On Wed, 19 Feb 2014, Stanislaw Gruszka wrote:
> ehci_irq() and ehci_hrtimer_func() can deadlock on ehci->lock when
> threadirqs option is used. To prevent the deadlock use
> spin_lock_irqsave() in ehci_irq().
>
> This change can be reverted when hrtimer callbacks become threaded.
>
> Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
> ---
> drivers/usb/host/ehci-hcd.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
> index 4711427..0bc6410 100644
> --- a/drivers/usb/host/ehci-hcd.c
> +++ b/drivers/usb/host/ehci-hcd.c
> @@ -685,8 +685,15 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
> struct ehci_hcd *ehci = hcd_to_ehci (hcd);
> u32 status, masked_status, pcd_status = 0, cmd;
> int bh;
> + unsigned long flags;
>
> - spin_lock (&ehci->lock);
> + /*
> + * For threadirqs option we use spin_lock_irqsave() variant to prevent
> + * deadlock with ehci hrtimer callback, because hrtimer callbacks run
> + * in interrupt context even when threadirqs is specified. We can go
> + * back to spin_lock() variant when hrtimer callbacks become threaded.
> + */
> + spin_lock_irqsave(&ehci->lock, flags);
>
> status = ehci_readl(ehci, &ehci->regs->status);
>
> @@ -704,7 +711,7 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
>
> /* Shared IRQ? */
> if (!masked_status || unlikely(ehci->rh_state == EHCI_RH_HALTED)) {
> - spin_unlock(&ehci->lock);
> + spin_unlock_irqrestore(&ehci->lock, flags);
> return IRQ_NONE;
> }
>
> @@ -815,7 +822,7 @@ dead:
>
> if (bh)
> ehci_work (ehci);
> - spin_unlock (&ehci->lock);
> + spin_unlock_irqrestore(&ehci->lock, flags);
> if (pcd_status)
> usb_hcd_poll_rh_status(hcd);
> return IRQ_HANDLED;
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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