Re: [PATCH v3 1/3] workqueue: Provide a handshake for canceling BH workers

[Tejun Heo <tj@kernel.org>]

On Thu, Sep 04, 2025 at 04:25:23PM +0200, Sebastian Andrzej Siewior wrote:
> While a BH work item is canceled, the core code spins until it
> determines that the item completed. On PREEMPT_RT the spinning relies on
> a lock in local_bh_disable() to avoid a live lock if the canceling
> thread has higher priority than the BH-worker and preempts it. This lock
> ensures that the BH-worker makes progress by PI-boosting it.
> 
> This lock in local_bh_disable() is a central per-CPU BKL and about to be
> removed.
> 
> To provide the required synchronisation add a per pool lock. The lock is
> acquired by the bh_worker at the begin while the individual callbacks
> are invoked. To enforce progress in case of interruption, __flush_work()
> needs to acquire the lock.
> This will flush all BH-work items assigned to that pool.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Applied to wq/for-6.18.

Thanks.

-- 
tejun