[Crash-utility] vt->kmem_cache_len_nodes not set

[Dave Anderson]

----- Original Message -----
> Hello Dave,
> 
> I have a s390x dump of a Linux-3.1 kernel where I get the error
> message:
> 
> crash: zero-size memory allocation! (called from 8009f504)
> 
> The error comes from max_cpudata_limit() where GETBUF fails:
> 
>         /*
>          *  Check the shared list of all the nodes.
>          */
>         start_address = (ulong *)GETBUF(sizeof(ulong) *
>         vt->kmem_cache_len_nodes);
> 
> --> vt->kmem_cache_len_nodes = 0
> 
> I debugged the problem a bit and found out that the reason is
> that crash does not set vt->kmem_cache_len_nodes for that dump.
> This attribute seem to be only set in kmem_cache_downsize():
> 
> if (buffer_size < SIZE(kmem_cache_s)) {
>                 if (kernel_symbol_exists("nr_node_ids")) {
>                         get_symbol_data("nr_node_ids", sizeof(int),
>                                 &nr_node_ids);
>                         vt->kmem_cache_len_nodes = nr_node_ids;
>                 } else {
>                         fprintf(fp, "XXX kernel_symbol_exists(\n");
>                         vt->kmem_cache_len_nodes = 1;
>                 }
> 
> In my dump the "if" condition returns false (buffer_size = 768,
> SIZE(kmem_cache_s = 624) therefore vt->kmem_cache_len_nodes is
> not set. Perhaps the content of "cache_cache" is useful to understand
> what is going on:
> 
> print cache_cache
> $7 = {
>   batchcount = 27,
>   limit = 54,
>   shared = 8,
>   buffer_size = 768, <<-----
>   reciprocal_buffer_size = 5592406,
>   flags = 0,
>   num = 5,
>   gfporder = 0,
>   gfpflags = 0,
>   colour = 0,
>   colour_off = 256,
>   slabp_cache = 0x0,
>   slab_size = 256,
>   dflags = 0,
>   ctor = 0,
>   name = 0x667b8e "kmem_cache",
>   next = {
>     next = 0x93b528,
>     prev = 0xff04158
>   },
>   nodelists = 0x93b538,
>   array = {0xff23e00, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
>   0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x
> 0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
>  0x0, 0x0, 0x0, 0x0, 0x0, 0x0}
> }
> 
> Any idea what's wrong here?
> 
> Best Regards
> 
> Michael

Bob does:

  [Crash-utility] "zero-size memory allocation!" is back for Linux 3.1
  https://www.redhat.com/archives/crash-utility/2012-January/msg00086.html

He's working on a patch...

You can use the "crash --no_kmem_cache ..." command line option to get around it.

Dave