Re: [PATCH 6/6] backlight: qcom-wled: Avoid AB-BA deadlock in wled_module_enable()

[Konrad Dybcio]

On 11/4/26 7:39 PM, Lee Jones wrote:
> When disabling the WLED module (for example from wled_update_status() or
> wled_short_irq_handler()), the caller holds wled->lock and invokes
> wled_module_enable(wled, false), which calls disable_irq(wled->ovp_irq)
> and blocks waiting for any executing OVP threaded interrupt handler to
> complete.
> 
> If wled_ovp_irq_handler() is concurrently executing, it attempts to
> acquire wled->lock before running wled_auto_string_detection(),
> resulting in an AB-BA deadlock between wled->lock and IRQ completion.
> 
> Use disable_irq_nosync() instead of disable_irq() in
> wled_module_enable() so that the OVP interrupt is masked without
> synchronously waiting for the threaded handler while holding wled->lock.
> Because wled_ovp_irq_handler() may already be waiting on wled->lock when
> the module is disabled, verify under wled->lock that the module is still
> enabled and not disabled by a short before running
> wled_auto_string_detection().
> 
> Fixes: 8663c188beea ("backlight: qcom-wled: Add auto string detection logic")
> Closes: https://sashiko.dev/#/bug/linux-3afa151c-7b8f-432c-8f85-8c43a83b964a
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
> ---

Acked-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>

Konrad