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blockio tapset problem

Hi -

While running the unified dejagnu bucket (which I'm about to commit
btw), I ran into one failure associated with the recent ioblock
tapset.  In particular, this kernel panic occurred (just once) on a
busy vmware box running the RHEL4U4 kernel:

EIP:    0060:[<d5b24433>]    Tainted: P      VLI
EFLAGS: 00010082   (2.6.9-42.EL)
EIP is at function___bio_ino+0x3e/0x4c [stap_13844]
eax: 001d244b   ebx: 00000000   ecx: 00000000   edx: c18fa2c4
esi: c18fa000   edi: c18fa01c   ebp: d48e0d88   esp: d48e0cec
ds: 007b   es: 007b   ss: 0068
Process kswapd0 (pid: 38, threadinfo=d48e0000 task=d48ce0b0)
Stack: d5b248c5 c18fa000 d5b26494 00000046 d5b24d71 d5b68720 d48e0d88 c025870c
       c0405f20 c011bf04 00000000 c036b7e0 d48e0d88 00000002 00000001 c011c1cd
       00000000 c036b7e0 d48e0d54 00000002 00000001 c01348a1 d48e0d88 00000000
Call Trace:
 [<d5b248c5>] probe_805+0x1d4/0x5ff [stap_13844]
 [<d5b24d71>] enter_probe_805+0x35/0x45 [stap_13844]
 [<c025870c>] generic_make_request+0x2/0x1a0
 [<c011bf04>] kprobe_handler+0x1c9/0x20b
 [<c011c1cd>] kprobe_exceptions_notify+0x54/0x19b
 [<c01348a1>] notifier_call_chain+0x17/0x2e

It looks like the __bio_ino embedded-C function is not performing any
safety checks on the pointer chains it is chasing.  A basic first step
would be to use the deref() macro from runtime/oc2c-runtime.h.

- FChE

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