2009-02-27 07:46:44     Problem with Shared Memory / MPU

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2009-02-27 07:46:44     Problem with Shared Memory / MPU

der knut (GERMANY)

Message: 70094   

 

Hello,

 

we use shared memory to pass information from our main app. to the webserver for display it to the user. With shmget/shmat/.. it works fine with ARM/MMU.

 

If I try to port this to BF526 / uClinux / SVN trunk / bfin-linux-uclibc I get strange behavior:

 

1) Both, app. and webserver, work fine single started but can not run together

 

2) If I activate MPU, none of the app. run, get exception on first read/write from/to shared memory. Return values and adresses looks good if I call shmget / shmat, the memory adress ist a valid dyn. memory.

 

Data access CPLB protection violation

- Attempted read or write to Supervisor resource,

   or illegal data memory access.

Kernel process context

CURRENT PROCESS:

COMM=ets PID=482

TEXT = 0x01000000-0x0131b9b8        DATA = 0x015009b8-0x015e32ac

BSS = 0x015e32ac-0x01440000  USER-STACK = 0x0145fee0

 

return address: [0x0118d17e]; contents of:

0x0118d150:  801a  5008  3210  9110  e801  0000  0010  0000

0x0118d160:  e800  0002  bbeb  b9ea  e410  2424  3210  9110

0x0118d170:  0c00  1836  b9ea  e410  2424  3210  9152 [9950]

0x0118d180:  4300  e121  004c  0808  1028  b9ea  e410  2424

 

SEQUENCER STATUS:               Tainted: P

SEQSTAT: 00060023  IPEND: 0030  SYSCFG: 0006

  EXCAUSE   : 0x23

RETE: <0x00000000> { _run_init_process + 0xfffff000 }

RETN: <0x006f2000> /* kernel dynamic memory */

RETX: <0x00000480> /* Maybe fixed code section */

RETS: <0x0118d676> [ /opt/auerswald/ets + 0x18d676 ]

PC  : <0x0118d17e> [ /opt/auerswald/ets + 0x18d17e ]                // first read access to shm <0x01434000>

DCPLB_FAULT_ADDR: <0x01434000> [ /SYSV000009d0 (deleted) + 0x0 ]     // shm adress returned by shmat()

ICPLB_FAULT_ADDR: <0x0000ffff> { _register_console + 0x8f }

 

...........................

 

What I am doing wrong?

 

Thanks a lot

 

Knut

 

 

 

 

shm_app.txt

shm_webserver.txt

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2009-02-27 10:16:02     Re: Problem with Shared Memory / MPU

Phil Wilshire (UNITED STATES)

Message: 70101   

 

Knut,

 

Can you reproduce this error with a small code sample ( not the full app ) that you can post here.

 

 

 

Regards

 

  Phil Wilshire

 

 

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2009-03-02 04:48:06     Re: Problem with Shared Memory / MPU

der knut (GERMANY)

Message: 70206   

 

Hello Phil,

 

thank you for fast response. I wrote a little test on weekend, but I am only now in office again to test on hardware (BF526 Rev.0.0 / BF527 Rev 0.2). My BF537 Rev 0.2 STAMP board at home is to old and can not use MPU due an anomaly.

 

Attached little test "intest" init shared memory (shm) and write input to shm. "outtest" print first 10 characters from shm every second. Both exit if first charachter is 'X'. This works without MPU and cause a "Data access CPLB protection violation -  attempted read or write to Supervisor resource, or illegal data memory access." if MPU is switched on at kernel config.

 

Thanks a lot for help

 

Knut

 

shmdemo.tgz

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2009-03-02 04:54:29     Re: Problem with Shared Memory / MPU

der knut (GERMANY)

Message: 70208   

 

Ooops,

 

please ignore the double line

 

    shm_id = shmget(1234, TEST_LEN, IPC_CREAT | 0666);

 

 

its a copy/paste artefact, but does not cause the problem.

 

Thanks a lot

 

Knut

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2009-03-02 11:37:08     Re: Problem with Shared Memory / MPU

Mike Frysinger (UNITED STATES)

Message: 70227   

 

i'm guessing this works properly with the MPU turned off ?

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2009-03-03 01:39:12     Re: Problem with Shared Memory / MPU

der knut (GERMANY)

Message: 70246   

 

Hello,

 

yes, no problem without MPU. But I am looking for another problem and hope MPU will help if it is working.

 

Thanks

 

Knut

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2009-03-03 02:08:36     Re: Problem with Shared Memory / MPU

Mike Frysinger (UNITED STATES)

Message: 70250   

 

ive opened a tracker item so the issue can be looked at in more detail:

blackfin.uclinux.org/gf/tracker/4948

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2009-03-20 18:09:55     Re: Problem with Shared Memory / MPU

Mike Frysinger (UNITED STATES)

Message: 71321   

 

can you update latest svn trunk and see if it works now ?

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