From nobody Sun Oct 5 01:50:08 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AA9752E338D for ; Mon, 11 Aug 2025 21:22:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754947327; cv=none; b=X9pHRlWJuAjpNJyps0t1u49KknsW1wEUd22wsc8ba3Nm3CEL9JsespNcd1SZt6N3AyOt3ljARkXx+m7Ezd4YmaDjveGHI45+/6yVYqhhIui/RIadduYaX+anMcwpgQssrG18gG4DbBizWhzEicNcYIarpXFBSaQDqyQKgoqBL7U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754947327; c=relaxed/simple; bh=rs1rz9seRhodTia6WJevCMyrbdJdVy+CPiy7SqP4Obo=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=orfqd3OgRq73B5qeB0XGoMCM5RCXDirk82yAGr0HtaBI9HRdoYM9vSmD5WUNRXSGC6eSTqFVekXRbX+CFi/tjQQHr7DspvZAu6DAF7h78qbwBB/24YN33zJKWqi/gkcoLuXXG9traxWruk4/5p6unSPmzKFr4A4NdEwYgEXc0Y0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0474F1E8D; Mon, 11 Aug 2025 14:21:57 -0700 (PDT) Received: from e127648.arm.com (unknown [10.57.55.59]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 1FACD3F63F; Mon, 11 Aug 2025 14:22:01 -0700 (PDT) From: Christian Loehle To: tj@kernel.org, arighi@nvidia.com, void@manifault.com Cc: linux-kernel@vger.kernel.org, sched-ext@lists.linux.dev, changwoo@igalia.com, hodgesd@meta.com, mingo@redhat.com, peterz@infradead.org, jake@hillion.co.uk, Christian Loehle Subject: [PATCH v4 1/3] sched_ext: Introduce scx_bpf_cpu_rq_locked() Date: Mon, 11 Aug 2025 22:21:48 +0100 Message-Id: <20250811212150.85759-2-christian.loehle@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250811212150.85759-1-christian.loehle@arm.com> References: <20250811212150.85759-1-christian.loehle@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Most fields in scx_bpf_cpu_rq() assume that its rq_lock is held. Furthermore they become meaningless without rq lock, too. Make a safer version of scx_bpf_cpu_rq() that only returns a rq if we hold rq lock of that rq. Also mark the new scx_bpf_cpu_rq_locked() as returning NULL. Signed-off-by: Christian Loehle --- kernel/sched/ext.c | 22 ++++++++++++++++++++++ tools/sched_ext/include/scx/common.bpf.h | 1 + 2 files changed, 23 insertions(+) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 7dedc9a16281..14706c36ca83 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -7426,6 +7426,27 @@ __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu) return cpu_rq(cpu); } =20 +/** + * scx_bpf_cpu_rq_locked - Fetch the locked rq of a CPU + * @cpu: CPU of the rq + */ +__bpf_kfunc struct rq *scx_bpf_cpu_rq_locked(s32 cpu) +{ + struct rq *rq; + + if (!kf_cpu_valid(cpu, NULL)) + return NULL; + + preempt_disable(); + rq =3D cpu_rq(cpu); + if (rq !=3D scx_locked_rq()) { + scx_kf_error("Accessing not locked rq %d", cpu); + rq =3D NULL; + } + preempt_enable(); + return rq; +} + /** * scx_bpf_task_cgroup - Return the sched cgroup of a task * @p: task of interest @@ -7590,6 +7611,7 @@ BTF_ID_FLAGS(func, scx_bpf_put_cpumask, KF_RELEASE) BTF_ID_FLAGS(func, scx_bpf_task_running, KF_RCU) BTF_ID_FLAGS(func, scx_bpf_task_cpu, KF_RCU) BTF_ID_FLAGS(func, scx_bpf_cpu_rq) +BTF_ID_FLAGS(func, scx_bpf_cpu_rq_locked, KF_RET_NULL) #ifdef CONFIG_CGROUP_SCHED BTF_ID_FLAGS(func, scx_bpf_task_cgroup, KF_RCU | KF_ACQUIRE) #endif diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/inc= lude/scx/common.bpf.h index d4e21558e982..7451491347ed 100644 --- a/tools/sched_ext/include/scx/common.bpf.h +++ b/tools/sched_ext/include/scx/common.bpf.h @@ -91,6 +91,7 @@ s32 scx_bpf_pick_any_cpu(const cpumask_t *cpus_allowed, u= 64 flags) __ksym; bool scx_bpf_task_running(const struct task_struct *p) __ksym; s32 scx_bpf_task_cpu(const struct task_struct *p) __ksym; struct rq *scx_bpf_cpu_rq(s32 cpu) __ksym; +struct rq *scx_bpf_cpu_rq_locked(s32 cpu) __ksym; struct cgroup *scx_bpf_task_cgroup(struct task_struct *p) __ksym __weak; u64 scx_bpf_now(void) __ksym __weak; void scx_bpf_events(struct scx_event_stats *events, size_t events__sz) __k= sym __weak; --=20 2.34.1