usb: ehci: fix deadlock when threadirqs option is used

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@redhat.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 471142725ffe..81cda09b47e3 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;