Can kfree() sleep at runtime?

[Jia-Ju Bai <baijiaju1990@gmail.com>]

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Hello,

I write a static analysis tool (DSAC), and it finds that kfree() can sleep.

Here is the call path for kfree().
Please look at it *from the bottom up*.

[FUNC] alloc_pages(GFP_KERNEL)
arch/x86/mm/pageattr.c, 756: alloc_pages in split_large_page
arch/x86/mm/pageattr.c, 1283: split_large_page in __change_page_attr
arch/x86/mm/pageattr.c, 1391: __change_page_attr in 
__change_page_attr_set_clr
arch/x86/mm/pageattr.c, 2014: __change_page_attr_set_clr in __set_pages_np
arch/x86/mm/pageattr.c, 2034: __set_pages_np in __kernel_map_pages
./include/linux/mm.h, 2488: __kernel_map_pages in kernel_map_pages
mm/page_alloc.c, 1074: kernel_map_pages in free_pages_prepare
mm/page_alloc.c, 1264: free_pages_prepare in __free_pages_ok
mm/page_alloc.c, 4312: __free_pages_ok in __free_pages
mm/slub.c, 3914: __free_pages in kfree

I always have an impression that kfree() never sleeps, so I feel 
confused here.
So could someone please help me to find the mistake?
Thanks in advance :)

Best wishes,
Jia-Ju Bai

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