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Tue, 24 Mar 2026 07:32:03 -0700 (PDT) Received: from localhost ([2620:10d:c092:500::5:8a8a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-487116f17f3sm51632665e9.1.2026.03.24.07.32.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Mar 2026 07:32:03 -0700 (PDT) From: Mykyta Yatsenko To: oskar@gerlicz.space Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com, yatsenko@meta.com Subject: Re: [PATCH bpf-next v5 2/5] bpf: Add sleepable support for classic tracepoint programs In-Reply-To: References: <629d0324276759a1bda71248e93a99e2@gerlicz.space> <7560779e22010c1907fe6045ef595d19@gerlicz.space> Date: Tue, 24 Mar 2026 14:32:02 +0000 Message-ID: <877br1jo2l.fsf@gmail.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=utf-8 Content-Transfer-Encoding: quoted-printable Mykyta Yatsenko writes: > On 3/23/26 9:26 PM, oskar@gerlicz.space wrote: >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (unlikely(this_cpu_inc_return(= bpf_prog_active) !=3D 1)) { >>=20 >> Hi, >>=20 >> A question regarding the recursion handling. >>=20 >> Even with migrate_disable(), this still runs in a preemptible and >> sleepable context. So if a task increments bpf_prog_active and then >> sleeps, another task could run on the same CPU and also modify the >> same per-CPU counter. >>=20 >> Would this interleaving affect recursion tracking correctness, or is >> this accounted for? >>=20 >> Oskar Gerlicz Kowalczuk >>=20 > We discussed this with Kumar in the sibling thread, the initial thinking= =20 > behind this was that second task incrementing this counter won't see 1,=20 > so it's going to > > this_cpu_dec(bpf_prog_active); > return 0; > > I'm reworking this for the next version. The initial thinking behind this was that the second task incrementing this= counter won't see 1, so it's going to this_cpu_dec(bpf_prog_active); return 0; I'm reworking this for the next version, as discussed in the sibling thread= with Kumar.