This is a note to let you know that I've just added the patch titled
USB: xhci: fix lock-inversion problem
to the 4.11-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-xhci-fix-lock-inversion-problem.patch
and it can be found in the queue-4.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 63aea0dbab90a2461faaae357cbc8cfd6c8de9fe Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 17 May 2017 18:32:03 +0300
Subject: USB: xhci: fix lock-inversion problem
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>
---
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
@@ -2616,11 +2616,12 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd
struct xhci_hcd *xhci = hcd_to_xhci(hcd);
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);
/* Check if the xHC generated the interrupt, or the irq is shared */
status = readl(&xhci->op_regs->status);
if (status == 0xffffffff) {
@@ -2695,7 +2696,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd
ret = IRQ_HANDLED;
out:
- spin_unlock(&xhci->lock);
+ spin_unlock_irqrestore(&xhci->lock, flags);
return ret;
}
Patches currently in stable-queue which might be from stern@xxxxxxxxxxxxxxxxxxx are
queue-4.11/ohci-pci-add-qemu-quirk.patch
queue-4.11/usb-ene_usb6250-fix-dma-to-the-stack.patch
queue-4.11/usb-xhci-fix-lock-inversion-problem.patch