From: Tejun Heo <tj@kernel.org> mainline inclusion from mainline-v6.12-rc1 commit 36454023f50b2aadd25b7f47c50b5edc0c59e1c0 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- When some SCX operations are in flight, it is known that the subject task's rq lock is held throughout which makes it safe to access certain fields of the task - e.g. its current task_group. We want to add SCX kfunc helpers that can make use of this guarantee - e.g. to help determining the currently associated CPU cgroup from the task's current task_group. As it'd be dangerous call such a helper on a task which isn't rq lock protected, the helper should be able to verify the input task and reject accordingly. This patch adds sched_ext_entity.kf_tasks[] that track the tasks which are currently being operated on by a terminal SCX operation. The new SCX_CALL_OP_[2]TASK[_RET]() can be used when invoking SCX operations which take tasks as arguments and the scx_kf_allowed_on_arg_tasks() can be used by kfunc helpers to verify the input task status. Note that as sched_ext_entity.kf_tasks[] can't handle nesting, the tracking is currently only limited to terminal SCX operations. If needed in the future, this restriction can be removed by moving the tracking to the task side with a couple per-task counters. v2: Updated to reflect the addition of SCX_KF_SELECT_CPU. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- include/linux/sched/ext.h | 2 + kernel/sched/ext.c | 91 +++++++++++++++++++++++++++++++-------- 2 files changed, 76 insertions(+), 17 deletions(-) diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h index 6f1a4977e9f8..74341dbc6a19 100644 --- a/include/linux/sched/ext.h +++ b/include/linux/sched/ext.h @@ -106,6 +106,7 @@ enum scx_kf_mask { __SCX_KF_RQ_LOCKED = SCX_KF_DISPATCH | SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU | SCX_KF_REST, + __SCX_KF_TERMINAL = SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU | SCX_KF_REST, }; /* @@ -120,6 +121,7 @@ struct sched_ext_entity { s32 sticky_cpu; s32 holding_cpu; u32 kf_mask; /* see scx_kf_mask above */ + struct task_struct *kf_tasks[2]; /* see SCX_CALL_OP_TASK() */ atomic_long_t ops_state; struct list_head runnable_node; /* rq->scx.runnable_list */ diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index c48b31699080..f362b037161a 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -821,6 +821,47 @@ do { \ __ret; \ }) +/* + * Some kfuncs are allowed only on the tasks that are subjects of the + * in-progress scx_ops operation for, e.g., locking guarantees. To enforce such + * restrictions, the following SCX_CALL_OP_*() variants should be used when + * invoking scx_ops operations that take task arguments. These can only be used + * for non-nesting operations due to the way the tasks are tracked. + * + * kfuncs which can only operate on such tasks can in turn use + * scx_kf_allowed_on_arg_tasks() to test whether the invocation is allowed on + * the specific task. + */ +#define SCX_CALL_OP_TASK(mask, op, task, args...) \ +do { \ + BUILD_BUG_ON((mask) & ~__SCX_KF_TERMINAL); \ + current->scx.kf_tasks[0] = task; \ + SCX_CALL_OP(mask, op, task, ##args); \ + current->scx.kf_tasks[0] = NULL; \ +} while (0) + +#define SCX_CALL_OP_TASK_RET(mask, op, task, args...) \ +({ \ + __typeof__(scx_ops.op(task, ##args)) __ret; \ + BUILD_BUG_ON((mask) & ~__SCX_KF_TERMINAL); \ + current->scx.kf_tasks[0] = task; \ + __ret = SCX_CALL_OP_RET(mask, op, task, ##args); \ + current->scx.kf_tasks[0] = NULL; \ + __ret; \ +}) + +#define SCX_CALL_OP_2TASKS_RET(mask, op, task0, task1, args...) \ +({ \ + __typeof__(scx_ops.op(task0, task1, ##args)) __ret; \ + BUILD_BUG_ON((mask) & ~__SCX_KF_TERMINAL); \ + current->scx.kf_tasks[0] = task0; \ + current->scx.kf_tasks[1] = task1; \ + __ret = SCX_CALL_OP_RET(mask, op, task0, task1, ##args); \ + current->scx.kf_tasks[0] = NULL; \ + current->scx.kf_tasks[1] = NULL; \ + __ret; \ +}) + /* @mask is constant, always inline to cull unnecessary branches */ static __always_inline bool scx_kf_allowed(u32 mask) { @@ -850,6 +891,22 @@ static __always_inline bool scx_kf_allowed(u32 mask) return true; } +/* see SCX_CALL_OP_TASK() */ +static __always_inline bool scx_kf_allowed_on_arg_tasks(u32 mask, + struct task_struct *p) +{ + if (!scx_kf_allowed(mask)) + return false; + + if (unlikely((p != current->scx.kf_tasks[0] && + p != current->scx.kf_tasks[1]))) { + scx_ops_error("called on a task not being operated on"); + return false; + } + + return true; +} + /* * SCX task iterator. @@ -1346,7 +1403,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, WARN_ON_ONCE(*ddsp_taskp); *ddsp_taskp = p; - SCX_CALL_OP(SCX_KF_ENQUEUE, enqueue, p, enq_flags); + SCX_CALL_OP_TASK(SCX_KF_ENQUEUE, enqueue, p, enq_flags); *ddsp_taskp = NULL; if (p->scx.ddsp_dsq_id != SCX_DSQ_INVALID) @@ -1431,7 +1488,7 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags add_nr_running(rq, 1); if (SCX_HAS_OP(runnable)) - SCX_CALL_OP(SCX_KF_REST, runnable, p, enq_flags); + SCX_CALL_OP_TASK(SCX_KF_REST, runnable, p, enq_flags); do_enqueue_task(rq, p, enq_flags, sticky_cpu); } @@ -1457,7 +1514,7 @@ static void ops_dequeue(struct task_struct *p, u64 deq_flags) BUG(); case SCX_OPSS_QUEUED: if (SCX_HAS_OP(dequeue)) - SCX_CALL_OP(SCX_KF_REST, dequeue, p, deq_flags); + SCX_CALL_OP_TASK(SCX_KF_REST, dequeue, p, deq_flags); if (atomic_long_try_cmpxchg(&p->scx.ops_state, &opss, SCX_OPSS_NONE)) @@ -1506,11 +1563,11 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags */ if (SCX_HAS_OP(stopping) && task_current(rq, p)) { update_curr_scx(rq); - SCX_CALL_OP(SCX_KF_REST, stopping, p, false); + SCX_CALL_OP_TASK(SCX_KF_REST, stopping, p, false); } if (SCX_HAS_OP(quiescent)) - SCX_CALL_OP(SCX_KF_REST, quiescent, p, deq_flags); + SCX_CALL_OP_TASK(SCX_KF_REST, quiescent, p, deq_flags); if (deq_flags & SCX_DEQ_SLEEP) p->scx.flags |= SCX_TASK_DEQD_FOR_SLEEP; @@ -1530,7 +1587,7 @@ static void yield_task_scx(struct rq *rq) struct task_struct *p = rq->curr; if (SCX_HAS_OP(yield)) - SCX_CALL_OP_RET(SCX_KF_REST, yield, p, NULL); + SCX_CALL_OP_2TASKS_RET(SCX_KF_REST, yield, p, NULL); else p->scx.slice = 0; } @@ -1540,7 +1597,7 @@ static bool yield_to_task_scx(struct rq *rq, struct task_struct *to) struct task_struct *from = rq->curr; if (SCX_HAS_OP(yield)) - return SCX_CALL_OP_RET(SCX_KF_REST, yield, from, to); + return SCX_CALL_OP_2TASKS_RET(SCX_KF_REST, yield, from, to); else return false; } @@ -2096,7 +2153,7 @@ static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first) /* see dequeue_task_scx() on why we skip when !QUEUED */ if (SCX_HAS_OP(running) && (p->scx.flags & SCX_TASK_QUEUED)) - SCX_CALL_OP(SCX_KF_REST, running, p); + SCX_CALL_OP_TASK(SCX_KF_REST, running, p); clr_task_runnable(p, true); @@ -2160,7 +2217,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p) /* see dequeue_task_scx() on why we skip when !QUEUED */ if (SCX_HAS_OP(stopping) && (p->scx.flags & SCX_TASK_QUEUED)) - SCX_CALL_OP(SCX_KF_REST, stopping, p, true); + SCX_CALL_OP_TASK(SCX_KF_REST, stopping, p, true); /* * If we're being called from put_prev_task_balance(), balance_scx() may @@ -2382,8 +2439,8 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag WARN_ON_ONCE(*ddsp_taskp); *ddsp_taskp = p; - cpu = SCX_CALL_OP_RET(SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU, - select_cpu, p, prev_cpu, wake_flags); + cpu = SCX_CALL_OP_TASK_RET(SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU, + select_cpu, p, prev_cpu, wake_flags); *ddsp_taskp = NULL; if (ops_cpu_valid(cpu, "from ops.select_cpu()")) return cpu; @@ -2416,8 +2473,8 @@ static void set_cpus_allowed_scx(struct task_struct *p, * designation pointless. Cast it away when calling the operation. */ if (SCX_HAS_OP(set_cpumask)) - SCX_CALL_OP(SCX_KF_REST, set_cpumask, p, - (struct cpumask *)p->cpus_ptr); + SCX_CALL_OP_TASK(SCX_KF_REST, set_cpumask, p, + (struct cpumask *)p->cpus_ptr); } static void reset_idle_masks(void) @@ -2652,7 +2709,7 @@ static void scx_ops_enable_task(struct task_struct *p) */ set_task_scx_weight(p); if (SCX_HAS_OP(enable)) - SCX_CALL_OP(SCX_KF_REST, enable, p); + SCX_CALL_OP_TASK(SCX_KF_REST, enable, p); scx_set_task_state(p, SCX_TASK_ENABLED); if (SCX_HAS_OP(set_weight)) @@ -2806,7 +2863,7 @@ static void reweight_task_scx(struct rq *rq, struct task_struct *p, const struct set_task_scx_weight(p); if (SCX_HAS_OP(set_weight)) - SCX_CALL_OP(SCX_KF_REST, set_weight, p, p->scx.weight); + SCX_CALL_OP_TASK(SCX_KF_REST, set_weight, p, p->scx.weight); } static void prio_changed_scx(struct rq *rq, struct task_struct *p, int oldprio) @@ -2822,8 +2879,8 @@ static void switching_to_scx(struct rq *rq, struct task_struct *p) * different scheduler class. Keep the BPF scheduler up-to-date. */ if (SCX_HAS_OP(set_cpumask)) - SCX_CALL_OP(SCX_KF_REST, set_cpumask, p, - (struct cpumask *)p->cpus_ptr); + SCX_CALL_OP_TASK(SCX_KF_REST, set_cpumask, p, + (struct cpumask *)p->cpus_ptr); } static void switched_from_scx(struct rq *rq, struct task_struct *p) -- 2.34.1