This is a note to let you know that I've just added the patch titled
usb: ehci: fix deadlock when threadirqs option is used
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-ehci-fix-deadlock-when-threadirqs-option-is-used.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a1227f3c1030e96ebc51d677d2f636268845c5fb Mon Sep 17 00:00:00 2001
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Date: Wed, 19 Feb 2014 10:29:01 +0100
Subject: usb: ehci: fix deadlock when threadirqs option is used
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
commit a1227f3c1030e96ebc51d677d2f636268845c5fb upstream.
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>
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ehci-hcd.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -686,8 +686,15 @@ static irqreturn_t ehci_irq (struct usb_
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);
@@ -705,7 +712,7 @@ static irqreturn_t ehci_irq (struct usb_
/* 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;
}
@@ -823,7 +830,7 @@ 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;
Patches currently in stable-queue which might be from sgruszka@xxxxxxxxxx are
queue-3.13/usb-ehci-fix-deadlock-when-threadirqs-option-is-used.patch
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