Re: [Crash-utility] crash-5.0: zero-size memory-allocation
From:
Dave Anderson <anderson(a)redhat.com>
...
But your kernel shows cache_cache.buffer_size set to zero -- and the
ASSIGN_SIZE(kmem_cache_s) above dutifully downsized the data structure
size from 204 to zero. Later on, that size was used to allocate a
kmem_cache buffer, which failed when a GETBUF() was called with a
zero-size.
I guess a check could be made above for a zero cache_cache.buffer_size,
but why would that ever be?
Try this:
# crash --no_kmem_cache vmlinux vmcore
which will allow you to get past the kmem_cache initialization.
Then enter:
crash> p cache_cache
Does the "buffer_size" member really show zero?
Yes it seems so!
initialize_task_state: using old defaults
<readmem: 8067a300, KVADDR, "fill_task_struct", 868, (ROE), 86e3f78>
addr: 8067a300 paddr: 67a300 cnt: 868
STATE: TASK_RUNNING (PANIC)
crash> p cache_cache
cache_cache = GETBUF(128 -> 0)
<readmem: 8067f1c0, KVADDR, "gdb_readmem_callback", 204, (ROE), 8ac00d8>
addr: 8067f1c0 paddr: 67f1c0 cnt: 204
$3 = {
array = {0x0, 0x8067f1c4, 0x8067f1c4, 0x0, 0x0, 0x0, 0x0, 0x0,
0xf7813e00, 0xf7849400, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
batchcount = 0,
limit = 0,
shared = 0,
buffer_size = 0,
reciprocal_buffer_size = 0,
flags = 0,
num = 0,
gfporder = 0,
gfpflags = 60,
colour = 120,
colour_off = 8,
slabp_cache = 0x100,
slab_size = 16777216,
dflags = 0,
ctor = 0xf,
name = 0x0,
next = {
next = 0x0,
prev = 0x2
},
nodelists = {0x40}
}
FREEBUF(0)
BTW, you can work around the problem by commenting out the call
to kmem_cache_downsize() in vm_init().
This workaround works ok.
(And if you're using
makedumpfile with excluded pages, hope that the problem I described
above doesn't occur...)
We are not excluding files so this is not a big issue. Also
the --no_kmem_cache lets me open dump and let me do quite many things
already.
- Ville
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