From: Jiayuan Chen <jiayuan.chen@linux.dev>
To: Michal Hocko <mhocko@suse.com>
Cc: bpf@vger.kernel.org, Emil Tsalapatis <emil@etsalapatis.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Clark Williams <clrkwllms@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
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
Date: Mon, 24 Aug 2026 20:44:18 +0800 [thread overview]
Message-ID: <de12ff1b-2f7c-4efe-ba1f-95e0b8d259f2@linux.dev> (raw)
In-Reply-To: <aow4YNCDa0gDwbfj@tiehlicka>
On 8/24/26 8:26 PM, Michal Hocko wrote:
> 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.
Agreed, bpf_map_alloc_pages() is designed to be safe to run in any context.
The commit message should be precise.
next prev parent reply other threads:[~2026-08-24 12:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-21 5:01 [PATCH bpf-next v4 0/4] bpf: arena: handle memory.max on fault-in with reclaim/OOM Jiayuan Chen
2026-08-21 5:06 ` [PATCH bpf-next v4 1/4] bpf: Add a sleepable page allocator for map memory Jiayuan Chen
2026-08-21 5:06 ` [PATCH bpf-next v4 2/4] bpf: arena: allocate the fault-in page outside the lock Jiayuan Chen
2026-08-21 5:59 ` bot+bpf-ci
2026-08-21 10:31 ` Jiayuan Chen
2026-08-21 5:06 ` [PATCH bpf-next v4 3/4] selftests/bpf: Add read_cgroup_file() to cgroup_helpers Jiayuan Chen
2026-08-21 5:06 ` [PATCH bpf-next v4 4/4] selftests/bpf: Add a test for arena fault-in under memory.max Jiayuan Chen
2026-08-21 5:59 ` bot+bpf-ci
2026-08-24 12:26 ` [PATCH bpf-next v4 1/4] bpf: Add a sleepable page allocator for map memory Michal Hocko
2026-08-24 12:44 ` Jiayuan Chen [this message]
2026-08-24 13:01 ` Michal Hocko
2026-08-24 13:11 ` Kumar Kartikeya Dwivedi
2026-08-24 13:55 ` Michal Hocko
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