when cancellation request is pending.

regards,
alexander.