5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ralph Siemsen ralph.siemsen@linaro.org
commit a1059896f2bfdcebcdc7153c3be2307ea319501f upstream.
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 stable@kernel.org Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver") Signed-off-by: Ralph Siemsen ralph.siemsen@linaro.org Acked-by: Peter Chen peter.chen@kernel.org Reviewed-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Link: https://lore.kernel.org/r/20250318-rfs-cdns3-deadlock-v2-1-bfd9cfcee732@lina... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/cdns3/gadget.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/usb/cdns3/gadget.c +++ b/drivers/usb/cdns3/gadget.c @@ -1920,6 +1920,7 @@ static int cdns3_gadget_ep_disable(struc "%s is already disabled\n", priv_ep->name)) return 0;
+ local_bh_disable(); spin_lock_irqsave(&priv_dev->lock, flags);
trace_cdns3_gadget_ep_disable(priv_ep); @@ -1976,6 +1977,7 @@ static int cdns3_gadget_ep_disable(struc priv_ep->flags &= ~EP_ENABLED;
spin_unlock_irqrestore(&priv_dev->lock, flags); + local_bh_enable();
return ret; }