Hi, I'm getting an immediate crash on 2.6.16 when I run the numastat
command. The machine is a 16-way IBM p575 POWER5+ box. It has 8 NUMA
nodes. Bug is very easy to reproduce on this machine, haven't seen it
on another machine yet.
exception info:
16:mon> e
cpu 0x16: Vector: 300 (Data Access) at [c0000005aa5db890]
pc: c000000000293940: .node_read_numastat+0x7c/0x114
lr: c00000000028aeb4: .sysdev_show+0x48/0x64
sp: c0000005aa5dbb10
msr: 8000000000009032
dar: 68
dsisr: 40000000
current = 0xc0000003b7037800
paca = 0xc0000000005a8780
pid = 14382, comm = numastat
disassembly:
c000000000293930 e9240000 ld r9,0(r4)
c000000000293934 38840008 addi r4,r4,8
c000000000293938 7c0607b4 extsw r6,r0
c00000000029393c 2f86007f cmpwi cr7,r6,127
c000000000293940 e8e90068 ld r7,104(r9) <----------- Null
Ptr in r9
c000000000293944 e8090040 ld r0,64(r9)
c000000000293948 e9690048 ld r11,72(r9)
c00000000029394c e9490050 ld r10,80(r9)
c000000000293950 e9090058 ld r8,88(r9)
c000000000293954 e9290060 ld r9,96(r9)
c000000000293958 7f7b0214 add r27,r27,r0
c00000000029395c 7f5a5a14 add r26,r26,r11
c000000000293960 7f9c3a14 add r28,r28,r7
c000000000293964 7fff5214 add r31,r31,r10
registers:
16:mon> r
R00 = 0000000000000002 R16 = 000000001009b360
R01 = c0000005aa5dbb10 R17 = 0000000000000001
R02 = c00000000077ad10 R18 = 0000000000000000
R03 = c000000b67459000 R19 = 0000000000000000
R04 = c000000f7ffd5cd0 R20 = 000000000000001a
R05 = 0000000000000000 R21 = 00000000101220d0
R06 = 0000000000000002 R22 = 000000001013fdd8
R07 = 000000000000161f R23 = 0000000000001000
R08 = 0000000000001310 R24 = 0000000000000000
R09 = 0000000000000000 R25 = 0000000000001310
R10 = 0000000000000000 R26 = 0000000000000000
R11 = 0000000000000000 R27 = 000000000000161f
R12 = c000000f7ffd5c80 R28 = 000000000000161f
R13 = c0000000005a8780 R29 = 0000000000000000
R14 = 0000000000000000 R30 = c000000000637430
R15 = 0000000000000000 R31 = 0000000000000000
pc = c000000000293940 .node_read_numastat+0x7c/0x114
lr = c00000000028aeb4 .sysdev_show+0x48/0x64
msr = 8000000000009032 cr = 44222488
ctr = c0000000002938c4 xer = 0000000000000010 trap = 300
dar = 0000000000000068 dsisr = 40000000
source code for the function, I believe r9 corresponds to
the struct per_cpu_pageset *ps
static ssize_t node_read_numastat(struct sys_device * dev, char * buf)
{
unsigned long numa_hit, numa_miss, interleave_hit,numa_foreign;
unsigned long local_node, other_node;
int i, cpu;
pg_data_t *pg = NODE_DATA(dev->id);
numa_hit = 0;
numa_miss = 0;
interleave_hit = 0;
numa_foreign = 0;
local_node = 0;
other_node = 0;
for (i = 0; i < MAX_NR_ZONES; i++) {
struct zone *z = &pg->node_zones[i];
for (cpu = 0; cpu < NR_CPUS; cpu++) {
struct per_cpu_pageset *ps = zone_pcp(z,cpu);
numa_hit += ps->numa_hit;
numa_miss += ps->numa_miss;
numa_foreign += ps->numa_foreign;
interleave_hit += ps->interleave_hit;
local_node += ps->local_node;
other_node += ps->other_node;
}
}
...
so the first attempt to dereference 'ps' causes an oops.
Anton B. says that if pg is non-NULL, ps should be non-NULL as well...
Sonny
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