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[34.16.192.132]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-32b9be55c1esm13070183a91.9.2025.09.08.13.30.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Sep 2025 13:30:06 -0700 (PDT) Date: Mon, 8 Sep 2025 20:30:01 +0000 From: Peilin Ye To: Shakeel Butt Cc: bpf@vger.kernel.org, Alexei Starovoitov , Johannes Weiner , Tejun Heo , Roman Gushchin , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Kumar Kartikeya Dwivedi , Josh Don , Barret Rhoden , linux-mm@kvack.org Subject: Re: [PATCH bpf] bpf/helpers: Use __GFP_HIGH instead of GFP_ATOMIC in __bpf_async_init() Message-ID: References: <20250905234547.862249-1-yepeilin@google.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Sep 08, 2025 at 10:32:29AM -0700, Shakeel Butt wrote: > On Fri, Sep 05, 2025 at 11:45:46PM +0000, Peilin Ye wrote: > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > > index b9b0c5fe33f6..508b13c24778 100644 > > --- a/kernel/bpf/helpers.c > > +++ b/kernel/bpf/helpers.c > > @@ -1274,8 +1274,14 @@ static int __bpf_async_init(struct bpf_async_kern *async, struct bpf_map *map, u > > goto out; > > } > > > > - /* allocate hrtimer via map_kmalloc to use memcg accounting */ > > - cb = bpf_map_kmalloc_node(map, size, GFP_ATOMIC, map->numa_node); > > + /* Allocate via bpf_map_kmalloc_node() for memcg accounting. Use > > + * __GFP_HIGH instead of GFP_ATOMIC to avoid calling > > + * cgroup_file_notify() if an MEMCG_MAX event is raised by > > + * try_charge_memcg(). This prevents various locking issues, including > > + * double-acquiring locks that may already be held here (e.g., > > + * cgroup_file_kn_lock, rq_lock). > > Too much unnecessary information in the comment. Just mention that we > want nolock allocations and for that we need to remove __GFP_RECLAIM > flags until nolock allocation interfaces are available. Got it - I'll reword in v2. Thanks, Peilin Ye