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

[Roland McGrath]

> 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.


Thanks,
Roland

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