Re: [PATCH net-next v2 2/2] net: wwan: qcom_bam_dmux: Assign restricted DMA pool to remote processor

[Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>]

> If probe fails late (for example, if irq_get_irqchip_state() returns an
> error), the code jumps to the err_disable_pm label. At this point, the
> pc_irq has already been requested via devm_request_threaded_irq() and
> is active.
>
> If the remote processor triggers this interrupt, the threaded handler
> (bam_dmux_pc_irq) could be executing bam_dmux_power_on() while we are
> calling bam_dmux_reclaim_dma_pool().
>
> This concurrent execution would cause the DMA pool to be reclaimed
> while the BAM DMA controller is actively using it, resulting in a system
> crash. Furthermore, when devres eventually frees the IRQ, any DMA
> channels or mappings allocated by the racing handler would leak because
> bam_dmux_power_off() is not called in this error path.

Agreed, the late error path should tear down everything the PC IRQ may
already have set up. I plan to reuse bam_dmux_remove() for this, which
disables the IRQ and releases the DMA channels, mappings and any
registered netdevs before reclaiming the pool, in the same order as a
regular remove. I will test this and include it in the next revision.

Thanks,
Vishnu