system priorities

[Daniel Eischen]

On Sat, 1 May 2004, Petri Helenius wrote:

> Daniel Eischen wrote:
> 
> >
> >It looks like rtprio will set the priority of the first
> >KSEG in the proc's list of KSEGs.  This isn't necessarily
> >the first KSEG created (main).  In fact, newly created
> >KSEGs get inserted onto the head of the list, so rtprio()
> >may act on different KSEGs depending on if it is called
> >before or after any KSEG creations.
> >
> >  
> >
> This sounds like a bug. Could it change the KSEG which called the rtprio 
> so there would be some deterministic behaviour to the rtprio if used in 
> threaded program? So I take it from this that rtprio is also broken for 
> libthr?

Yes.

> >I would really like a Solaris-like priocntl() so that you
> >can specify which KSEG (or whatever thing that will hold
> >the priority in the future) to act on.
> >
> >  
> >
> I fail to understand the value of being able to point to other threads 
> for priority setting? Or are you talking about a facility which would 
> exist below the rtprio call?

The Solaris priocntl() lets you set/get:

     P_LWPID
           The id argument is an LWP ID.  The  priocntl  function
           applies  to  the  LWP with the specified ID within the
           calling process.

     P_PID The id argument is a process ID  specifying  a  single
           process.  The  priocntl() function applies to all LWPs
           currently associated with the specified process.

     P_PPID
           The id argument is a parent process ID. The priocntl()
           function applies to all LWPs currently associated with
           processes with the specified parent process ID.

     P_PGID
           The id argument is a process group ID. The  priocntl()
           function applies to all LWPs currently associated with
           processes in the specified process group.

     P_SID The id argument is a session ID. The priocntl()  func-
           tion  applies  to  all  LWPs currently associated with
           processes in the specified session.

     P_TASKID
           The id argument is a task ID. The priocntl()  function
           applies   to   all   LWPs  currently  associated  with
           processes in the specified task.

     P_CID The id  argument  is  a  class  ID  (returned  by  the
           priocntl()  PC_GETCID command as explained below). The
           priocntl() function applies to all LWPs in the  speci-
           fied class.

     P_UID The id argument is a user ID. The priocntl()  function
           applies to all LWPs with this effective user ID.

     P_GID The id argument is a group ID. The priocntl() function
           applies to all LWPs with this effective group ID.

     P_PROJID
           The id argument is a project ID. The priocntl()  func-
           tion applies to all LWPs with this project ID.

     P_ALL The priocntl() function applies to all existing  LWPs.
           The  value  of  id is ignored. The permission restric-
           tions described below still apply.

     P_MYID
           The calling LWP's LWP_ID, PPID, GID, SID, TASKID, CID,
           UID, GID, or PROJID...

We probably don't need all these, but perhaps some of them could
be useful.

-- 
Dan Eischen