Re: [PATCH 6/7] Block all signals on timer_create thread (BZ#10815)

[Florian Weimer <fweimer at redhat dot com>]

* Adhemerval Zanella:

>> I think this does not unblock SIGCANCEL on the new thread with the
>> current pthread_create implementation.  This will change with the
>> block-signals-around-clone patch I submitted, though.
>
> It does not indeed, although not sure how valid is the scenario to
> pthread cancel a thread not created explicitly by a pthread_create
> issued by the user (since POSIX also state it is not valid to call
> pthread_join() timer thread).

I don't see any restrictions on calling pthread_cancel or pthread_exit.

> The sigcancel is explicit blocked with __libc_signal_block_sigtimer
> on __start_helper_thread, so sigwaitinfo would be the only point
> where the timer is triggered.  I don't think it is correct to unblock
> it before calling pthread_create, so the created thread inherit the
> unblock SIGCANCEL, for the same reason the SIGCANCEL is blocked on the
> helper thread that calls sigwaitinfo (possible lose wakeups).

We can wrap the thread start function with another function that
unblocks SIGCANCEL.  Or note the semantic difference on the other change
(which I assume we still want for other reasons).

Thanks,
Florian