linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Daniel Palmer <daniel@0x0f.com>
To: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Guenter Roeck <linux@roeck-us.net>,
	 Brendan Jackman <jackmanb@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@suse.com>,
	 Suren Baghdasaryan <surenb@google.com>,
	Vlastimil Babka <vbabka@suse.cz>, Zi Yan <ziy@nvidia.com>,
	 linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	kernel-team@meta.com
Subject: Re: [PATCH v2] mm/page_alloc: Report 1 as zone_batchsize for !CONFIG_MMU
Date: Thu, 18 Dec 2025 21:30:42 +0900	[thread overview]
Message-ID: <CAFr9PXnK+WCOGYs_e5HiCiwxN1SdjGhmR3DOi8w0BYRqooQONA@mail.gmail.com> (raw)
In-Reply-To: <20251218083200.2435789-1-joshua.hahnjy@gmail.com>

Hi Joshua,

On Thu, 18 Dec 2025 at 17:32, Joshua Hahn <joshua.hahnjy@gmail.com> wrote:
>
> Commit 2783088ef24e ("mm/page_alloc: prevent reporting pcp->batch = 0")
> moved the error handling (0-handling) of zone_batchsize from its
> callers to inside the function. However, the commit left out the error
> handling for the NOMMU case, leading to deadlocks on NOMMU systems.
>
> For NOMMU systems, return 1 instead of 0 for zone_batchsize, which restores
> the previous deadlock-free behavior.

Tested this on my 68000 setup, filled the memory to cause an OOM and I
got OOM instead of deadlock as expected.

Tested-by: Daniel Palmer <daniel@thingy.jp>

FWIW There was a BoF about NOMMU at LPC last week and I did mention to
the people presenting that seem to be using NOMMU in real world
applications that NOMMU was broken in mainline. I hoped they would
have chimed in on this..

Thanks!

Daniel


  parent reply	other threads:[~2025-12-18 12:30 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-18  8:31 Joshua Hahn
2025-12-18 11:23 ` Vlastimil Babka
2025-12-18 12:30 ` Daniel Palmer [this message]
2025-12-18 15:39   ` Guenter Roeck
2025-12-19 15:51   ` Hajime Tazaki
2025-12-18 15:39 ` Guenter Roeck
2025-12-20  2:41 ` SeongJae Park

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAFr9PXnK+WCOGYs_e5HiCiwxN1SdjGhmR3DOi8w0BYRqooQONA@mail.gmail.com \
    --to=daniel@0x0f.com \
    --cc=akpm@linux-foundation.org \
    --cc=hannes@cmpxchg.org \
    --cc=jackmanb@google.com \
    --cc=joshua.hahnjy@gmail.com \
    --cc=kernel-team@meta.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux@roeck-us.net \
    --cc=mhocko@suse.com \
    --cc=surenb@google.com \
    --cc=vbabka@suse.cz \
    --cc=ziy@nvidia.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox