[Bug nptl/13165] pthread_cond_wait() can consume a signal that was sent before it started waiting

["mihaylov.mihail at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13165

--- Comment #21 from Mihail Mihaylov <mihaylov.mihail at gmail dot com> 2012-09-20 11:05:21 UTC ---
(In reply to comment #20)
> The standard indeed doesn't talk about the "future".  It doesn't make a sort of
> lower-bound requirement on which threads have to be considered blocked, but no
> upper bound.  If you think there's an upper bound, please point the requirement
> in the standard.  If there is no required upper bound, it's up to the
> implementation how to deal with that.

"The pthread_cond_broadcast() and pthread_cond_signal() functions shall have no
effect if there are no threads currently blocked on cond."

How about this as an upper bound? If implementations are allowed to determine
the set of blocked threads at any point in time they see fit, there would be no
way to define "currently blocked" at all and this sentence couldn't make any
sense.

And also:

".... however, if predictable scheduling behavior is required, then that mutex
shall be locked by the thread calling pthread_cond_broadcast() or
pthread_cond_signal()."

If I accept your argument, there will be no way to determine at least a set of
threads from which the woken thread will be chosen, so why does the standard
talk about predictability?

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.