Re: WARNING: at kernel/resource.c:189 __release_resource

[Bjorn Helgaas]

On Monday 26 November 2007 11:05:38 pm Andrew Morton wrote:
> On Thu, 22 Nov 2007 22:41:16 +0100 Jiri Slaby <jirislaby@xxxxxxxxx> wrote:
> > Ok, I hit the bug, suspend of 00:06 device complains about it:
> > WARNING: at .../kernel/resource.c:185 __release_resource()
> > 
> > Call Trace:
> >  [<ffffffff8023f7b5>] release_resource+0xb5/0xf0
> >  [<ffffffff8036cda0>] pnp_release_resources+0x70/0x130
> >  [<ffffffff8036db85>] pnp_stop_dev+0x45/0x90
> >  [<ffffffff8036c942>] pnp_bus_suspend+0x92/0xb0
> >  [<ffffffff803b9f73>] suspend_device+0x113/0x180
> >  [<ffffffff803ba330>] device_suspend+0x200/0x320
> >  [<ffffffff80266905>] suspend_devices_and_enter+0xa5/0x170
> >  [<ffffffff80266bd9>] enter_state+0x209/0x270
> >  [<ffffffff80266cef>] state_store+0xaf/0xf0
> >  [<ffffffff8032ca67>] kobj_attr_store+0x17/0x20
> >  [<ffffffff802e459e>] sysfs_write_file+0xce/0x140
> >  [<ffffffff80299cc7>] vfs_write+0xc7/0x170
> >  [<ffffffff8029a360>] sys_write+0x50/0x90
> >  [<ffffffff8020bcde>] system_call+0x7e/0x83
> > 
> > # LANG=en ll /sys/devices/pnp0/00:06/
> > total 0
> > lrwxrwxrwx 1 root root    0 Nov 22 22:35 driver -> ../../../bus/pnp/drivers/serial
> > -r--r--r-- 1 root root 4096 Nov 22 22:35 id
> > -r--r--r-- 1 root root 4096 Nov 22 22:35 options
> > drwxr-xr-x 2 root root    0 Nov 22 22:35 power
> > -rw-r--r-- 1 root root 4096 Nov 22 22:35 resources
> > lrwxrwxrwx 1 root root    0 Nov 22 22:35 subsystem -> ../../../bus/pnp
> > drwxr-xr-x 3 root root    0 Nov 22 22:35 tty
> > -rw-r--r-- 1 root root 4096 Nov 22 22:35 uevent
> 
> I suppose that's a genuine leak, presumably in 8250_pnp.

We used to have only the serial driver resource reservation.  We now
have an additional 00:06 resource that is the parent of the serial
resource, e.g.,

  03f8-03ff : 00:06
    03f8-03ff : serial

I think this problem happens because pnp_bus_suspend() calls
serial_pnp_suspend(), which suspends the driver but does nothing
with the resources.  Then it calls pnp_stop_dev(), which releases
the 00:06 resource, which still has a serial child resource.

The corresponding PCI code in pci_device_suspend() does not do
any generic device disable or resource release.  I don't know
why PNP disables the device on suspend.  I glanced through the
ACPI spec but didn't see a requirement for it.  Maybe Pierre [1]
remembers.

Maybe we could either remove the pnp_{stop,start}_dev() calls
from the suspend/resume path, or move the PNP resource management
out of pnp_{start,stop}_dev().

Bjorn

[1] http://lkml.org/lkml/2005/11/30/39
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