linux-kernel - Re: [PATCH PREEMPT_RT] i915: fix PREEMPT

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Date:   Wed, 8 Sep 2021 21:05:12 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Clark Williams <williams@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Airlie <airlied@...ux.ie>,
        LKML <linux-kernel@...r.kernel.org>,
        RT <linux-rt-users@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH PREEMPT_RT] i915: fix PREEMPT_RT locking splats

On 2021-08-23 15:00:15 [-0500], Clark Williams wrote:
> Found two separate spots where i915 was throwing "sleeping
> function called from invalid context" when running on a
> PREEMPT_RT kernel. In both cases it was from calling
> local_irq_disable prior to taking a spin_lock. Since spin
> locks are converted to rt_mutex_t on PREEMPT_RT this means
> that we might sleep with interrupts disabled.
> 
> Since in both cases the calls were in threaded context on RT
> (irq or ksoftirqd) and in no danger of reentrance, change the
> code to only disable interrupts on non-PREEMPT_RT kernels.
> 
> Signed-off-by: Clark Williams <williams@...hat.com>

I try to deal with this in
   https://lkml.kernel.org/r/20210908185703.2989414-1-bigeasy@linutronix.de

Sebastian