2009-03-11 07:59:16 Problem with Shared Memory IPC
der knut (GERMANY)
Message: 70770
Hello,
as described at
and tracker item #4948 I am looking for a problem with shared memory.
It seem that the shared memory was reused by kernel or something else.
1) Latest Kernel SVN revision 6167; MPU disabled
2) Toolchain SVN snapshot Feb. 2009
3) Start linux on BF526 Rev 0.0 custom board with root mounted with nfs (every fs action == ethernet action)
4) Test app. from bug tracker item #4948 (shmtest.c)
5) Start "shmtest r" at console
6) Start "shmtest w" at first telnet session and type "testtesttest"
7) On console / "shmtest r" outout is
testtestte
testtestte
testtestte
testtestte
.......
as expected.
8) I do some memory operations, like
echo 3 > /proc/sys/vm/drop_caches
copy some files
echo 3 > /proc/sys/vm/drop_caches
for several times on a second telnet session.
9) Output of "shmtest r" change
.....
testtestte
testtestte
testtestte
testtestte
testtestte
testtestte
testtestte
testtestte
H�
H�
H�
H�
H�
H�
H�
H�
........
It look like something wrote on shared memory while "shmtest" own this memory.
If I type something else to "shmtest w" everything is looking fine again as long as I use some cache and free it like described above. After a while running the system the error disappear, it seems that shared memory is in stable use by something other and not any longer used by cache (?).
This also happend if we start our applications, I reduce the problem like described above to exclude our code.
What I am doing wrong?
Thanks a lot
Knut
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2009-03-11 22:31:34 Re: Problem with Shared Memory IPC
Mike Frysinger (UNITED STATES)
Message: 70805
can you try this patch and see if it fixes things ?
thread.gmane.org/gmane.linux.hardware.blackfin.kernel.devel/1275
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2009-03-12 15:44:00 Re: Problem with Shared Memory IPC
der knut (GERMANY)
Message: 70884
Hello,
thanks a lot for fast and excellent help.
Now it works.
Thanks
Knut