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>

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 4711427..81cda09 100644 (file)
--- 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;