Re: sysfs group not found for kobject on mpt2sas unload

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On Mon, 25 Nov 2013 11:23:39 -0500
Joe Lawrence <joe.lawrence@xxxxxxxxxxx> wrote:

> On Wed, 20 Nov 2013 14:08:40 -0500
> Joe Lawrence <joe.lawrence@xxxxxxxxxxx> wrote:
> 
> > Starting in 3.12, when loading and unloading the mpt2sas driver, I see
> > the following warning:
> > 
> > ------------[ cut here ]------------
> > WARNING: CPU: 20 PID: 19096 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0()
> > sysfs group ffffffff81ca2f40 not found for kobject 'end_device-30:0'
> > Modules linked in: mpt2sas(-) stap_edcc1781e2697fc53c3d320bc2530218_19063(OF) ebtable_nat osst nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6table_nat nf_nat_ipv6 ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 iptable_nat nf_nat_ipv4 nf_nat iptable_mangle nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack bonding ebtable_filter ebtables ip6table_filter ip6_tables ixgbe igb x86_pkg_temp_thermal ptp coretemp pps_core joydev mdio crc32_pclmul crc32c_intel raid_class pcspkr ghash_clmulni_intel scsi_transport_sas ipmi_si dca ipmi_msghandler ntb uinput dm_round_robin sd_mod qla2xxx syscopyarea sysfillrect sysimgblt i2c_algo_bit drm_kms_helper ttm drm scsi_transport_fc scsi_tgt usb_storage i2c_core dm_multipath [last unloaded: stap_2da929a187c82c607a23237c27bf2d06_18803]
> > CPU: 20 PID: 19096 Comm: rmmod Tainted: GF       W  O 3.12.0+ #4
> > Hardware name: Stratus ftServer 6400/G7LAZ, BIOS BIOS Version 6.2:52 04/09/2013
> >  0000000000000009 ffff88083ad3bb88 ffffffff8165265e ffff88083ad3bbd0
> >  ffff88083ad3bbc0 ffffffff8105514d 0000000000000000 ffffffff81ca2f40
> >  ffff880851f46ef8 ffff88007a73cf38 ffff88083fb8c6e8 ffff88083ad3bc20
> > Call Trace:
> >  [<ffffffff8165265e>] dump_stack+0x4d/0x66
> >  [<ffffffff8105514d>] warn_slowpath_common+0x7d/0xa0
> >  [<ffffffff810551bc>] warn_slowpath_fmt+0x4c/0x50
> >  [<ffffffff8121873e>] ? sysfs_get_dirent_ns+0x4e/0x70
> >  [<ffffffff81219a46>] sysfs_remove_group+0xc6/0xd0
> >  [<ffffffff813edb43>] dpm_sysfs_remove+0x43/0x50
> >  [<ffffffff813e38c5>] device_del+0x45/0x1c0
> >  [<ffffffff813e3a5e>] device_unregister+0x1e/0x60
> >  [<ffffffff812eb9ce>] bsg_unregister_queue+0x5e/0xa0
> >  [<ffffffffa00dd0ba>] sas_rphy_free+0x7a/0xb0 [scsi_transport_sas]
> >  [<ffffffffa00def95>] sas_port_delete+0x35/0x160 [scsi_transport_sas]
> >  [<ffffffff81218c53>] ? sysfs_remove_link+0x23/0x30
> >  [<ffffffffa023662a>] mpt2sas_transport_port_remove+0x19a/0x1e0 [mpt2sas]
> >  [<ffffffffa0227b10>] _scsih_remove_device+0xb0/0x100 [mpt2sas]
> >  [<ffffffffa022f519>] mpt2sas_device_remove_by_sas_address.part.54+0x59/0x80 [mpt2sas]
> >  [<ffffffffa02322f9>] _scsih_remove+0xf9/0x210 [mpt2sas]
> >  [<ffffffff8133108b>] pci_device_remove+0x3b/0xb0
> >  [<ffffffff813e759f>] __device_release_driver+0x7f/0xf0
> >  [<ffffffff813e7f20>] driver_detach+0xc0/0xd0
> >  [<ffffffff813e71d5>] bus_remove_driver+0x55/0xd0
> >  [<ffffffff813e853c>] driver_unregister+0x2c/0x50
> >  [<ffffffff8132fbb3>] pci_unregister_driver+0x23/0x80
> >  [<ffffffffa023b713>] _scsih_exit+0x25/0x912 [mpt2sas]
> >  [<ffffffff810c93ed>] SyS_delete_module+0x16d/0x2d0
> >  [<ffffffff8165d81e>] ? do_page_fault+0xe/0x10
> >  [<ffffffff81661dd2>] system_call_fastpath+0x16/0x1b
> > ---[ end trace b4eef98870c871fd ]---
> > 
> > Instrumenting the module loading/unloading cycle with systemtap, it
> > reports the following sequence of events:
> > 
> > modprobe
> >   device_add(A)
> >   device_add(B child of A)
> >   device_add(C child of A)
> >   device_add(D child of A)
> > 
> > rmmod
> >   device_del(B child of A)
> >   device_del(C child of A)
> >   device_del(A)
> >   device_del(D child of A)             << WARNING
> > 
> > The same sequence of device_add/del events occur in 3.11, but without
> > the warning.  Git bisect shows bcdde7e221a8750f9b62b6d0bd31b72ea4ad9309
> > "sysfs: make __sysfs_remove_dir() recursive" as the first bad commit.
> > 
> 
> FWIW, I applied Mika's patch that Tejun posted the other day, "sysfs:
> handle duplicate removal attempts in sysfs_remove_group()" [1] and the
> warning goes away on mpt2sas unload.
> 
> [1] http://git.kernel.org/cgit/linux/kernel/git/tj/misc.git/commit/?h=review-sysfs-fixes&id=a69cc96d8c434c6cb64847f37caa890af705fc5c
> 
> -- Joe

Hi James,

(Correction, the sysfs change introducing the warning is 3.13-rc1+, not
3.12.)

Also, it seems that in 3.13-rc2, the patch from Mika that I had
referenced was reverted and that bug handled separately.

  81440e7 Revert "sysfs: handle duplicate removal attempts in sysfs_remove_group()"
  54d7114 sysfs: handle duplicate removal attempts in sysfs_remove_group()

So in 3.13-rc2, the warning persists when loading and unloading the
mpt2sas driver.

I looked at the code again, and I'm not sure why the sas_bsg_remove call
was placed in sas_rphy_free and not sas_rphy_remove.

The sas_rphy_remove function is tasked with undoing the actions of
sas_rphy_add ... so callers of sas_rphy_free are expecting that
everything sas_rphy_add had setup (if it was even called) has been
cleaned up.

Since bsg components are initialized by sas_rphy_add, does it make sense
for their destructor to live in sas_rphy_remove?

I've tested that change against a few mpt2sas driver load and unload
cycles without incident or sysfs warning.  If the placement of the
sas_bsg_remove call is important where it is, then a more substantial
change may be required to delete devices in an order that appeases
sysfs.

Thanks,

-- Joe
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