Re: [PATCH] posix timers using == instead of & for bitmask tests

[Joe Korty <joe.korty@ccur.com>]

On Fri, Oct 22, 2004 at 03:03:20PM -0700, Roland McGrath wrote:
> > Make posix-timers do a get_task_struct / put_task_struct if either
> > SIGEV_SIGNAL or SIGEV_THREAD_ID is set.  Currently the get/put is done
> > only if both are set.
> 
> What is the purpose of this change?  The `good_sigevent' check ensures that
> if SIGEV_THREAD_ID is set, then the value is exactly
> SIGEV_SIGNAL|SIGEV_THREAD_ID.  In fact, this change has no effect at all
> because SIGEV_SIGNAL is zero.  If it weren't, it would have an undesireable
> effect of doing the task_struct refcounting all the time instead of only
> for SIGEV_THREAD_ID.  That refcounting is never required in the plain
> SIGEV_SIGNAL case, because the task_struct pointer stored in the
> group_leader, and that is never freed before all the posix-timers data
> structures get cleared out anyway (exit_itimers).  It's only required for
> SIGEV_THREAD_ID, where the target thread might have died before the timer
> was next examined.

Hi Roland,
 Thanks for answering my mistaken impressions.  I saw after I wrote that
SIGEV_SIGNAL == 0 which makes everything work.  And I was laboring under
the misconception that SIGEV_SIGNAL and SIGEV_THREAD were mutually exclusive
which isn't true, one always has SIGEV_SIGNAL if SIGEV_THREAD is set.

Regards,
Joe