Re: Linux 4.2-rc5:

[Ross Lagerwall <ross.lagerwall@citrix.com>]

On 08/06/2015 08:51 PM, linux@eikelenboom.it wrote:
> Hi Ross,
>
> On my dom0 with a linux 4.2-rc5 kernel i encoutered the splat below.
> It's probably related to your patch that went in just for 4.2-rc5:
> "xen/events/fifo: Handle linked events when closing a port"
>
> --
> Sander
>
> [   49.020173] ------------[ cut here ]------------
> [   49.020187] WARNING: CPU: 0 PID: 1 at
> drivers/xen/events/events_fifo.c:395 evtchn_fifo_close+0xbd/0xc0()
> [   49.020191] Modules linked in:
> [   49.020198] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> 4.2.0-rc5-20150804-linus-doflr+ #1
> [   49.020200] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS
> V1.8B1 09/13/2010
> [   49.020208]  ffffffff81faaae8 ffff880059b9bad8 ffffffff81aed513
> 0000000000000000
> [   49.020214]  0000000000000000 ffff880059b9bb18 ffffffff810c7280
> 0000000000000041
> [   49.020219]  0000000000000041 0000000000000000 ffff880059807ca8
> ffff880059807c00
> [   49.020220] Call Trace:
> [   49.020233]  [<ffffffff81aed513>] dump_stack+0x45/0x57
> [   49.020240]  [<ffffffff810c7280>] warn_slowpath_common+0x80/0xc0
> [   49.020245]  [<ffffffff810c7365>] warn_slowpath_null+0x15/0x20
> [   49.020249]  [<ffffffff814f1b9d>] evtchn_fifo_close+0xbd/0xc0
> [   49.020278]  [<ffffffff814eeabd>] xen_evtchn_close+0x1d/0x60
> [   49.020281]  [<ffffffff811055f9>] ? irq_get_irq_data+0x9/0x20
> [   49.020282]  [<ffffffff814ef9eb>] shutdown_pirq+0x4b/0x70
> [   49.020283]  [<ffffffff81105be4>] irq_shutdown+0x34/0x70
> [   49.020285]  [<ffffffff811034ed>] __free_irq+0x19d/0x1e0
> [   49.020286]  [<ffffffff811035b8>] free_irq+0x48/0xb0
> [   49.020287]  [<ffffffff8234f3ec>] i8042_probe+0x38f/0x693
> [   49.020291]  [<ffffffff816800cf>] platform_drv_probe+0x2f/0x90
> [   49.020292]  [<ffffffff8167e3ff>] driver_probe_device+0x1af/0x2d0
> [   49.020293]  [<ffffffff8167e5ab>] __driver_attach+0x8b/0x90
> [   49.020294]  [<ffffffff8167e520>] ? driver_probe_device+0x2d0/0x2d0
> [   49.020296]  [<ffffffff8167c5bf>] bus_for_each_dev+0x5f/0x90
> [   49.020297]  [<ffffffff8167df09>] driver_attach+0x19/0x20
> [   49.020298]  [<ffffffff8167db5b>] bus_add_driver+0x1ab/0x220
> [   49.020299]  [<ffffffff8167ee0b>] driver_register+0x5b/0xe0
> [   49.020300]  [<ffffffff81680035>] __platform_driver_register+0x45/0x50
> [   49.020301]  [<ffffffff81680241>] __platform_driver_probe+0x31/0xe0
> [   49.020303]  [<ffffffff81680663>] __platform_create_bundle+0xa3/0xd0
> [   49.020304]  [<ffffffff8234f05d>] ? i8042_toggle_aux+0x6c/0x6c
> [   49.020305]  [<ffffffff8234f6f0>] ? i8042_probe+0x693/0x693
> [   49.020306]  [<ffffffff8234fac0>] i8042_init+0x3d0/0x3f6
> [   49.020308]  [<ffffffff810020f7>] do_one_initcall+0x87/0x1d0
> [   49.020310]  [<ffffffff82313147>] kernel_init_freeable+0x1db/0x263
> [   49.020312]  [<ffffffff81ae7610>] ? rest_init+0x80/0x80
> [   49.020314]  [<ffffffff81ae7619>] kernel_init+0x9/0xe0
> [   49.020315]  [<ffffffff81af7d1f>] ret_from_fork+0x3f/0x70
> [   49.020317]  [<ffffffff81ae7610>] ? rest_init+0x80/0x80
> [   49.020320] ---[ end trace 64c385518fcbbfa1 ]---
>

Thanks.

This means that the event channel is being closed with interrupts 
disabled, so it cannot guarantee that the event is not linked in. This 
is not a regression in behavior -- previously this was _never_ 
guaranteed and just silently ignored. However, we should find a way to 
fix this completely, to avoid warning spam.

Regards,
-- 
Ross Lagerwall