From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32C401B7910; Thu, 9 Jul 2026 22:50:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783637445; cv=none; b=H+YyDdUqxAlzZ+qsXWii8Havk9cHRWf3h8Hu0fRCfx9T74hc97UoLfHfafQSWazz6sWyx5uMMcImbJEfDo0CLx04XO8BQlWRpj+v0aumKAmhiTAHofzXIsXpS3z0HPd34zrUSOXknDJ6m7lmiML0/hdthxGMyjEtaEYhemFwGD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783637445; c=relaxed/simple; bh=6gwGU20dsGHp+PYnGzFRxinKyQq8BeKSkPlbdAltD8E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Pxeq4plLSqihu2rKj9rhbuZeRuoj+sWjNH/ZRVnWY+hUbqqJfskYR5+lxNEVchVMblkiggjnL5Poc6asMzaT4x8KSb8u+wpCXzQKNWbIJZ3ubkY3/fEPvPnm34DV7wPlOw3kpJmukPLOunD16RvNgEnUkN9aDOWCVMVH/O4U890= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lrjAymCs; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lrjAymCs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1D1A1F00A3A; Thu, 9 Jul 2026 22:50:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783637443; bh=FL9n3EWHTffkv0GP/jCWQ4/Ug9iRhn+ugqp0Qzg2iIQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lrjAymCsl9UzHZQjzLaMiGUzrD/8nuzNvVE5zRbFUAQVc7IYnzNEHCT/11hEREQ9Q ScKoqwJvsXotLqAaKz3OOjqbUvSnI1/CNiPoWQ0UuN55eALR67b6mSTcSRPnzqw39p 4/DYCGrgxfzL3rWoWV+0ez7v40r3GRIcFsNxbDZJl4zy0Mx+X8siGD4+hfYrI48G9H KZGhsrz4OrCPgIiY5obVzVUT5sfuDOxaKwY8SuWYUU5WchojMBA8u4hBfkGs676EaV 2QVI45AFzPG9y88j/+ksTUvWUlDtjjZil50IuICmF2yUD/VjmUhJUN5ujvaPeBFHGK ldPfBUSKp/FUw== From: Tejun Heo To: David Vernet , Andrea Righi , Changwoo Min Cc: sched-ext@lists.linux.dev, Emil Tsalapatis , linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH v5 sched_ext/for-7.3 01/33] sched_ext: Assert per-task ops run on the task's owner Date: Thu, 9 Jul 2026 12:50:09 -1000 Message-ID: <20260709225041.1695495-2-tj@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260709225041.1695495-1-tj@kernel.org> References: <20260709225041.1695495-1-tj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A per-task op must be dispatched on the scheduler that owns the task. SCX_CALL_OP_TASK() and its _RET twin take @sch explicitly, and a caller that passes the wrong scheduler would silently run the op on it. Add a WARN_ON_ONCE() that @sch matches the task's owner so such a mismatch is caught rather than hidden. Two sites legitimately target a scheduler other than the task's owner: cgroup_move() runs on the root sched, and scx_sub_init_cancel_task() fires exit_task() on a task not yet associated with @sch. Both switch to the inner __SCX_CALL_OP_TASK(), which dispatches on the explicit @sch without the assert. Signed-off-by: Tejun Heo --- kernel/sched/ext/ext.c | 20 +++++++++++++------- kernel/sched/ext/internal.h | 10 +++++++++- 2 files changed, 22 insertions(+), 8 deletions(-) diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 5241b55a58ec..acc3b43fe88a 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -1436,8 +1436,12 @@ static void scx_dispatch_enqueue(struct scx_sched *sch, struct rq *rq, local_dsq_post_enq(sch, dsq, p, enq_flags); } else { /* - * Task on global/bypass DSQ: leave custody, task on - * non-terminal DSQ: enter custody. + * Global and bypass DSQs are terminal - the task leaves the + * scheduler's custody, so ops.dequeue() fires here. It can run + * without @p's rq lock (finish_dispatch() passes the dispatch + * rq); that's safe because dequeue_task_scx() waits on + * SCX_OPSS_DISPATCHING (see the ops_state note above) and so + * can't race it. A non-terminal DSQ keeps the task in custody. */ if (dsq->id == SCX_DSQ_GLOBAL || dsq->id == SCX_DSQ_BYPASS) call_task_dequeue(sch, rq, p, 0); @@ -3446,8 +3450,9 @@ void scx_sub_init_cancel_task(struct scx_sched *sch, struct task_struct *p) lockdep_assert_held(&p->pi_lock); lockdep_assert_rq_held(task_rq(p)); + /* @p was never associated with @sch, dispatch on the explicit @sch */ if (SCX_HAS_OP(sch, exit_task)) - SCX_CALL_OP_TASK(sch, exit_task, task_rq(p), p, &args); + __SCX_CALL_OP_TASK(sch, ops, exit_task, task_rq(p), p, &args); } void scx_disable_and_exit_task(struct scx_sched *sch, struct task_struct *p) @@ -4184,12 +4189,13 @@ void scx_cgroup_move_task(struct task_struct *p) * cgroup changes. Migration keys off css rather than cgroup identity, * so it can hand an unchanged-cgroup task here with cgrp_moving_from * NULL. Nothing to report to the BPF scheduler then, so skip it and - * keep prep_move and move paired. + * keep prep_move and move paired. Cgroup ops run on the root sched, + * dispatch on the explicit @sch. */ if (SCX_HAS_OP(sch, cgroup_move) && p->scx.cgrp_moving_from) - SCX_CALL_OP_TASK(sch, cgroup_move, task_rq(p), - p, p->scx.cgrp_moving_from, - tg_cgrp(task_group(p))); + __SCX_CALL_OP_TASK(sch, ops, cgroup_move, task_rq(p), + p, p->scx.cgrp_moving_from, + tg_cgrp(task_group(p))); p->scx.cgrp_moving_from = NULL; } diff --git a/kernel/sched/ext/internal.h b/kernel/sched/ext/internal.h index 5ca44ad88786..8aabd92fae3b 100644 --- a/kernel/sched/ext/internal.h +++ b/kernel/sched/ext/internal.h @@ -1810,8 +1810,15 @@ do { \ current->scx.kf_tasks[0] = NULL; \ } while (0) +/* + * A per-task op runs on @task's owner - WARN if @sch isn't it. Sites that must + * target a different scheduler call __SCX_CALL_OP_TASK() directly. + */ #define SCX_CALL_OP_TASK(sch, op, locked_rq, task, args...) \ - __SCX_CALL_OP_TASK(sch, ops, op, locked_rq, task, ##args) +do { \ + WARN_ON_ONCE((sch) != scx_task_sched_rcu(task)); \ + __SCX_CALL_OP_TASK((sch), ops, op, locked_rq, task, ##args); \ +} while (0) /* * Dispatch a task op through the cid-form ops_cid table. Only set_cmask() needs @@ -1824,6 +1831,7 @@ do { \ #define SCX_CALL_OP_TASK_RET(sch, op, locked_rq, task, args...) \ ({ \ __typeof__((sch)->ops.op(task, ##args)) __ret; \ + WARN_ON_ONCE((sch) != scx_task_sched_rcu(task)); \ WARN_ON_ONCE(current->scx.kf_tasks[0]); \ current->scx.kf_tasks[0] = task; \ __ret = SCX_CALL_OP_RET((sch), op, locked_rq, task, ##args); \ -- 2.55.0