Re: [PATCH ath-next] wifi: ath11k: cancel SSR work items during PCI shutdown

[Rameshkumar Sundaram]

On 4/4/2026 10:00 AM, Wei Zhang wrote:
> A reboot can crash the kernel if it overlaps with WLAN firmware crash
> recovery (SSR). The crash is a NULL pointer dereference in the MHI teardown
> path while freeing DMA-backed MHI contexts.
>
> Simplified trace:
>    dma_free_attrs
>    mhi_deinit_dev_ctxt [mhi]
>    ath11k_pci_power_down [ath11k_pci]
>    ath11k_pci_shutdown [ath11k_pci]
>    device_shutdown
>    kernel_restart
>
> On the host side, SSR is driven by the MHI RDDM callback, which queues
> reset_work to perform device recovery. reset_work power-cycles the device
> by calling ath11k_hif_power_down() followed by ath11k_hif_power_up(). The
> power-down phase deinitializes MHI and frees DMA resources.
>
> Shutdown/reboot runs fully asynchronously with this RDDM-driven SSR
> recovery flow. As a result, the shutdown path
> (ath11k_pci_shutdown() -> ath11k_pci_power_down()) can race with the SSR
> recovery sequence.
>
> Fix this by canceling SSR-related work items during PCI shutdown, marking
> the device as unregistering, and serializing the RDDM callback path that
> checks and queues reset_work. This ensures that no new SSR recovery work
> can be queued once teardown has started, and that any in-flight recovery
> work is fully synchronized before device power-down, preventing MHI
> teardown and DMA resource freeing from running more than once.
>
> Note: This issue only affects PCI/MHI-based devices. AHB-based ath11k
> devices do not queue reset_work in normal SSR flows.
>
> Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-04866.5-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1
>
> Fixes: 13da397f884d ("ath11k: add support for device recovery for QCA6390/WCN6855")
> Fixes: 5edbb148bc57 ("wifi: ath11k: Add firmware coredump collection support")
> Signed-off-by: Wei Zhang <wei.zhang@xxxxxxxxxxxxxxxx>
Reviewed-by: Rameshkumar Sundaram <rameshkumar.sundaram@xxxxxxxxxxxxxxxx>