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Date: Fri, 03 Jul 2026 11:43:39 +0000
Message-Id: <DJOWRDASVUUV.376L8DP13F1XQ@linux.dev>
Cc: "Harry Yoo (Oracle)" <harry@kernel.org>, "Gregory Price"
 <gourry@gourry.net>, "Alexei Starovoitov" <ast@kernel.org>, "Matthew
 Wilcox" <willy@infradead.org>, "Hao Ge" <hao.ge@linux.dev>,
 <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
 <linux-rt-devel@lists.linux.dev>, <derkling@google.com>,
 <reijiw@google.com>, "Yosry Ahmed" <yosry@kernel.org>
Subject: Re: [PATCH v4 18/18] mm: factor out can_spin_trylock()
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From: "Brendan Jackman" <brendan.jackman@linux.dev>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>, "Brendan Jackman"
 <jackmanb@google.com>, "Andrew Morton" <akpm@linux-foundation.org>, "Suren
 Baghdasaryan" <surenb@google.com>, "Michal Hocko" <mhocko@suse.com>,
 "Johannes Weiner" <hannes@cmpxchg.org>, "Zi Yan" <ziy@nvidia.com>, "Muchun
 Song" <muchun.song@linux.dev>, "Oscar Salvador" <osalvador@suse.de>, "David
 Hildenbrand" <david@kernel.org>, "Lorenzo Stoakes" <ljs@kernel.org>, "Liam
 R. Howlett" <liam@infradead.org>, "Mike Rapoport" <rppt@kernel.org>,
 "Matthew Brost" <matthew.brost@intel.com>, "Joshua Hahn"
 <joshua.hahnjy@gmail.com>, "Rakie Kim" <rakie.kim@sk.com>, "Byungchul Park"
 <byungchul@sk.com>, "Ying Huang" <ying.huang@linux.alibaba.com>, "Alistair
 Popple" <apopple@nvidia.com>, "Hao Li" <hao.li@linux.dev>, "Christoph
 Lameter" <cl@gentwo.org>, "David Rientjes" <rientjes@google.com>, "Roman
 Gushchin" <roman.gushchin@linux.dev>, "Sebastian Andrzej Siewior"
 <bigeasy@linutronix.de>, "Clark Williams" <clrkwllms@kernel.org>, "Steven
 Rostedt" <rostedt@goodmis.org>
References: <20260702-alloc-trylock-v4-0-0af8ff387e80@google.com>
 <20260702-alloc-trylock-v4-18-0af8ff387e80@google.com>
 <1e162a97-1594-495d-b48e-7dafaa0a6d82@kernel.org>
In-Reply-To: <1e162a97-1594-495d-b48e-7dafaa0a6d82@kernel.org>
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On Fri Jul 3, 2026 at 9:32 AM UTC, Vlastimil Babka (SUSE) wrote:
> On 7/2/26 11:49, Brendan Jackman wrote:
>> Deduplicate checks for whether the current context is safe for
>> spin_trylock().
>>=20
>> Does this function really belong in mm/internal.h or is it generic? Not
>> sure. If someone ends up duplicating this logic elsewhere in the kernel,
>> that would be a shame. But goes in some generic header, someone treats
>> it as documentation about where it's guaranteed safe to spin_trylock(),
>> and then it emerges that there are other subtle preconditions that
>> didn't affect the mm usecase, that would be worse. So, just be
>> conservative and keep it local.
>
> Agreed. We could even use page_alloc.h ?

Would be nice to shrink the scope but I think it would be "wrong" for
slub.c to get it from there. It's not to do with the page allocator.