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Message-Id: <201106061143.p56Bhdbk021809@red.freebsd.org>
Date: Mon, 6 Jun 2011 11:43:39 GMT
From: "Dmitry V. Krivenok" <krivenok.dmitry@gmail.com>
To: freebsd-gnats-submit@FreeBSD.org
Subject: ksched_setscheduler interprets TS priority as RT priority
X-Send-Pr-Version: www-3.1
X-GNATS-Notify:

>Number:         157657
>Category:       kern
>Synopsis:       [kernel] [patch] ksched_setscheduler interprets TS priority as RT priority
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jun 06 11:50:12 UTC 2011
>Closed-Date:    Thu Jun 23 06:35:29 UTC 2011
>Last-Modified:  Thu Jun 23 06:35:29 UTC 2011
>Originator:     Dmitry V. Krivenok
>Release:        CURRENT
>Organization:
>Environment:
FreeBSD csx-spb-freebsd9.sspg.lab.emc.com 9.0-CURRENT FreeBSD 9.0-CURRENT #0 r222722M: Mon Jun  6 14:31:25 MSD 2011     root@csx-spb-freebsd9.sspg.lab.emc.com:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
At line 209 of ksched_setscheduler function TS priority is interpreted as RT priority:

205                 case SCHED_OTHER:
206                 if (param->sched_priority >= 0 &&
207                         param->sched_priority <=
(PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE)) {
208                         rtp.type = RTP_PRIO_NORMAL;
209                         rtp.prio = p4prio_to_rtpprio(param->sched_priority);
210                         rtp_to_pri(&rtp, td);
211                 } else
212                         e = EINVAL;

I think that p4prio_to_tsprio should be used instead of p4prio_to_rtpprio.
>How-To-Repeat:
Compile the following program:
gcc -Wall setscheduler_bug.c -o setscheduler_bug

#include <assert.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/param.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char** argv)
{
  int r;
  struct sched_param param;
  assert(argc == 2);
  r = sched_getscheduler(getpid());
  assert(r != -1);
  printf("Initial policy: %d\n", r);
  r = sched_getparam(getpid(), &param);
  assert(r != -1);
  printf("Initial priority: %d\n", param.sched_priority);

  param.sched_priority = atoi(argv[1]);
  r = sched_setscheduler(getpid(), SCHED_OTHER, &param);
  assert(r != -1);

  r = sched_getparam(getpid(), &param);
  assert(r != -1);
  printf("New priority: %d\n", param.sched_priority);

  return 0;
}

and run it with root permissions:

$ sudo ./setscheduler_bug 32
Initial policy: 2
Initial priority: 100
New priority: 100
$ sudo ./setscheduler_bug 0
Initial policy: 2
Initial priority: 100
New priority: 72
$

As you can see new priorities are wrong.
>Fix:
Apply the following patch and rebuild the kernel

Index: sys/kern/ksched.c
===================================================================
--- sys/kern/ksched.c   (revision 222722)
+++ sys/kern/ksched.c   (working copy)
@@ -206,7 +206,7 @@
                if (param->sched_priority >= 0 &&
                        param->sched_priority <= (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE)) {
                        rtp.type = RTP_PRIO_NORMAL;
-                       rtp.prio = p4prio_to_rtpprio(param->sched_priority);
+                       rtp.prio = p4prio_to_tsprio(param->sched_priority);
                        rtp_to_pri(&rtp, td);
                } else
                        e = EINVAL;


Then run the same program again and you should see expected priorities:

$ sudo ./setscheduler_bug 32
Initial policy: 2
Initial priority: 100
New priority: 32
$ sudo ./setscheduler_bug 0
Initial policy: 2
Initial priority: 100
New priority: 0
$

>Release-Note:
>Audit-Trail:

From: dfilter@FreeBSD.ORG (dfilter service)
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/157657: commit references a PR
Date: Tue,  7 Jun 2011 02:50:24 +0000 (UTC)

 Author: davidxu
 Date: Tue Jun  7 02:50:14 2011
 New Revision: 222802
 URL: http://svn.freebsd.org/changeset/base/222802
 
 Log:
   Use p4prio_to_tsprio to calculate TS priority instead of using
   p4prio_to_rtpprio which is for RT priority.
   
   PR:	kern/157657
   Submitted by:	krivenok.dmitry at gmail dot com
   MFC after:	3 days
 
 Modified:
   head/sys/kern/ksched.c
 
 Modified: head/sys/kern/ksched.c
 ==============================================================================
 --- head/sys/kern/ksched.c	Tue Jun  7 01:28:12 2011	(r222801)
 +++ head/sys/kern/ksched.c	Tue Jun  7 02:50:14 2011	(r222802)
 @@ -206,7 +206,7 @@ ksched_setscheduler(struct ksched *ksche
  		if (param->sched_priority >= 0 &&
  			param->sched_priority <= (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE)) {
  			rtp.type = RTP_PRIO_NORMAL;
 -			rtp.prio = p4prio_to_rtpprio(param->sched_priority);
 +			rtp.prio = p4prio_to_tsprio(param->sched_priority);
  			rtp_to_pri(&rtp, td);
  		} else
  			e = EINVAL;
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State-Changed-From-To: open->closed 
State-Changed-By: davidxu 
State-Changed-When: Thu Jun 23 06:34:39 UTC 2011 
State-Changed-Why:  
Fixed. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=157657 
>Unformatted:
