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[109.81.81.112]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c24d8375776sm177761566b.31.2026.08.24.05.26.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 05:26:10 -0700 (PDT) Date: Mon, 24 Aug 2026 14:26:08 +0200 From: Michal Hocko To: Jiayuan Chen Cc: bpf@vger.kernel.org, Emil Tsalapatis , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Ihor Solodrai , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH bpf-next v4 1/4] bpf: Add a sleepable page allocator for map memory Message-ID: References: <20260821050250.35112-1-jiayuan.chen@linux.dev> <20260821050631.39784-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260821050631.39784-1-jiayuan.chen@linux.dev> On Fri 21-08-26 13:06:12, Jiayuan Chen wrote: > bpf_map_alloc_pages() picks the allocator via can_alloc_pages(), a > conservative guess for BPF program context that is always false under > PREEMPT_RT. So even a caller that really is sleepable gets the > non-blocking allocator, which never reclaims and never engages the OOM > machinery. I thought one of the main motivations was reentrancy. As you cannot really assume the context bpf_map_alloc_pages is called from there is an extra care needed so that this doesn't re-enter the allocator from bpf program called from allocator path and deadlock. -- Michal Hocko SUSE Labs