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From: Shakeel Butt To: Peilin Ye Cc: Andrew Morton , Tejun Heo , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Alexei Starovoitov , Kumar Kartikeya Dwivedi , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: skip cgroup_file_notify if spinning is not allowed Message-ID: References: <20250905201606.66198-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 63184C0008 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: eqg15txp4zdao961pky8aownsp5yh5ji X-HE-Tag: 1757108006-526876 X-HE-Meta: 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 ciC4sRZ3 nqFtRCSW2PueainG6GhYBxtlChabXldv70d6sVJkS8wB3lMGLPwAhh8RFR5HFHgVhs5sbcpPoGTY+wMx8EUuxwfDkfu3DoSbRAIzygrCXZR3vwmVTsx+R0gmHVxlZQAfYYwJ8tBz9plr4bmMGnTBIpcFhUtQigcdBZaWcQSd5TSiOHi1NFs6M4qX3hIrRcAdqac4n3q+QL4GO7vSySyBDzMzmjMv88J/+Lvih5y0vESYJ+Iqr3l3vkTPW5ArZ+LJtl9CDO1Xk0A7b2hw+iJrqRSiBtEzyoktaWDDS1kvci19sqdc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 05, 2025 at 08:48:46PM +0000, Peilin Ye wrote: > On Fri, Sep 05, 2025 at 01:16:06PM -0700, Shakeel Butt wrote: > > Generally memcg charging is allowed from all the contexts including NMI > > where even spinning on spinlock can cause locking issues. However one > > call chain was missed during the addition of memcg charging from any > > context support. That is try_charge_memcg() -> memcg_memory_event() -> > > cgroup_file_notify(). > > > > The possible function call tree under cgroup_file_notify() can acquire > > many different spin locks in spinning mode. Some of them are > > cgroup_file_kn_lock, kernfs_notify_lock, pool_workqeue's lock. So, let's > > just skip cgroup_file_notify() from memcg charging if the context does > > not allow spinning. > > > > Signed-off-by: Shakeel Butt > > Tested-by: Peilin Ye Thanks Peilin. When you post the official patch for __GFP_HIGH in __bpf_async_init(), please add a comment on why __GFP_HIGH is used instead of GFP_ATOMIC. > > The repro described in [1] no longer triggers locking issues after > applying this patch and making __bpf_async_init() use __GFP_HIGH > instead of GFP_ATOMIC: > > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -1275,7 +1275,7 @@ static int __bpf_async_init(struct bpf_async_kern *async, struct bpf_map *map, u > } > > /* allocate hrtimer via map_kmalloc to use memcg accounting */ > - cb = bpf_map_kmalloc_node(map, size, GFP_ATOMIC, map->numa_node); > + cb = bpf_map_kmalloc_node(map, size, __GFP_HIGH, map->numa_node); > if (!cb) { > ret = -ENOMEM; > goto out; > > [1] https://lore.kernel.org/bpf/20250905061919.439648-1-yepeilin@google.com/#t > > Thanks, > Peilin Ye >