From: Matthew Wilcox <willy@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Jia-Ju Bai <baijiaju1990@gmail.com>,
penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
akpm@linux-foundation.org, linux-mm@kvack.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Can kfree() sleep at runtime?
Date: Thu, 31 May 2018 07:14:52 -0700 [thread overview]
Message-ID: <20180531141452.GC30221@bombadil.infradead.org> (raw)
In-Reply-To: <01000163b68a8026-56fb6a35-040b-4af9-8b73-eb3b4a41c595-000000@email.amazonses.com>
On Thu, May 31, 2018 at 02:12:00PM +0000, Christopher Lameter wrote:
> On Thu, 31 May 2018, Matthew Wilcox wrote:
>
> > On Thu, May 31, 2018 at 09:10:07PM +0800, Jia-Ju Bai wrote:
> > > 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
> >
> > Here's your bug. Coming from kfree(), we can't end up in the
> > split_large_page() path. __change_page_attr may be called in several
> > different circumstances in which it would have to split a large page,
> > but the path from kfree() is not one of them.
>
> 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).
next prev parent reply other threads:[~2018-05-31 14:14 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-31 13:10 Jia-Ju Bai
2018-05-31 14:08 ` Matthew Wilcox
2018-05-31 14:12 ` Christopher Lameter
2018-05-31 14:14 ` Matthew Wilcox [this message]
2018-05-31 14:30 ` Christopher Lameter
2018-06-01 1:22 ` Jia-Ju Bai
2018-06-01 1:34 ` Nadav Amit
2018-06-01 1:12 ` Jia-Ju Bai
2018-05-31 14:09 ` Christopher Lameter
2018-06-01 1:18 ` Jia-Ju Bai
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