linux-kernel - Re: Can kfree() sleep at runtime?

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Message-ID: <01000163b69b6b62-6c5ac940-d6c1-419a-9dc9-697908020c53-000000@email.amazonses.com>
Date:   Thu, 31 May 2018 14:30:29 +0000
From:   Christopher Lameter <cl@...ux.com>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Jia-Ju Bai <baijiaju1990@...il.com>, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Can kfree() sleep at runtime?

On Thu, 31 May 2018, Matthew Wilcox wrote:

> > Freeing a page in the page allocator also was traditionally not sleeping.
> > That has changed?
>
> No.  "Your bug" being "The bug in your static analysis tool".  It probably
> isn't following the data flow correctly (or deeply enough).

Well ok this is not going to trigger for kfree(), this is x86 specific and
requires CONFIG_DEBUG_PAGEALLOC and a free of a page in a huge page.

Ok that is a very contorted situation but how would a static checker deal
with that?