Re: Signal handling possibly wrong

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

> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > Where, sa_mask is _ignored_ if NODEFER is set. (I now have woken up!).
> > The attached program shows that the sa_mask is indeed ignored when
> > SA_NODEFER is set.
> > 
> > Now the real question is... Is this a bug?
> 
> That's not correct w.r.t. SUSv3.  sa_mask should be always used and
> SA_NODEFER is just whether or not to add that signal in.

Yes.

> SA_NODEFER
>     [XSI] If set and sig is caught, sig shall not be added to the 
>     thread's
>     signal mask on entry to the signal handler unless it is included in
>     sa_mask. Otherwise, sig shall always be added to the thread's signal
>     mask on entry to the signal handler.

It's amazing that this non-conformance was never spotted before.
It seems to go all the way back to kernel 1.0 (when the flag
was known as SA_NOMASK).

I'll get something into the manual pages under BUGS.

Cheers,

Michael

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

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