Re: [PATCH v4 7/7] drm/i915/gt: Use signalers_lock to prevent starvation of irq_work.

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2026-07-06 13:48:23 [+0200], Maarten Lankhorst wrote:
> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> 
> IRQ-Work (FIFO-1) will be preempted by the threaded-interrupt (FIFO-50)
> and the interrupt will poll on signaler_active while the irq-work can't
> make progress.
> 
> Solve this by adding a global spinlock to prevent starvation and force
> completion.
> 
> The existing RCU handling gets in the way on PREEMPT_RT, and would likely
> require conversion to raw spinlock to take them inside a
> rcu_read_lock(), so remove RCU as well.

You require both locks and a try-lock since the ordering is wrong. And
you replace the RCU-section with a lock. Understood.

You probably want to make yourself as the author and make me
Co-developed-by or something or nothing. This would fix the Sob order
below.

> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

Sebastian