signalfd and thread semantics

[Michael Kerrisk <mtk-manpages@gmx.net>]

Hi Davide,

Working on the signalfd man page, another question comes up:

What are the intended semantics for a signalfd file descriptor with respect
to threads?  I have not yet tested the behavior, but in any case, I better
check what is expected.

A signal can be directed to the process as a whole (e.g., using kill(2)),
or to a particular thread (using, e.g., pthread_kill(2), or tgkill(2)).

So that raises the question: If a thread calls signalfd(), does the
resulting file descriptor return just those signals directed to [the thread
and the process as a whole], or will it also receive signals that are
targeted at other threads in the process?  I would hope the former is the
case, but I'm not sure what has been implemented (or intended).

Cheers,

Michael

-- 
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7

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