Hello,
I have a ARM926 based development board. I am trying to remap 23 MB of
IO memory using ioremap and access with the code snippet below, mm
throws an exception most of the times -
#define MRAM_SIZE 23068672
while(1)
{
offset = test_random() % MRAM_SIZE;
virt_addr = mmem + offset;
page = virt_to_page (virt_addr);
get_page(page);
/* do something */
put_page(page);
}
Exception in linux-kernel ver - 3.1-
[ 116.390625] [<bf0120a4>] (test_init+0xa4/0x114 [test]) from
[<c0008770>] (do_one_initcall+0x94/0x16c)
[ 116.390625] [<c0008770>] (do_one_initcall+0x94/0x16c) from
[<c0043f50>] (sys_init_module+0xd8c/0xfdc)
[ 116.390625] [<c0043f50>] (sys_init_module+0xd8c/0xfdc) from
[<c0009280>] (ret_fast_syscall+0x0/0x2c)
[ 116.390625] Code: e7933280 e3130902 0a000008 e594301c (e5932010)
0xa4 is in test_init (include/linux/mm.h:386).
381 /*
382 * This is safe only because
383 * __split_huge_page_refcount can't run under
384 * get_page().
385 */
386 VM_BUG_ON(atomic_read(&page->first_page->_count) < 0);
387 atomic_inc(&page->first_page->_count);
388 }
389 }
Exception in linux-kernel ver - 3.4.3 -
[ 108.640625] [<c0063ce4>] (__get_page_tail+0x20/0xb0) from
[<bf012084>] (test_init+0x84/0x100 [test])
[ 108.640625] [<bf012084>] (test_init+0x84/0x100 [test]) from
[<c0008770>] (do_one_initcall+0x94/0x16c)
[ 108.640625] [<c0008770>] (do_one_initcall+0x94/0x16c) from
[<c0045330>] (sys_init_module+0x70/0x18c)
[ 108.640625] [<c0045330>] (sys_init_module+0x70/0x18c) from
[<c0009320>] (ret_fast_syscall+0x0/0x2c)
[ 108.640625] Code: 0a000023 e590001c e1530000 0a000020 (e5902010)
Is there a limitation on the size of memory that can be mapped using
ioremap? Looks like, first_page is not configured correctly for memory
mapped using ioremap.
This is a shared memory used by a network device to read and write ip
packets. Can someone please confirm? Any pointers on how to debug and
fix this issue are much appreciated.
Thank you!
Regards, Pratik
[Note: I tried using iotable but situation does not improve.]
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