Re: BUG due to "xen-netback: protect resource cleaning on XenBus disconnect"

-----Original Message-----
From: Juergen Gross [mailto:jgross@suse.com]
Sent: 02 March 2017 12:13
To: Wei Liu <redacted>
Cc: Igor Druzhinin <redacted>; xen-devel <xen-
devel@lists.xenproject.org>; Linux Kernel Mailing List <linux-
kernel@vger.kernel.org>; netdev@vger.kernel.org; Boris Ostrovsky
[off-list ref]; David Miller [off-list ref]; Paul
Durrant [off-list ref]
Subject: Re: BUG due to "xen-netback: protect resource cleaning on XenBus
disconnect"

On 02/03/17 13:06, Wei Liu wrote:

quoted

On Thu, Mar 02, 2017 at 12:56:20PM +0100, Juergen Gross wrote:

quoted

With commits f16f1df65 and 9a6cdf52b we get in our Xen testing:

[  174.512861] switch: port 2(vif3.0) entered disabled state
[  174.522735] BUG: sleeping function called from invalid context at
/home/build/linux-linus/mm/vmalloc.c:1441
[  174.523451] in_atomic(): 1, irqs_disabled(): 0, pid: 28, name: xenwatch
[  174.524131] CPU: 1 PID: 28 Comm: xenwatch Tainted: G        W
4.10.0upstream-11073-g4977ab6-dirty #1
[  174.524819] Hardware name: MSI MS-7680/H61M-P23 (MS-7680), BIOS

V17.0

quoted

quoted

03/14/2011
[  174.525517] Call Trace:
[  174.526217]  show_stack+0x23/0x60
[  174.526899]  dump_stack+0x5b/0x88
[  174.527562]  ___might_sleep+0xde/0x130
[  174.528208]  __might_sleep+0x35/0xa0
[  174.528840]  ? _raw_spin_unlock_irqrestore+0x13/0x20
[  174.529463]  ? __wake_up+0x40/0x50
[  174.530089]  remove_vm_area+0x20/0x90
[  174.530724]  __vunmap+0x1d/0xc0
[  174.531346]  ? delete_object_full+0x13/0x20
[  174.531973]  vfree+0x40/0x80
[  174.532594]  set_backend_state+0x18a/0xa90
[  174.533221]  ? dwc_scan_descriptors+0x24d/0x430
[  174.533850]  ? kfree+0x5b/0xc0
[  174.534476]  ? xenbus_read+0x3d/0x50
[  174.535101]  ? xenbus_read+0x3d/0x50
[  174.535718]  ? xenbus_gather+0x31/0x90
[  174.536332]  ? ___might_sleep+0xf6/0x130
[  174.536945]  frontend_changed+0x6b/0xd0
[  174.537565]  xenbus_otherend_changed+0x7d/0x80
[  174.538185]  frontend_changed+0x12/0x20
[  174.538803]  xenwatch_thread+0x74/0x110
[  174.539417]  ? woken_wake_function+0x20/0x20
[  174.540049]  kthread+0xe5/0x120
[  174.540663]  ? xenbus_printf+0x50/0x50
[  174.541278]  ? __kthread_init_worker+0x40/0x40
[  174.541898]  ret_from_fork+0x21/0x2c
[  174.548635] switch: port 2(vif3.0) entered disabled state

I believe calling vfree() when holding a spin_lock isn't a good idea.

Use vfree_atomic instead?

Hmm, isn't this overkill here?

You can just set a local variable with the address and do vfree() after
releasing the lock.

Yep, that's what I was thinking. Patch coming shortly.

  Paul

Juergen

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