kernel: sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists

kernel: sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists

[Dave Jones]

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Well, that's umm, special.
I wonder if powering off the printer isn't causing the sysctl to be removed,
causing the next power-on to look like a new device ?
Eric, you poked around the sysctl paths in parport last year, any ideas?

	Dave

-- 
http://www.codemonkey.org.uk

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From: bugzilla@redhat.com
To: kernel-maint@redhat.com
Subject: [Bug 449112] New: kernel:<3>sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists
Date: Fri, 30 May 2008 10:15:51 -0400
Message-ID: <bug-449112-176318@bugzilla.redhat.com>

Please do not reply directly to this email. All additional
comments should be made in the comments box of this bug report.




https://bugzilla.redhat.com/show_bug.cgi?id=449112

           Summary: kernel:<3>sysctl table check failed:
                    /dev/parport/parport0/devices/ppdev0/timeslice  Sysctl
                    already exists
           Product: Fedora
           Version: rawhide
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: low
          Priority: low
         Component: kernel
        AssignedTo: kernel-maint@redhat.com
        ReportedBy: selinux@gmail.com
         QAContact: extras-qa@fedoraproject.org


Description of problem:
Get the following in dmesg. I had "printed" to an HP5MP printer from firefox,
but the printer was powered off.  I turned on the printer, and I believe got these.

ppdev0: registered pardevice
sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice 
Sysctl already exists
Pid: 3921, comm: hp Not tainted 2.6.26-0.44.rc4.git2.fc10.i686 #1
 [<c04407ae>] set_fail+0x33/0x40
 [<c0440bc4>] sysctl_check_table+0x409/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c043148c>] __register_sysctl_paths+0xa7/0xf9
 [<c04314fc>] register_sysctl_paths+0x1e/0x20
 [<c043150d>] register_sysctl_table+0xf/0x11
 [<f8db831f>] parport_device_proc_register+0xa9/0xc7 [parport]
 [<f8db6b2c>] parport_register_device+0x1c1/0x1eb [parport]
 [<f8dfe328>] pp_ioctl+0x12e/0x6b2 [ppdev]
 [<f8dfe8ac>] ? pp_irq+0x0/0x43 [ppdev]
 [<c04982ac>] vfs_ioctl+0x50/0x69
 [<c04984fe>] do_vfs_ioctl+0x239/0x24c
 [<c04df7dc>] ? selinux_file_ioctl+0x35/0x38
 [<c0498551>] sys_ioctl+0x40/0x5b
 [<c0404c3a>] syscall_call+0x7/0xb
 =======================
ppdev0: registered pardevice
sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice 
Sysctl already exists
Pid: 3921, comm: hp Not tainted 2.6.26-0.44.rc4.git2.fc10.i686 #1
 [<c04407ae>] set_fail+0x33/0x40
 [<c0440bc4>] sysctl_check_table+0x409/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c0440bda>] sysctl_check_table+0x41f/0x445
 [<c043148c>] __register_sysctl_paths+0xa7/0xf9
 [<c04314fc>] register_sysctl_paths+0x1e/0x20
 [<c043150d>] register_sysctl_table+0xf/0x11
 [<f8db831f>] parport_device_proc_register+0xa9/0xc7 [parport]
 [<f8db6b2c>] parport_register_device+0x1c1/0x1eb [parport]
 [<f8dfe328>] pp_ioctl+0x12e/0x6b2 [ppdev]
 [<f8dfe8ac>] ? pp_irq+0x0/0x43 [ppdev]
 [<c04982ac>] vfs_ioctl+0x50/0x69
 [<c04984fe>] do_vfs_ioctl+0x239/0x24c
 [<c04df7dc>] ? selinux_file_ioctl+0x35/0x38
 [<c0498551>] sys_ioctl+0x40/0x5b
 [<c0404c3a>] syscall_call+0x7/0xb
 =======================
ppdev0: registered pardevice
ppdev0: unregistered pardevice
ppdev0: unregistered pardevice
ppdev0: unregistered pardevice


Version-Release number of selected component (if applicable):
kernel-2.6.26-0.44.rc4.git2.fc10.i686

How reproducible:
Don't know....

Steps to Reproduce:
1.
2.
3.
  
Actual results:


Expected results:


Additional info:

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Re: kernel: sysctl table check failed: /dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists

[Eric W. Biederman]

Dave Jones <davej@redhat.com> writes:

> Well, that's umm, special.
> I wonder if powering off the printer isn't causing the sysctl to be removed,
> causing the next power-on to look like a new device ?
> Eric, you poked around the sysctl paths in parport last year, any ideas?

Yes.  The short answer is that this is a real bug in the parport code
that has existed forever.  We just now complain.

http://bugzilla.kernel.org/show_bug.cgi?id=9749

It takes something like two accessors of the parallel port to trigger
this.  Though not in a bad way.

In particular each open creates the sysctl for the duration of the
open (or something like that) and so if you open (I think it is
/dev/parport0) twice you try and create the sysctls twice.

I got as far as basic confirmation of this bug, and a rough cause of
it.  Unfortunately I have not had the time to unscramble it, and neither
it seems has anyone else.

Eric