Re: sysfs: Kernel OOPS when install and remove modules

From: Hillf Danton
Date: Mon Mar 11 2013 - 00:58:54 EST

On Mon, Mar 11, 2013 at 10:55 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Mar 11, 2013 at 10:17:13AM +0800, Gao feng wrote:
>> I get the below stack when I execute the shell program
>> #!/bin/bash
>> while :;
>> do
>> modprobe 8139too&
>> rmmod 8139too&
>> done
>> I trust it is not the problem of 8139too, the other modules have the same problems too.
>> Is this an already known problem?
>> [ 53.328212] 8139too: 8139too Fast Ethernet driver 0.9.28
>> [ 53.368029] 8139too: module is already loaded
>> [ 53.456339] 8139too: 8139too Fast Ethernet driver 0.9.28
>> [ 53.510611] 8139too: 8139too Fast Ethernet driver 0.9.28
>> [ 53.551713] ------------[ cut here ]------------
>> [ 53.551721] WARNING: at include/linux/kref.h:42 kobject_get+0x33/0x40()
>> [ 53.551722] Hardware name: Bochs
>> [ 53.551723] Modules linked in: 8139too(+) ebtable_nat ipt_MASQUERADE nf_conntrack_netbios_ns nf_conntrack_broadcast ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 iptable_nat nf_nat
>> iptable_mangle nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ebtable_filter bnep ebtables bluetooth rfkill ip6table_filter ip6_tables be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4
>> cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device
>> snd_pcm snd_page_alloc snd_timer microcode snd i2c_piix4 virtio_balloon 8139cp soundcore mii i2c_core uinput [last unloaded: 8139too]
>> [ 53.551757] Pid: 1158, comm: modprobe Not tainted 3.6.10-4.fc18.x86_64 #1
> Does this happen on a kernel release?
> There's nothing I can do with a fedora kernel, sorry.
The comment says
* kref_put - decrement refcount for object.
* @kref: object.
* @release: pointer to the function that will clean up the object when the
* last reference to the object is released.
* This pointer is required, and it is not acceptable to pass kfree
* in as this function. If the caller does pass kfree to this
* function, you will be publicly mocked mercilessly by the kref
* maintainer, and anyone else who happens to notice it. You have
* been warned.
* Decrement the refcount, and if 0, call release().
* Return 1 if the object was removed, otherwise return 0. Beware, if this
* function returns 0, you still can not count on the kref from remaining in
* memory. Only use the return value if you want to see if the kref is now
* gone, not present.

and the release callback is called too late since we have to
/* remove the kobject from its kset's list */ even if refcount
drops to zero.

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