Re: The problem with __pthread_manager_adjust_prio

[Ulrich Drepper <drepper at redhat dot com>]

On Mon, 2002-04-15 at 13:35, H . J . Lu wrote:

> 1. pthread_start_thread needs to know the manager's priority when clone
> is called. There is no way to tell what the value will be since it can
> be changed at any time by __pthread_manager_adjust_prio. One way to
> solve it is not to check manager->p_priority in pthread_start_thread
> at all and always set SCHED_OTHER by default.
> 2. There is a race conditon between __pthread_manager_adjust_prio
> since diffetent threads can call it at any time.

There are many different ways to handle this and yes, thread-local
variables are needed.

In adjust_prio you set a flag before calling the syscall.  After the
syscall you update the p_priority element and then you clear the flag.

When starting a new thread and the flag is not set communicate the new
priority in a thread-local variable to the new thread.  If the flag is
set communicate this information and have the new thread unconditionally
set the scheduler and priority.

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