Re: [patch] sched: fix macro -> inline function conversion bug

From: Peter Williams
Date: Mon Jul 03 2006 - 02:06:09 EST


Andrew Morton wrote:
On Mon, 3 Jul 2006 07:25:39 +0200
Ingo Molnar <mingo@xxxxxxx> wrote:

* Andrew Morton <akpm@xxxxxxxx> wrote:

On Sun, 02 Jul 2006 16:27:55 -0700
"Martin J. Bligh" <mbligh@xxxxxxxxxx> wrote:

Panic on NUMA-Q (mm4 was fine). Presumably some new scheduler patch

divide error: 0000 [#1]
8K_STACKS SMP last sysfs file: Modules linked in:
CPU: 1
EIP: 0060:[<c0112b6e>] Not tainted VLI
EFLAGS: 00010046 (2.6.17-mm5-autokern1 #1) EIP is at find_busiest_group+0x1a3/0x47c
eax: 00000000 ebx: 00000007 ecx: 00000000 edx: 00000000
esi: 00000000 edi: e75ff264 ebp: e7405ec8 esp: e7405e58
ds: 007b es: 007b ss: 0068
Process swapper (pid: 0, ti=e7404000 task=c13f8560 task.ti=e7404000)
Stack: e75ff264 00000010 c0119020 00000000 00000000 00000000 00000000 00000000 ffffffff 00000000 00000000 00000001 00000001 00000001 00000080 00000000 00000000 00000200 00000020 00000080 00000000 00000000 e75ff260 c1364960 Call Trace:
[<c0119020>] vprintk+0x5f/0x213
[<c0112efb>] load_balance+0x54/0x1d6
[<c011332d>] rebalance_tick+0xc5/0xe3
[<c01137a3>] scheduler_tick+0x2cb/0x2d3
[<c01215b4>] update_process_times+0x51/0x5d
[<c010c224>] smp_apic_timer_interrupt+0x5a/0x61
[<c0102d5b>] apic_timer_interrupt+0x1f/0x24
[<c01006c0>] default_idle+0x0/0x59
[<c01006f1>] default_idle+0x31/0x59
[<c0100791>] cpu_idle+0x64/0x79
Code: 00 5b 83 f8 1f 89 c6 5f 0f 8e 63 ff ff ff 8b 45 e0 8b 55 e8 01 45 dc 8b 4a 08 89 c2 01 4d d4 c1 e2 07 89 d0 31 d2 89 ce c1 ee 07 <f7> f1 83 7d 9c 00 89 45 e0 74 17 89 45 d8 8b 55 e8 8b 4d a4 8b EIP: [<c0112b6e>] find_busiest_group+0x1a3/0x47c SS:ESP 0068:e7405e58
Yes, Andy's reporting that too. I asked him to identify the file-n-line and he ran away on me.
i checked the scheduler queue and nothing jumped out at me, except the cleanup bug fixed by the patch below. (which should be harmless in this particular case - nr_running should never be smaller than 0 or larger than ~4 billion. A fix is warranted nevertheless.)

Did you work out which divide is getting the div-by-zero? I started at it
a bit and wasn't sure - am getting wildly different code generation over
here.

As far as I can see all divides, except those that rely on group->cpu_power being non zero, in find_busiest_queue() are protected against divide by zero. So this would suggest that initialization of the scheduler group data would be the place to look.

Peter
--
Peter Williams pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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