2009-03-11 07:59:16 Problem with Shared Memory IPC

der knut (GERMANY)

Message: 70770

Hello,

as described at

https://blackfin.uclinux.org/gf/project/uclinux-dist/forum/?action=ForumBrowse&forum_id=39&_forum_action=ForumMessageBrowse&thread_id=32758

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

.......

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

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