[LTP] question about signal handling in tst_sig()

[LTP] question about signal handling in tst_sig()

[Han Pingtian]

Hi there,

Looks like in tst_sig(), if _SC_SIGRT_MIN defined, all realtime signals
won't be set an handler:

125 #ifdef _SC_SIGRT_MIN
126                 if (sig >= sigrtmin && sig <= sigrtmax)
127                         continue;
128 #endif

but, if it wasn't defined, then all realtime signals will be set an
handler:

134 #if !defined(_SC_SIGRT_MIN) && defined(__SIGRTMIN) &&
defined(__SIGRTMAX)
135                         /* Ignore all real-time signals */
136                 case __SIGRTMIN:
137                 case __SIGRTMIN + 1:
...

is that correct, or I missed something here? 

Thanks in advance!

[LTP] question about signal handling in tst_sig()

[Cyril Hrubis]

Hi!
> Looks like in tst_sig(), if _SC_SIGRT_MIN defined, all realtime signals
> won't be set an handler:
> 
> 125 #ifdef _SC_SIGRT_MIN
> 126                 if (sig >= sigrtmin && sig <= sigrtmax)
> 127                         continue;
> 128 #endif
> 
> but, if it wasn't defined, then all realtime signals will be set an
> handler:
> 
> 134 #if !defined(_SC_SIGRT_MIN) && defined(__SIGRTMIN) &&
> defined(__SIGRTMAX)
> 135                         /* Ignore all real-time signals */
> 136                 case __SIGRTMIN:
> 137                 case __SIGRTMIN + 1:
> ...
> 
> is that correct, or I missed something here? 

The loop goes over signal numbers from 1 to NSIG (which is defined in
system headers). Supposedly when _SC_SIGRT_MIN is not defined the system
does not support realtime signals and the NSIG has value of the highest
allocated (non-realtime) signal number.

-- 
Cyril Hrubis
chrubis@suse.cz

[LTP] question about signal handling in tst_sig()

[Cyril Hrubis]

Hi!
> > Looks like in tst_sig(), if _SC_SIGRT_MIN defined, all realtime signals
> > won't be set an handler:
> > 
> > 125 #ifdef _SC_SIGRT_MIN
> > 126                 if (sig >= sigrtmin && sig <= sigrtmax)
> > 127                         continue;
> > 128 #endif
> > 
> > but, if it wasn't defined, then all realtime signals will be set an
> > handler:
> > 
> > 134 #if !defined(_SC_SIGRT_MIN) && defined(__SIGRTMIN) &&
> > defined(__SIGRTMAX)
> > 135                         /* Ignore all real-time signals */
> > 136                 case __SIGRTMIN:
> > 137                 case __SIGRTMIN + 1:
> > ...

And also there is a break down after the long list of cases.


So it looks like:

* if _SC_SIGRT_MIN is defined we have a POSIX compilant system
  and we skip realtime signals in the if at line 125.

* Otherwise if system is not POSIX compilant but __SIGRTMIN and
  __SIGRTMAX is defined, we skip them in the hack in the switch()

  this is possibly workaround for old glibc without _SC_SIGRT_MIN
  support

> > is that correct, or I missed something here? 
> 
> The loop goes over signal numbers from 1 to NSIG (which is defined in
> system headers). Supposedly when _SC_SIGRT_MIN is not defined the system
> does not support realtime signals and the NSIG has value of the highest
> allocated (non-realtime) signal number.
> 
> -- 
> Cyril Hrubis
> chrubis@suse.cz
> 
> -- 
> Mailing list info: http://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz

[LTP] question about signal handling in tst_sig()

[Han Pingtian]

On Mon, Mar 14, 2016 at 02:43:21PM +0100, Cyril Hrubis wrote:
> Hi!
> > > Looks like in tst_sig(), if _SC_SIGRT_MIN defined, all realtime signals
> > > won't be set an handler:
> > > 
> > > 125 #ifdef _SC_SIGRT_MIN
> > > 126                 if (sig >= sigrtmin && sig <= sigrtmax)
> > > 127                         continue;
> > > 128 #endif
> > > 
> > > but, if it wasn't defined, then all realtime signals will be set an
> > > handler:
> > > 
> > > 134 #if !defined(_SC_SIGRT_MIN) && defined(__SIGRTMIN) &&
> > > defined(__SIGRTMAX)
> > > 135                         /* Ignore all real-time signals */
> > > 136                 case __SIGRTMIN:
> > > 137                 case __SIGRTMIN + 1:
> > > ...
> 
> And also there is a break down after the long list of cases.
> 
> 
> So it looks like:
> 
> * if _SC_SIGRT_MIN is defined we have a POSIX compilant system
>   and we skip realtime signals in the if at line 125.
> 
> * Otherwise if system is not POSIX compilant but __SIGRTMIN and
>   __SIGRTMAX is defined, we skip them in the hack in the switch()
> 
Thanks so much, I just noticed that there is a "break;" at line 206 ...