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RE: Summary of nightly tests 20061109
- From: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>
- To: "William Cohen" <wcohen at redhat dot com>, "Martin Hunt" <hunt at redhat dot com>
- Cc: "SystemTAP" <systemtap at sources dot redhat dot com>
- Date: Mon, 13 Nov 2006 18:17:21 -0800
- Subject: RE: Summary of nightly tests 20061109
On Thursday, November 09, 2006 11:19 AM, William Cohen wrote:
> RHLE4 U4 ia64
> Kernel: Linux 2.6.9-42.0.3.EL #1 SMP Mon Sep 25 17:14:34 EDT 2006
> ia64 ia64 ia64 GNU/Linux
> [...]
> The earliest record of staprun causing unaligned accesses on the ia64
> machine is Nov 5. See things like the following in the systemtap.log
> output of dejagnu.
> [...]
> staprun(9115): unaligned access to 0x2000000000338014,
ip=0x4000000000007c01
> staprun(9115): unaligned access to 0x200000000033801c,
ip=0x4000000000007c10
> staprun(9115): unaligned access to 0x2000000000338024,
ip=0x4000000000007c01
> staprun(9115): unaligned access to 0x200000000033802c,
ip=0x4000000000007c10
In do_kernel_symbols (runtime/stpd/symbols.c), there are these lines:
144: sym_base = malloc(MAX_SYMBOLS*sizeof(struct
_stp_symbol)+sizeof(int));
[...]
154: *(int *)sym_base = STP_SYMBOLS;
155: syms = (struct _stp_symbol *)(sym_base + sizeof(int));
[...]
178: syms[i].addr = addr;
179: syms[i].symbol = (char *)(dataptr - data);
The ips 7c01 and 7c10 correspond to lines 178 and 179. Line 144 will
return an 8-byte aligned pointer, and then 155 adds 4 to it. From then
on, all access to 8-byte fields through 'syms' will be misaligned.
There's a logging rate limiter that's saving us from seeing more than
four of the same message, thankfully.
One potential solution is to make the transport command a long instead
of int. Such a fix would require changes to the whole transport layer,
though, so I'll leave it to Martin to decide what to do...
Josh