3.2.93-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> commit 63aea0dbab90a2461faaae357cbc8cfd6c8de9fe upstream. With threaded interrupts, bottom-half handlers are called with interrupts enabled. Therefore they can't safely use spin_lock(); they have to use spin_lock_irqsave(). Lockdep warns about a violation occurring in xhci_irq(): ========================================================= [ INFO: possible irq lock inversion dependency detected ] 4.11.0-rc8-dbg+ #1 Not tainted --------------------------------------------------------- swapper/7/0 just changed the state of lock: (&(&ehci->lock)->rlock){-.-...}, at: [<ffffffffa0130a69>] ehci_hrtimer_func+0x29/0xc0 [ehci_hcd] but this lock took another, HARDIRQ-unsafe lock in the past: (hcd_urb_list_lock){+.....} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(hcd_urb_list_lock); local_irq_disable(); lock(&(&ehci->lock)->rlock); lock(hcd_urb_list_lock); <Interrupt> lock(&(&ehci->lock)->rlock); *** DEADLOCK *** no locks held by swapper/7/0. the shortest dependencies between 2nd lock and 1st lock: -> (hcd_urb_list_lock){+.....} ops: 252 { HARDIRQ-ON-W at: __lock_acquire+0x602/0x1280 lock_acquire+0xd5/0x1c0 _raw_spin_lock+0x2f/0x40 usb_hcd_unlink_urb_from_ep+0x1b/0x60 [usbcore] xhci_giveback_urb_in_irq.isra.45+0x70/0x1b0 [xhci_hcd] finish_td.constprop.60+0x1d8/0x2e0 [xhci_hcd] xhci_irq+0xdd6/0x1fa0 [xhci_hcd] usb_hcd_irq+0x26/0x40 [usbcore] irq_forced_thread_fn+0x2f/0x70 irq_thread+0x149/0x1d0 kthread+0x113/0x150 ret_from_fork+0x2e/0x40 This patch fixes the problem. Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Reported-and-tested-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- drivers/usb/host/xhci-ring.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -2645,11 +2645,12 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd union xhci_trb *trb; union xhci_trb *event_ring_deq; irqreturn_t ret = IRQ_NONE; + unsigned long flags; dma_addr_t deq; u64 temp_64; u32 status; - spin_lock(&xhci->lock); + spin_lock_irqsave(&xhci->lock, flags); trb = xhci->event_ring->dequeue; /* Check if the xHC generated the interrupt, or the irq is shared */ status = xhci_readl(xhci, &xhci->op_regs->status); @@ -2724,7 +2725,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd ret = IRQ_HANDLED; out: - spin_unlock(&xhci->lock); + spin_unlock_irqrestore(&xhci->lock, flags); return ret; }