On 02.05.2017 17:34, Alan Stern wrote:
On Tue, 2 May 2017, Mathias Nyman wrote:
On 01.05.2017 22:41, Alan Stern wrote:
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>
CC: <stable@xxxxxxxxxxxxxxx>
Acked-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Mathias, will you take this patch or should I send it to Greg?
I can take it and send it forward to Greg after rc1
-Mathias
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