Re: [PATCH v2] ASoC: meson: axg-fifo: fix irq scheduling issue with PREEMPT_RT

[Sebastian Andrzej Siewior]

On 2024-08-07 18:27:03 [+0200], Jerome Brunet wrote:
> With PREEMPT_RT enabled a spinlock_t becomes a sleeping lock.
> 
> This is usually not a problem with spinlocks used in IRQ context since
> IRQ handlers get threaded. However, if IRQF_ONESHOT is set, the primary
> handler won't be force-threaded and runs always in hardirq context. This is
> a problem because spinlock_t requires a preemptible context on PREEMPT_RT.
> 
> In this particular instance, regmap mmio uses spinlock_t to protect the
> register access and IRQF_ONESHOT is set on the IRQ. In this case, it is
> actually better to do everything in threaded handler and it solves the
> problem with PREEMPT_RT.
> 
> Reported-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-amlogic/20240729131652.3012327-1-avkrasnov@xxxxxxxxxxxxxxxxx
> Suggested-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Fixes: b11d26660dff ("ASoC: meson: axg-fifo: use threaded irq to check periods")
> Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Sebastian