Bug#503162: libc6: Doubt with nptl

[Petr Salinger <Petr.Salinger@seznam.cz>]

> Thank you very much for answering me. And if you don't mind I'll ask one
> more question. In the open group manual there is this line "Implementations
> are allowed
> to favour writers over readers to avoid writer starvation."
> And linux manual says: "If the Thread Execution Scheduling option is
> supported, and the
> threads involved in the lock are executing with the scheduling policies
> SCHED_FIFO or
> SCHED_RR, the calling thread shall not acquire the lock if a writer holds
> the lock or
> if writers of higher or equal priority are blocked on the lock; otherwise,
> the calling thread
> shall acquire the lock."
> The sysconf call showed that "_SC_THREAD_PRIORITY_SCHEDULING" option is
> enabled in my system.
> But adding "pthread_attr_setschedpolicy(&pthread_attr, SCHED_FIFO)" line
> before the
> "pthread_create" call didn't affect anything. What's wrong now?

I do not know. May be scheduling of whole process have to be set,
may be it have to have enough priviledge to set SCHED_FIFO.
Or the manual does not reflect glibc reality.

But even in the original case, the writers are really favored over 
readers. When the write-lock is released, it is acquired by another 
writer, even iff the writer asked for a lock after reader.

Petr