The interrupt service routine registered for the gadget is a primary handler which mask the interrupt source and a threaded handler which handles the source of the interrupt. Since the threaded handler is voluntary threaded, the IRQ-core does not disable bottom halves before invoke the handler like it does for the forced-threaded handler. Due to changes in networking it became visible that a network gadget's completions handler may schedule a softirq which remains unprocessed. The gadget's completion handler is usually invoked either in hard-IRQ or soft-IRQ context. In this context it is enough to just raise the softirq because the softirq itself will be handled once that context is left. In the case of the voluntary threaded handler, there is nothing that will process pending softirqs. Which means it remain queued until another random interrupt (on this CPU) fires and handles it on its exit path or another thread locks and unlocks a lock with the bh suffix. Worst case is that the CPU goes idle and the NOHZ complains about unhandled softirqs. Disable bottom halves before acquiring the lock (and disabling interrupts) and enable them after dropping the lock. This ensures that any pending softirqs will handled right away. Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Link: https://lkml.kernel.org/r/c2a64979-73d1-2c22-e048-c275c9f81558@xxxxxxxxxxx Fixes: e5f68b4a3e7b0 ("Revert "usb: dwc3: gadget: remove unnecessary _irqsave()"") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> --- drivers/usb/dwc3/gadget.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 183b90923f51b..a0c883f19a417 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -4160,9 +4160,11 @@ static irqreturn_t dwc3_thread_interrupt(int irq, void *_evt) unsigned long flags; irqreturn_t ret = IRQ_NONE; + local_bh_disable(); spin_lock_irqsave(&dwc->lock, flags); ret = dwc3_process_event_buf(evt); spin_unlock_irqrestore(&dwc->lock, flags); + local_bh_enable(); return ret; } -- 2.34.1
