Pass struct scx_enable_cmd to scx_enable() rather than unpacking @ops at every call site and re-packing into a fresh cmd inside. bpf_scx_reg() now builds the cmd on its stack and hands it in; scx_enable() just wires up the kthread work and waits. Relocate struct scx_enable_cmd above scx_alloc_and_add_sched() so upcoming patches that also want the cmd can see it. No behavior change.
Unified · Split
| @@ -6529,6 +6529,19 @@ static struct scx_sched_pnode *alloc_pnode(struct scx_sched *sch, int node) · 6528 unmodified lines | ||
| 6529 | 6529 | return pnode; |
| 6530 | 6530 | } |
| 6531 | 6531 | |
| 6532 | +/* | |
| 6533 | + * scx_enable() is offloaded to a dedicated system-wide RT kthread to avoid | |
| 6534 | + * starvation. During the READY -> ENABLED task switching loop, the calling | |
| 6535 | + * thread's sched_class gets switched from fair to ext. As fair has higher | |
| 6536 | + * priority than ext, the calling thread can be indefinitely starved under | |
| 6537 | + * fair-class saturation, leading to a system hang. | |
| 6538 | + */ | |
| 6539 | +struct scx_enable_cmd { | |
| 6540 | + struct kthread_work work; | |
| 6541 | + struct sched_ext_ops *ops; | |
| 6542 | + int ret; | |
| 6543 | +}; | |
| 6544 | + | |
| 6532 | 6545 | /* |
| 6533 | 6546 | * Allocate and initialize a new scx_sched. @cgrp's reference is always |
| 6534 | 6547 | * consumed whether the function succeeds or fails. |
| @@ -6771,19 +6784,6 @@ static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops) · 236 unmodified lines | ||
| 6771 | 6784 | return 0; |
| 6772 | 6785 | } |
| 6773 | 6786 | |
| 6774 | −/* | |
| 6775 | − * scx_enable() is offloaded to a dedicated system-wide RT kthread to avoid | |
| 6776 | − * starvation. During the READY -> ENABLED task switching loop, the calling | |
| 6777 | − * thread's sched_class gets switched from fair to ext. As fair has higher | |
| 6778 | − * priority than ext, the calling thread can be indefinitely starved under | |
| 6779 | − * fair-class saturation, leading to a system hang. | |
| 6780 | − */ | |
| 6781 | −struct scx_enable_cmd { | |
| 6782 | − struct kthread_work work; | |
| 6783 | − struct sched_ext_ops *ops; | |
| 6784 | − int ret; | |
| 6785 | −}; | |
| 6786 | − | |
| 6787 | 6787 | static void scx_root_enable_workfn(struct kthread_work *work) |
| 6788 | 6788 | { |
| 6789 | 6789 | struct scx_enable_cmd *cmd = container_of(work, struct scx_enable_cmd, work); |
| @@ -7368,11 +7368,10 @@ static s32 __init scx_cgroup_lifetime_notifier_init(void) · 578 unmodified lines | ||
| 7368 | 7368 | core_initcall(scx_cgroup_lifetime_notifier_init); |
| 7369 | 7369 | #endif /* CONFIG_EXT_SUB_SCHED */ |
| 7370 | 7370 | |
| 7371 | −static s32 scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) | |
| 7371 | +static s32 scx_enable(struct scx_enable_cmd *cmd, struct bpf_link *link) | |
| 7372 | 7372 | { |
| 7373 | 7373 | static struct kthread_worker *helper; |
| 7374 | 7374 | static DEFINE_MUTEX(helper_mutex); |
| 7375 | − struct scx_enable_cmd cmd; | |
| 7376 | 7375 | |
| 7377 | 7376 | if (!cpumask_equal(housekeeping_cpumask(HK_TYPE_DOMAIN), |
| 7378 | 7377 | cpu_possible_mask)) { |
| @@ -7396,16 +7395,15 @@ static s32 scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) · 17 unmodified lines | ||
| 7396 | 7395 | } |
| 7397 | 7396 | |
| 7398 | 7397 | #ifdef CONFIG_EXT_SUB_SCHED |
| 7399 | − if (ops->sub_cgroup_id > 1) | |
| 7400 | − kthread_init_work(&cmd.work, scx_sub_enable_workfn); | |
| 7398 | + if (cmd->ops->sub_cgroup_id > 1) | |
| 7399 | + kthread_init_work(&cmd->work, scx_sub_enable_workfn); | |
| 7401 | 7400 | else |
| 7402 | 7401 | #endif /* CONFIG_EXT_SUB_SCHED */ |
| 7403 | − kthread_init_work(&cmd.work, scx_root_enable_workfn); | |
| 7404 | − cmd.ops = ops; | |
| 7402 | + kthread_init_work(&cmd->work, scx_root_enable_workfn); | |
| 7405 | 7403 | |
| 7406 | − kthread_queue_work(READ_ONCE(helper), &cmd.work); | |
| 7407 | − kthread_flush_work(&cmd.work); | |
| 7408 | − return cmd.ret; | |
| 7404 | + kthread_queue_work(READ_ONCE(helper), &cmd->work); | |
| 7405 | + kthread_flush_work(&cmd->work); | |
| 7406 | + return cmd->ret; | |
| 7409 | 7407 | } |
| 7410 | 7408 | |
| 7411 | 7409 | |
| @@ -7577,7 +7575,9 @@ static int bpf_scx_check_member(const struct btf_type *t, · 165 unmodified lines | ||
| 7577 | 7575 | |
| 7578 | 7576 | static int bpf_scx_reg(void *kdata, struct bpf_link *link) |
| 7579 | 7577 | { |
| 7580 | − return scx_enable(kdata, link); | |
| 7578 | + struct scx_enable_cmd cmd = { .ops = kdata }; | |
| 7579 | + | |
| 7580 | + return scx_enable(&cmd, link); | |
| 7581 | 7581 | } |
| 7582 | 7582 | |
| 7583 | 7583 | static void bpf_scx_unreg(void *kdata, struct bpf_link *link) |