libc_r silliness

[David Xu]

----- Original Message ----- 
From: "Daniel Eischen" <eischen at vigrid.com>
To: "John Baldwin" <jhb at FreeBSD.org>
Cc: "David Xu" <davidxu at viatech.com.cn>; <threads at FreeBSD.org>
Sent: Wednesday, July 09, 2003 8:12 AM
Subject: Re: libc_r silliness


> On Tue, 8 Jul 2003, John Baldwin wrote:
> > On 08-Jul-2003 Daniel Eischen wrote:
> > > On Tue, 8 Jul 2003, John Baldwin wrote:
> > >> So is X/Open OSI whoever just assuming that the process and thread
> > >> scheduling policies implement identical priority ranges?
> > > 
> > > I dunno, but it seems that is the case.
> > > 
> > > We could add pthread_get_priority_{min,max}_np(int policy) as
> > > non-portable functions.
> > 
> > We could also just force all the thread libraries and kernel to
> > use the same priority ranges.
> 
> I don't want to have SCHED_OTHER with -20 .. 20 in libpthread.
> 
> > Another possibility is to have
> > each thread library provide their own sched_get_{min,max} and
> > wrap the sched_{get,set}schedparam() syscalls to massage the
> > thread priority values into their corresponding process priority
> > values to simulate a single priority space for each policy.
> 
> I like this better than the other option, but how do you
> know that when the application calls sched_setschedparam()
> with a priority of 10, that it really came from
> sched_get_priority_min() + 10 (meaning -10) or whether it was
> hardcoded to 10 and really wants 10.
> 

>From a book "Programming for the real world POSIX.4",
The author said about sched_get_priority_max/min:
   Notes:
        Since the range of scheduling priorities varies from system
        to system, applications should refrain from calling the POSIX.4
        scheduling algorithms with straight priority numbers. Rather,
        a virtual priority range should be used; then it should be shifted
        appropriately based on the values returned from sched_get_priority_min
        and sched_get_priority_max.

> -- 
> Dan Eischen
> 
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