workqueue: Report work funcs that trigger automatic CPU_INTENSIVE mechanism

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Workqueue now automatically marks per-cpu work items that hog CPU for too
long as CPU_INTENSIVE, which excludes them from concurrency management and
prevents stalling other concurrency-managed work items. If a work function
keeps running over the thershold, it likely needs to be switched to use an
unbound workqueue.

This patch adds a debug mechanism which tracks the work functions which
trigger the automatic CPU_INTENSIVE mechanism and report them using
pr_warn() with exponential backoff.

v3: Documentation update.

v2: Drop bouncing to kthread_worker for printing messages. It was to avoid
    introducing circular locking dependency through printk but not effective
    as it still had pool lock -> wci_lock -> printk -> pool lock loop. Let's
    just print directly using printk_deferred().

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>

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This commit is contained in:

Tejun Heo 2023-05-17 17:02:08 -10:00

parent 616db8779b

commit 6363845005

3 changed files with 111 additions and 0 deletions

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kernel/workqueue.c

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