kern/51318: Renice idle process not illegal; causes hang

Craig Reyenga creyenga at connectmail.carleton.ca
Wed Apr 23 10:00:31 PDT 2003


>Number:         51318
>Category:       kern
>Synopsis:       Renice idle process not illegal; causes hang
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Apr 23 10:00:16 PDT 2003
>Closed-Date:
>Last-Modified:
>Originator:     Craig M. R.
>Release:        FreeBSD 5.0-CURRENT i386
>Organization:
My Room
>Environment:
System: FreeBSD cesspool 5.0-CURRENT FreeBSD 5.0-CURRENT #1: Sat Apr 12
18:47:02 EDT 2003
                craig at cesspool:/usr/obj/usr/src/sys/CKERN i386


        <machine, os, target, libraries (multiple lines)>
>Description:
        I tried 'renice -n -20 10' (pid 10 is idle thread) to see what would
        happen. Turns out that this operation isn't illegal, the system hung
        accordingly, and the console started displaying this message:

        swap_pager: indefinite wait buffer: device: ad0s1b, blkno: 776,
size: 4096

        over and over, although not rapidly.

        Using SCHED_ULE 1.27

>How-To-Repeat:
        'renice -n -20 10'
>Fix:

        setpriority() should return [EINVAL] for pid 10, or the process
        should have some flag set to disallow reniceing the idle process.



>Release-Note:
>Audit-Trail:
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