From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Karl Mehltretter <kmehltretter@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexei Starovoitov <ast@kernel.org>,
Alexander Duyck <alexanderduyck@fb.com>,
David Hildenbrand <david@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Brendan Jackman <brendan.jackman@linux.dev>,
Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
Shakeel Butt <shakeel.butt@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] mm/page_alloc: skip shuffling and reporting for no-lock frees
Date: Tue, 20 Oct 2026 13:09:48 +0200 [thread overview]
Message-ID: <20261020110948.wv_yGAhQ@linutronix.de> (raw)
In-Reply-To: <f5e7b114-2bda-49e3-974f-170211501203@kernel.org>
On 2026-10-20 12:02:01 [+0200], Vlastimil Babka (SUSE) wrote:
> > An instrumented PREEMPT_RT lockdep run forced a random-bit cache refill
> > while calling free_pages_nolock() under a raw spinlock. The unpatched
> > allocator reported:
> >
> > BUG: Invalid wait context
> >
> > The attempted lock was batched_entropy_u64.lock in get_random_u64().
> > Lockdep showed the raw test lock and zone->lock both held.
>
> In slab we solved this by using prandom - commit a1e244a9f177 ("mm/slab: use
> prandom if !allow_spin")
> Could be better?
I hated it at first but now that I looked longer at it, it is not that
bad.
Sebastian
next prev parent reply other threads:[~2026-10-20 11:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-05 6:35 [PATCH] mm/page_alloc: skip shuffling and reporting for no-lock frees Karl Mehltretter
2026-10-20 10:02 ` Vlastimil Babka (SUSE)
2026-10-20 11:09 ` Sebastian Andrzej Siewior [this message]
2026-10-21 5:55 ` Karl Mehltretter
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