workqueue: Process rescuer work items one-by-one using a cursor

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[ Upstream commit e5a30c303b ]

Previously, the rescuer scanned for all matching work items at once and
processed them within a single rescuer thread, which could cause one
blocking work item to stall all others.

Make the rescuer process work items one-by-one instead of slurping all
matches in a single pass.

Break the rescuer loop after finding and processing the first matching
work item, then restart the search to pick up the next. This gives
normal worker threads a chance to process other items which gives them
the opportunity to be processed instead of waiting on the rescuer's
queue and prevents a blocking work item from stalling the rest once
memory pressure is relieved.

Introduce a dummy cursor work item to avoid potentially O(N^2)
rescans of the work list.  The marker records the resume position for
the next scan, eliminating redundant traversals.

Also introduce RESCUER_BATCH to control the maximum number of work items
the rescuer processes in each turn, and move on to other PWQs when the
limit is reached.

Cc: ying chen <yc1082463@gmail.com>
Reported-by: ying chen <yc1082463@gmail.com>
Fixes: e22bee782b ("workqueue: implement concurrency managed dynamic worker pool")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Lai Jiangshan 2025-12-08 21:25:18 +08:00 • committed by Sasha Levin

parent 2178f0587c

commit 00b16c7b17

1 changed files with 59 additions and 16 deletions

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kernel/workqueue.c

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