Shared memory shmat/dt not working well in 2.5.x

From: Zlatko Calusic (zlatko.calusic@iskon.hr)
Date: Tue Oct 01 2002 - 04:52:59 EST

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Hi, Andrew, Hugh & others.

Still having problems with Oracle on 2.5.x (it can't even be started),
I devoted some time trying to pinpoint where the problem is. Reading
many traces of Oracle, and rebooting a dozen times, I finally found
that the culprit is weird behaviour of shmat/shmdt functions in 2.5,
when combined with mprotect() calls. I wrote a simple test app
(attached) and I'm also appending output of it below (running on
2.4.19 & 2.5.39 kernels, see the difference).

Hopefully, somebody will know how to help resolve that issue, so I can
finally benchmark Oracle on 2.4 vs Oracle on 2.5. ;)

Best regards,

{2.4.19} % shm-bug
First shmat & protects done: 50000000
50000000-51000000 rw-s 00000000 00:04 327974932 /SYSV01478e7f (deleted)
51000000-51001000 r--s 01000000 00:04 327974932 /SYSV01478e7f (deleted)
51001000-51081000 rw-s 01001000 00:04 327974932 /SYSV01478e7f (deleted)
51081000-51082000 r--s 01081000 00:04 327974932 /SYSV01478e7f (deleted)
51082000-51083000 rw-s 01082000 00:04 327974932 /SYSV01478e7f (deleted)
Second shmat done: 50000000
50000000-51083000 rw-s 00000000 00:04 327974932 /SYSV01478e7f (deleted)

{2.5.39} % shm-bug
First shmat & protects done: 50000000
50000000-51000000 rw-s 00000000 00:06 2457614 /SYSV01478e7f (deleted)
51000000-51001000 r--s 00000000 00:06 2457614 /SYSV01478e7f (deleted)
51001000-51081000 rw-s 00001000 00:06 2457614 /SYSV01478e7f (deleted)
51081000-51082000 r--s 00001000 00:06 2457614 /SYSV01478e7f (deleted)
51082000-51083000 rw-s 00002000 00:06 2457614 /SYSV01478e7f (deleted)
shmat 2: Invalid argument

text/x-csrc attachment: shm-bug.c

-- Zlatko

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