Re: Signal handling possibly wrong

[Robert Wilkens <robw@optonline.net>]

[resent - previous message not properly addressed]

It says "signal is blocked, UNLESS SA_NODEFER is used.."

Which means if NODEFER is used, it's not masked (SA_NOMASK)..

I don't understand how i'm wrong (maybe I have mental problems that are
worse than I thought).  If you want to explain off-list or on-list
(depending on whether others are getting annoyed at me) you can.  Or
just ignore me and i'll go away and someone else who wants to look at it
can.

-Rob
On Tue, 2005-08-09 at 20:44 +0200, Bodo Stroesser wrote:
> Robert Wilkens wrote:
> > Bodo,
> > 
> > SA_MASK is a flag... Which you use to tell it what to do with the data
> > you've given it and/or it gets.  You gave it sa_mask (lower-case).
> > SA_NOMASK means don't use the mask -- the pseudonym (new-word) for
> > SA_NOMASK is SA_NODEFER (renamed, perhaps, because it may defer some or
> > all signals rather than throwing them away, you probably can receive the
> > waiting signals by clearing the SA_NODEFER flag on a subsequent call).
> > 
> > If you want to take this off-list, I'm OK with that..
> > 
> > Please describe what you would expect SA_NODEFER to do in your own
> > language if you don't understand what I seem to understand.
> > 
> > -Rob
> > On Tue, 2005-08-09 at 20:32 +0200, Bodo Stroesser wrote:
> > 
> 
> Sorry, unfortunately you are not right. See this (from man page for sigaction):
> 
> struct sigaction {
>                    void (*sa_handler)(int);
>                    void (*sa_sigaction)(int, siginfo_t *, void *);
>                    sigset_t sa_mask;
>                    int sa_flags;
>                    void (*sa_restorer)(void);
>                }
> 
> Please read the text about element sa_mask of struct sigaction to
> understand what I'm talking about.
> 
> Regards
> 	Bodo
> 
> 
> >>Robert Wilkens wrote:
> >>
> >>>>Kernel code blocks both "handled signal" _and_ sa_mask only if SA_NODEFER
> >>>>isn't set.
> >>>>
> >>>>Which is the right behavior?
> >>>
> >>>
> >>>Perhaps both?
> >>>
> >>>I'm novice here, but if i'm reading the man page correctly, it says:
> >>>
> >>>SA_NODEFER
> >>>   Do not prevent the signal from being received from within
> >>>   its  own  signal handler. 
> >>>	(they also imply that SA_NOMASK is the old name for this,
> >>>	which might make it clear what it's use is).
> >>>
> >>>In which case blocking (masking) when it's not set is exactly what it's
> >>>supposed to do.
> >>>
> >>>-Rob
> >>
> >>Yes. That's true.
> >>
> >>But what about sa_mask? Description of SA_NODEFER and sa_mask both do not
> >>say, that usage of sa_mask depends on SA_NODEFER.
> >>But kernel only uses sa_mask, if SA_NODEFER isn't set.
> >>
> >>So, I think man page and kernel are not consistent.
> >>
> >>	Bodo
> >>-
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