Re: [PATCH v2] usb: cdns3: Fix deadlock when using NCM gadget

On 2025-03-18 11:09:32 [-0400], Ralph Siemsen wrote:

The cdns3 driver has the same NCM deadlock as fixed in cdnsp by commit 58f2fcb3a845 ("usb: cdnsp: Fix deadlock issue during using NCM gadget").

Under PREEMPT_RT the deadlock can be readily triggered by heavy network traffic, for example using "iperf --bidir" over NCM ethernet link.

The deadlock occurs because the threaded interrupt handler gets preempted by a softirq, but both are protected by the same spinlock. Prevent deadlock by disabling softirq during threaded irq handler.

cc: stable@vger.kernel.org Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver") Signed-off-by: Ralph Siemsen ralph.siemsen@linaro.org

Reviewed-by: Sebastian Andrzej Siewior bigeasy@linutronix.de

Sebastian