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([143.248.136.81]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b24267397bsm110018405ad.27.2026.03.31.00.20.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 00:20:25 -0700 (PDT) From: Sechang Lim To: leon.hwang@linux.dev Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, haoluo@google.com, john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org, martin.lau@linux.dev, rhkrqnwk98@gmail.com, sdf@fomichev.me, song@kernel.org, sun.jian.kdev@gmail.com, yonghong.song@linux.dev Subject: Re: [PATCH bpf v3] bpf: Fix RCU stall in bpf_fd_array_map_clear() Date: Tue, 31 Mar 2026 07:20:19 +0000 Message-ID: <20260331072019.880589-1-rhkrqnwk98@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <56b3dd26-4110-43c9-8bdb-abc3b7a78435@linux.dev> References: <56b3dd26-4110-43c9-8bdb-abc3b7a78435@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On 31/3/26 13:19, Leon Hwang wrote: > After looking at v2, there's no functional change for v2 -> v3. > > I think, you should send a PING in v2 after some days instead of sending > v3. If v2 will be applied, the tag will be picked up btw. > > Besides, change logs are missing here. You're right, I should have just pinged v2 instead of sending v3. The only change was fixing a CC typo (eddyz78 -> eddyz87), no functional change. Apologies for the missing changelog as well. > Since bpf_fd_array_map_clear() is used across prog_array, > perf_event_array, cgroup_array, and array_of_map, and this patch aims to > avoid RCU stalls for prog_array, does this cond_resched() punish > perf_event_array, cgroup_array, and array_of_map? map_poke_run is only set in prog_array_map_ops, so the expensive path (poke_mutex + map_poke_run) in __fd_array_map_delete_elem() is exclusive to prog_array. For perf_event_array, cgroup_array, and array_of_map, each iteration is just xchg + put_ptr, which is lightweight enough that cond_resched() will not trigger rescheduling in practice. Thanks, Sechang