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sched_ext: Always bounce scx_disable() through irq_work

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scx_disable() directly called kthread_queue_work() which can acquire
worker->lock, pi_lock and rq->__lock. This made scx_disable() unsafe to
call while holding locks that conflict with this chain - in particular,
scx_claim_exit() calls scx_disable() for each descendant while holding
scx_sched_lock, which nests inside rq->__lock in scx_bypass().

The error path (scx_vexit()) was already bouncing through irq_work to
avoid this issue. Generalize the pattern to all scx_disable() calls by
always going through irq_work. irq_work_queue() is lockless and safe to
call from any context, and the actual kthread_queue_work() call happens
in the irq_work handler outside any locks.

Rename error_irq_work to disable_irq_work to reflect the broader usage.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-03-10 07:12:21 -10:00
parent b5bc043505
commit f4a6c506d1
2 changed files with 7 additions and 7 deletions
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12
kernel/sched/ext.c
View File

@ -4498,7 +4498,7 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
struct scx_dispatch_q *dsq;
int cpu, node;
irq_work_sync(&sch->error_irq_work);
irq_work_sync(&sch->disable_irq_work);
kthread_destroy_worker(sch->helper);
timer_shutdown_sync(&sch->bypass_lb_timer);
@ -5679,7 +5679,7 @@ static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind)
{
guard(preempt)();
if (scx_claim_exit(sch, kind))
kthread_queue_work(sch->helper, &sch->disable_work);
irq_work_queue(&sch->disable_irq_work);
}
static void dump_newline(struct seq_buf *s)
@ -6012,9 +6012,9 @@ static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei,
trunc_marker, sizeof(trunc_marker));
}
static void scx_error_irq_workfn(struct irq_work *irq_work)
static void scx_disable_irq_workfn(struct irq_work *irq_work)
{
struct scx_sched *sch = container_of(irq_work, struct scx_sched, error_irq_work);
struct scx_sched *sch = container_of(irq_work, struct scx_sched, disable_irq_work);
struct scx_exit_info *ei = sch->exit_info;
if (ei->kind >= SCX_EXIT_ERROR)
@ -6048,7 +6048,7 @@ static bool scx_vexit(struct scx_sched *sch,
ei->kind = kind;
ei->reason = scx_exit_reason(ei->kind);
irq_work_queue(&sch->error_irq_work);
irq_work_queue(&sch->disable_irq_work);
return true;
}
@ -6184,7 +6184,7 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops,
sch->slice_dfl = SCX_SLICE_DFL;
atomic_set(&sch->exit_kind, SCX_EXIT_NONE);
init_irq_work(&sch->error_irq_work, scx_error_irq_workfn);
init_irq_work(&sch->disable_irq_work, scx_disable_irq_workfn);
kthread_init_work(&sch->disable_work, scx_disable_workfn);
timer_setup(&sch->bypass_lb_timer, scx_bypass_lb_timerfn, 0);
sch->ops = *ops;

2
kernel/sched/ext_internal.h
View File

@ -1042,7 +1042,7 @@ struct scx_sched {
struct kobject kobj;
struct kthread_worker *helper;
struct irq_work error_irq_work;
struct irq_work disable_irq_work;
struct kthread_work disable_work;
struct timer_list bypass_lb_timer;
struct rcu_work rcu_work;