[Xen-devel] Re: xenstored unsafe lock order detected, xlate_proc_name, evtchn_ioctl, port_user_lock

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 06/06/2010 10:33 AM, Pasi Kärkkäinen wrote:
> Hello,
>
> I just tried the latest xen/stable-2.6.32.x kernel, ie. 2.6.32.15, with Xen 
> 4.0.0,
> and I got this:
>
> http://pasik.reaktio.net/xen/pv_ops-dom0-debug/log-2.6.32.15-pvops-dom0-xen-stable-x86_64.txt
>   

Does this help?

>From 3f5e554f669098c84c82ce75e7577f7e0f3fccde Mon Sep 17 00:00:00 2001
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Date: Fri, 28 May 2010 15:28:27 -0700
Subject: [PATCH] xen/evtchn: don't do unbind_from_irqhandler under spinlock

unbind_from_irqhandler can end up doing /proc operations, which can't
happen under a spinlock.  So before removing the IRQ handler,
disable the irq under the port_user lock (masking the underlying event
channel and making sure the irq handler isn't running concurrently and
won't start running), then remove the handler without the lock.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index f79ac5c..6a3a129 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -375,10 +375,12 @@ static long evtchn_ioctl(struct file *file,
                        break;
                }
 
-               evtchn_unbind_from_user(u, unbind.port);
+               disable_irq(irq_from_evtchn(unbind.port));
 
                spin_unlock_irq(&port_user_lock);
 
+               evtchn_unbind_from_user(u, unbind.port);
+
                rc = 0;
                break;
        }
@@ -484,11 +486,18 @@ static int evtchn_release(struct inode *inode, struct 
file *filp)
                if (get_port_user(i) != u)
                        continue;
 
-               evtchn_unbind_from_user(get_port_user(i), i);
+               disable_irq(irq_from_evtchn(i));
        }
 
        spin_unlock_irq(&port_user_lock);
 
+       for (i = 0; i < NR_EVENT_CHANNELS; i++) {
+               if (get_port_user(i) != u)
+                       continue;
+
+               evtchn_unbind_from_user(get_port_user(i), i);
+       }
+
        kfree(u->name);
        kfree(u);
 



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