Re: Signal handling possibly wrong

[Bodo Stroesser <bstroesser@fujitsu-siemens.com>]

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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