[PATCH v2] genirq/kexec: Do not take the bus lock of an interrupt chip on the crash path

[sashiko-bot at kernel.org]

> From: Igor Velkov <iav at iav.lv>
> 
> machine_kexec_mask_interrupts() calls irq_set_irqchip_state() for every
> started interrupt. That function takes the bus lock of the chip and
> desc->lock, and syncs the chip when it drops them. On the crash path
> interrupts are off and the other CPUs are stopped, so a chip whose bus
> transfer is completed by an interrupt never returns from the sync.
> 
> On RK3399 boards with an RK808 PMIC the RTC alarm interrupt belongs to
> the regmap-irq chip of the RK808, which sits on I2C. rk808_irq_chip sets
> init_ack_masked, so regmap_irq_sync_unlock() writes the ack register on
> every unlock, and the I2C controller needs its own interrupt to finish
> the transfer. A panic with a crash kernel loaded prints
> 
>   SMP: stopping secondary CPUs
> 
> and then nothing until the watchdog resets the board.
> 
> machine_kexec_mask_interrupts() takes neither lock for the other
> operations on the descriptor. Move the search for the chip that
> implements irq_set_irqchip_state() into __irq_set_irqchip_state(), which
> takes no locks, and call it from machine_kexec_mask_interrupts().
> 
> Fixes: 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
> Suggested-by: Thomas Gleixner <tglx at kernel.org>
> Assisted-by: LLM
> Signed-off-by: Igor Velkov <iav at iav.lv>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261015-kexec-irq-bus-lock-v2-1-2af15f0757b6@iav.lv?part=1