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Date: Thu, 21 May 2026 07:22:29 -1000
Message-ID: <0ea50f62b8255cc0ff1a96206096746a@kernel.org>
From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>,
	Changwoo Min <changwoo@igalia.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Kumar Kartikeya Dwivedi <memxor@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@kernel.org>,
	Mike Rapoport <rppt@kernel.org>,
	Emil Tsalapatis <emil@etsalapatis.com>,
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	bpf@vger.kernel.org,
	x86@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/8] sched_ext: Sub-allocator over kernel-claimed BPF arena pages
In-Reply-To: <ag66lfvACAEAI9w8@gpd4>
References: <20260520235052.4180316-1-tj@kernel.org>
 <20260520235052.4180316-8-tj@kernel.org>
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Hello,

On Thu, May 21, 2026 at 09:56:05AM +0200, Andrea Righi wrote:
> IIUC, since @page_cnt is sized to cover @size and the new chunk is added empty
> to the pool, gen_pool_alloc() here should always succeed. Should we do:
>
>   if (WARN_ON_ONCE(!kern_va))
>       return NULL;
>
> to catch potential logical bugs / future concurrency / exotic configurations?

Good point. It works for a single caller, but a concurrent one could drain
the new chunk between grow and retry. I'll switch it to a loop.

Thanks.

--
tejun