# PREEMPTION on causing system to pause



## jcarlson (Feb 22, 2010)

I'm running 7.1 on an IXP425 embedded SBC (Avila). The SBC is used to host a pt2pt Wifi bridge. I have been experiencing periodic packet errors (10-6) where I believe the qmgr0 and the ath0 intr are colliding (occasional mbuf exhaustion). I recently turned on PREEMPTION and all errors cease but after several minutes the system stops passing packets and when I enter anything on the serial port, it resumes, thus I can't see what had happened. I am a bit disparate here and will reward a solution provider handsomely. I am also wondering how to ensure the interrupts are prioritized appropriately and if remote debugging would be of use.. 

```
top -S
  PID USERNAME  THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
   10 root        1 171 ki31     0K  1952K RUN     21:14 87.21% idle
   20 root        1 -68    -     0K  1952K WAIT     1:22  5.13% intr3: ixpqmgr0
   18 root        1 -68    -     0K  1952K WAIT     0:51  2.93% intr27: ath0
    7 root        1 -68    -     0K  1952K -        1:01  1.03% ath0 taskq
  733 root        1   8    0  4076K  1112K nanslp   0:07  0.00% sentry
   24 root        1 -64    -     0K  1952K WAIT     0:04  0.00% intr29: ata_avi
   11 root        1 -32    -     0K  1952K WAIT     0:04  0.00% swi4: clock
  723 root        1   8    0  3692K   984K nanslp   0:01  0.00% dials
  728 root        1  96    0  4080K  1700K mqrecv   0:01  0.00% kahuna
    4 root        1  -8    -     0K  1952K -        0:01  0.00% g_down
    3 root        1  -8    -     0K  1952K -        0:00  0.00% g_up
    2 root        1  -8    -     0K  1952K -        0:00  0.00% g_event
   14 root        1 -16    -     0K  1952K -        0:00  0.00% yarrow
  946 root        1  96    0  5048K  2480K select   0:00  0.00% mini_httpd
   45 root        1  -8    -     0K  1952K mdwait   0:00  0.00% md0
   29 root        1 -16    -     0K  1952K -        0:00  0.00% schedcpu
 1063 root        1  20    0  3768K  2144K pause    0:00  0.00% csh
```
 Jim Carlson 707 223 4000


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## jcarlson (Mar 4, 2010)

*update from Preemption issue*

turns our deadlocking was occurring - WITNESS helped -
 I still haven't found a way to manually adjust the priority of interrupts successfully. renice, doesn't do interrupts nor does rtprio. Maybe someone can help me with that.


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