From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 920196B0005 for ; Thu, 31 May 2018 09:10:30 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id z5-v6so12684835pfz.6 for ; Thu, 31 May 2018 06:10:30 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id o70-v6sor13255484pfo.38.2018.05.31.06.10.28 for (Google Transport Security); Thu, 31 May 2018 06:10:28 -0700 (PDT) From: Jia-Ju Bai Subject: Can kfree() sleep at runtime? Message-ID: <30ecafd7-ed61-907b-f924-77fc37dcc753@gmail.com> Date: Thu, 31 May 2018 21:10:07 +0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="------------6CDAB3B1D5538EEDBFDCB4E4" Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, Linux Kernel Mailing List This is a multi-part message in MIME format. --------------6CDAB3B1D5538EEDBFDCB4E4 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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 --------------6CDAB3B1D5538EEDBFDCB4E4 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 7bit 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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