sched_ext: Remove queued ecaps syncs directly on sched teardown

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scx_discard_ecaps_to_sync() waited for balance_one() to consume a dying
sched's queued ecaps sync, polling with resched_cpu() + msleep(). The wait
is unbounded - the ext dl_server forces picks through sustained fair or RT
load only while ext tasks are queued, so an ext-idle cpu monopolized by a
higher class can stall the teardown indefinitely.

Remove the node directly instead: take all queued nodes, drop the dying
sched's and resplice the rest. Consumption runs under the rq lock and batch
nodes read as on-list throughout, so the producer-side dedup stays correct.

A node that an in-flight scx_process_sync_ecaps() batch holds across a
dispatch-induced rq unlock still needs a wait, but one bounded by that batch
completing rather than by a future balance.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

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This commit is contained in:

Tejun Heo 2026-07-15 13:37:59 -10:00

parent 35f9cbbacb

commit 34e0fbfe67

2 changed files with 43 additions and 26 deletions

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kernel/sched/ext/ext.c

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67

kernel/sched/ext/sub.c

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