Re: [Bug] 12.864681 BUG: lock held when returning to user space!

[Douglas Gilbert]

On 13-10-08 02:44 AM, vaughan wrote:
> Hi Madper,
>
> CC to Douglas to get comments.
> I use the rw_semaphore o_sem to protect excl open, introduced in commit
> 15b06f9a02406e5460001db6d5af5c738cd3d4e7 since v3.12-rc1.
> Is it forbidden to do like that in kernel?...

It appears you can not (allow sg_open() to hold a semaphore
then return to the user space). So you will need to do some
rework on that patch or revert it.

Doug Gilbert

Reference: scsi-linux + kernel lists, title:
  [PATCH v6 0/4][SCSI] sg: fix race condition in sg_open
  20130828

> On 10/08/2013 01:57 PM, Madper Xie wrote:
> > Howdy Vaughan Cao,
> >     I can't meet this issue on both 3.11 and 3.11.4. There are only four
> >     patches between 3.11 and 3.12-rc2 and you are the author. Will you
> >     please check them if you have time.
> >
> > cxie@xxxxxxxxxx writes:
> >
> > > Hi all,
> > >     With kernel3.12-rc2 the dmesg shows following logs:
> > > [   12.864680] ================================================
> > > [   12.864681] [ BUG: lock held when returning to user space! ]
> > > [   12.864682] 3.12.0-rc2 #1 Not tainted
> > > [   12.864683] ------------------------------------------------
> > > [   12.864684] iprinit/719 is leaving the kernel with locks still held!
> > > [   12.864685] 1 lock held by iprinit/719:
> > > [   12.864686]  #0:  (&sdp->o_sem){.+.+..}, at: [<ffffffffa050de05>] sg_open+0x4b5/0x644 [sg]
> > > [   12.934954] ath9k 0000:01:00.0: enabling device (0000 -> 0002)
> > > [   12.940346] ath: phy0: timeout (1000 us) on reg 0x15f18: 0x00000000 & 0x00000007 != 0x00000004
> > > [   12.943125] ath: EEPROM regdomain: 0x60
> > > [   12.943127] ath: EEPROM indicates we should expect a direct regpair map
> > > [   12.943129] ath: Country alpha2 being used: 00
> > > [   12.943130] ath: Regpair used: 0x60
> > > [   12.960202] r8169 0000:02:00.0 p3p1: link down
> > > [   12.960236] r8169 0000:02:00.0 p3p1: link down
> > > [   12.960256] IPv6: ADDRCONF(NETDEV_UP): p3p1: link is not ready
> > > [   13.003523] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
> > > [   13.003886] ieee80211 phy0: Atheros AR9485 Rev:1 mem=0xffffc9000bc80000, irq=16
> > > [   13.012120] ip6_tables: (C) 2000-2006 Netfilter Core Team
> > > [   13.023667] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
> > > [   13.055802] Ebtables v2.0 registered
> > > [   13.192291] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
> > > [   15.906392] r8169 0000:02:00.0 p3p1: link up
> > > [   15.906416] IPv6: ADDRCONF(NETDEV_CHANGE): p3p1: link becomes ready
> > > [   17.121989] systemd-udevd (334) used greatest stack depth: 3352 bytes left
> > >
> > > I'm working on finding which version bring this bug in.

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