48ddbe19 "cgroup: make css->refcnt clearing on cgroup removal
optional" allowed a css to linger after the associated cgroup is
removed.  As a css holds a reference on the cgroup's dentry, it means
that cgroup dentries may linger for a while.

Destroying a superblock which has dentries with positive refcnts is a
critical bug and triggers BUG() in vfs code.  As each cgroup dentry
holds an s_active reference, any lingering cgroup has both its dentry
and the superblock pinned and thus preventing premature release of
superblock.

Unfortunately, after 48ddbe19, there's a small window while
releasing a cgroup which is directly under the root of the hierarchy.
When a cgroup directory is released, vfs layer first deletes the
corresponding dentry and then invokes dput() on the parent, which may
recurse further, so when a cgroup directly below root cgroup is
released, the cgroup is first destroyed - which releases the s_active
it was holding - and then the dentry for the root cgroup is dput().

This creates a window where the root dentry's refcnt isn't zero but
superblock's s_active is.  If umount happens before or during this
window, vfs will see the root dentry with non-zero refcnt and trigger
BUG().

Before 48ddbe19, this problem didn't exist because the last dentry
reference was guaranteed to be put synchronously from rmdir(2)
invocation which holds s_active around the whole process.

Fix it by holding an extra superblock->s_active reference across
dput() from css release, which is the dput() path added by 48ddbe19
and the only one which doesn't hold an extra s_active ref across the
final cgroup dput().
Signed-off-by: NTejun Heo <tj@kernel.org>
LKML-Reference: <4FEEA5CB.8070809@huawei.com>
Reported-by: Nshyju pv <shyju.pv@huawei.com>
Tested-by: Nshyju pv <shyju.pv@huawei.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Acked-by: NLi Zefan <lizefan@huawei.com>

This reverts commit fa980ca8.  The
commit was an attempt to fix a race condition where a cgroup hierarchy
may be unmounted with positive dentry reference on root cgroup.  While
the commit made the race condition slightly more difficult to trigger,
the race was still there and could be reliably triggered using a
different test case.

Revert the incorrect fix.  The next commit will describe the race and
fix it correctly.
Signed-off-by: NTejun Heo <tj@kernel.org>
LKML-Reference: <4FEEA5CB.8070809@huawei.com>
Reported-by: Nshyju pv <shyju.pv@huawei.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Acked-by: NLi Zefan <lizefan@huawei.com>

Pull ARM fixes from Russell King:
 "Last merge window, we had some updates from Al cleaning up the signal
  restart handling.  These have caused some problems on ARM, and while
  Al has some fixes, we have some concerns with Al's patches but we've
  been unsuccesful with discussing this.

  We have got to the point where we need to do something, and we've
  decided that the best solution is to revert the appropriate commits
  until Al is able to reply to us.

  Also included here are four patches to fix warnings that I've noticed
  in my build system, and one fix for kprobes test code."

* 'fixes' of git://git.linaro.org/people/rmk/linux-arm:
  ARM: fix warning caused by wrongly typed arm_dma_limit
  ARM: fix warnings about atomic64_read
  ARM: 7440/1: kprobes: only test 'sub pc, pc, #1b-2b+8-2' on ARMv6
  ARM: 7441/1: perf: return -EOPNOTSUPP if requested mode exclusion is unavailable
  ARM: 7443/1: Revert "new way of handling ERESTART_RESTARTBLOCK"
  ARM: 7442/1: Revert "remove unused restart trampoline"
  ARM: fix set_domain() macro
  ARM: fix mach-versatile/pci.c warning

Merge tag 'ecryptfs-3.5-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tyhicks/ecryptfs

Pull eCryptfs fixes from Tyler Hicks:
 "Fixes an incorrect access mode check when preparing to open a file in
  the lower filesystem.  This isn't an urgent fix, but it is simple and
  the check was obviously incorrect.

  Also fixes a couple important bugs in the eCryptfs miscdev interface.
  These changes are low risk due to the small number of users that use
  the miscdev interface.  I was able to keep the changes minimal and I
  have some cleaner, more complete changes queued up for the next merge
  window that will build on these patches."

* tag 'ecryptfs-3.5-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tyhicks/ecryptfs:
  eCryptfs: Gracefully refuse miscdev file ops on inherited/passed files
  eCryptfs: Fix lockdep warning in miscdev operations
  eCryptfs: Properly check for O_RDONLY flag before doing privileged open

Pull target fixes from Nicholas Bellinger:
 "Two minor target fixes.  There is really nothing exciting and/or
  controversial this time around.

  There's one fix from MDR for a RCU debug warning message within tcm_fc
  code (CC'ed to stable), and a small AC fix for qla_target.c based upon
  a recent Coverity static report.

  Also, there is one other outstanding virtio-scsi LUN scanning bugfix
  that has been uncovered with the in-flight tcm_vhost driver over the
  last days, and that needs to make it into 3.5 final too.  This patch
  has been posted to linux-scsi again here:

    http://marc.info/?l=linux-scsi&m=134160609212542&w=2

  and I've asked James to include it in his next PULL request."

* git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending:
  qla2xxx: print the right array elements in qlt_async_event
  tcm_fc: Resolve suspicious RCU usage warnings

File operations on /dev/ecryptfs would BUG() when the operations were
performed by processes other than the process that originally opened the
file. This could happen with open files inherited after fork() or file
descriptors passed through IPC mechanisms. Rather than calling BUG(), an
error code can be safely returned in most situations.

In ecryptfs_miscdev_release(), eCryptfs still needs to handle the
release even if the last file reference is being held by a process that
didn't originally open the file. ecryptfs_find_daemon_by_euid() will not
be successful, so a pointer to the daemon is stored in the file's
private_data. The private_data pointer is initialized when the miscdev
file is opened and only used when the file is released.

https://launchpad.net/bugs/994247Signed-off-by: NTyler Hicks <tyhicks@canonical.com>
Reported-by: NSasha Levin <levinsasha928@gmail.com>
Tested-by: NSasha Levin <levinsasha928@gmail.com>

Based upon Alan's patch from Coverity scan id 793583, these debug
messages in qlt_async_event() should be starting from byte 0, which is
always the Asynchronous Event Status Code from the parent switch statement.

Also, rename reason_code -> login_code following the language used in
2500 FW spec for Port Database Changed (0x8014) -> Port Database Changed
Event Mailbox Register for mailbox[2].
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Cc: Chad Dupuis <chad.dupuis@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Use rcu_dereference_protected to tell rcu that the ft_lport_lock
is held during ft_lport_create. This resolved "suspicious RCU usage"
warnings when debugging options are turned on.
Signed-off-by: NMark Rustad <mark.d.rustad@intel.com>
Tested-by: NRoss Brattain <ross.b.brattain@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Pull two MTD fixes from David Woodhouse:
 - Fix a logic error in OLPC CAFÉ NAND ready() function.
 - Fix regression due to bitflip handling changes.

* tag 'for-linus-20120706' of git://git.infradead.org/linux-mtd:
  mtd: cafe_nand: fix an & vs | mistake
  mtd: nand: initialize bitflip_threshold prior to BBT scanning

Otherwise the code races with munmap (causing a use-after-free
of the vma) or with close (causing a use-after-free of the struct
file).

The bug was introduced by commit 90ed52eb ("[PATCH] holepunch: fix
mmap_sem i_mutex deadlock")

Cc: Hugh Dickins <hugh@veritas.com>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull ocfs2 fixes from Joel Becker.

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/ocfs2:
  aio: make kiocb->private NUll in init_sync_kiocb()
  ocfs2: Fix bogus error message from ocfs2_global_read_info
  ocfs2: for SEEK_DATA/SEEK_HOLE, return internal error unchanged if ocfs2_get_clusters_nocache() or ocfs2_inode_lock() call failed.
  ocfs2: use spinlock irqsave for downconvert lock.patch
  ocfs2: Misplaced parens in unlikley
  ocfs2: clear unaligned io flag when dio fails

Pull cifs fixes from Steve French.

* git://git.samba.org/sfrench/cifs-2.6:
  cifs: when server doesn't set CAP_LARGE_READ_X, cap default rsize at MaxBufferSize
  cifs: fix parsing of password mount option

Pull input layer fixes from Dmitry Torokhov:
 "Two fixes for regressions in Wacom driver and fixes for drivers using
  threaded IRQ framework without specifying IRQF_ONESHOT."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: request threaded-only IRQs with IRQF_ONESHOT
  Input: wacom - don't retrieve touch_max when it is predefined
  Input: wacom - fix retrieving touch_max bug
  Input: fix input.h kernel-doc warning

The intent here was clearly to set result to true if the 0x40000000 flag
was set.  But instead there was a | vs & typo and we always set result
to true.

Artem: check the spec at
wiki.laptop.org/images/5/5c/88ALP01_Datasheet_July_2007.pdf
and this fix looks correct.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

Pull ARM SoC fixes from Arnd Bergmann:
 "Small fixes on multiple ARM platforms
   - A build regression from a previous fix on dove and mv78xx0
   - Two fixes for recently (3.5-rc1) changed mmp/pxa code
   - multiple omap2+ bug fixes
   - two trivial fixes for i.MX
   - one v3.5 regression for mxs"

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  ARM: apx4devkit: fix FEC enabling PHY clock
  ARM: OMAP2+: hwmod data: Fix wrong McBSP clock alias on OMAP4
  ARM: OMAP4: hwmod data: temporarily comment out data for the usb_host_fs and aess IP blocks
  ARM: Orion: Fix WDT compile for Dove and MV78xx0
  ARM: mmp: remove mach/gpio-pxa.h
  ARM: imx: assert SCC gate stays enabled
  ARM: OMAP4: TWL6030: ensure sys_nirq1 is mux'd and wakeup enabled
  ARM: OMAP2: Overo: init I2C before MMC to fix MMC suspend/resume failure
  ARM: imx27_visstrim_m10: Do not include <asm/system.h>
  ARM: pxa: hx4700: Fix basic suspend/resume

Pull KVM fix from Marcelo Tosatti:
 "Memory leak and oops on the x86 mmu code, and sanitization of the
  KVM_IRQFD ioctl."

* git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: MMU: fix shrinking page from the empty mmu
  KVM: fix fault page leak
  KVM: Sanitize KVM_IRQFD flags
  KVM: Add missing KVM_IRQFD API documentation
  KVM: Pass kvm_irqfd to functions

Pull leds fix from Bryan Wu:
 "Fix for heartbeat led trigger driver"

* 'fixes-for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds:
  leds: heartbeat: fix bug on panic

Pull btrfs updates from Chris Mason:
 "I held off on my rc5 pull because I hit an oops during log recovery
  after a crash.  I wanted to make sure it wasn't a regression because
  we have some logging fixes in here.

  It turns out that a commit during the merge window just made it much
  more likely to trigger directory logging instead of full commits,
  which exposed an old bug.

  The new backref walking code got some additional fixes.  This should
  be the final set of them.

  Josef fixed up a corner where our O_DIRECT writes and buffered reads
  could expose old file contents (not stale, just not the most recent).
  He and Liu Bo fixed crashes during tree log recover as well.

  Ilya fixed errors while we resume disk balancing operations on
  readonly mounts."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: run delayed directory updates during log replay
  Btrfs: hold a ref on the inode during writepages
  Btrfs: fix tree log remove space corner case
  Btrfs: fix wrong check during log recovery
  Btrfs: use _IOR for BTRFS_IOC_SUBVOL_GETFLAGS
  Btrfs: resume balance on rw (re)mounts properly
  Btrfs: restore restriper state on all mounts
  Btrfs: fix dio write vs buffered read race
  Btrfs: don't count I/O statistic read errors for missing devices
  Btrfs: resolve tree mod log locking issue in btrfs_next_leaf
  Btrfs: fix tree mod log rewind of ADD operations
  Btrfs: leave critical region in btrfs_find_all_roots as soon as possible
  Btrfs: always put insert_ptr modifications into the tree mod log
  Btrfs: fix tree mod log for root replacements at leaf level
  Btrfs: support root level changes in __resolve_indirect_ref
  Btrfs: avoid waiting for delayed refs when we must not

Pull DT fixes from Rob Herring:
 "Mainly some documentation updates and 2 fixes:

   - An export symbol fix for of_platform_populate from Stephen W.
   - A fix for the order compatible entries are matched to ensure the
     first compatible string is matched when there are multiple matches."

Normally these would go through Grant Likely (thus the "fixes-for-grant"
branch name), but Grant is in the middle of moving to Scotland, and is
practically offline until sometime in August. So pull directly from Rob.

* 'fixes-for-grant' of git://sources.calxeda.com/kernel/linux:
  of: match by compatible property first
  dt: mc13xxx.txt: Fix gpio number assignment
  dt: fsl-fec.txt: Fix gpio number assignment
  dt: fsl-mma8450.txt: Add missing 'reg' description
  dt: fsl-imx-esdhc.txt: Fix gpio number assignment
  dt: fsl-imx-cspi.txt: Fix comment about GPIOs used for chip selects
  of: Add Avionic Design vendor prefix
  of: export of_platform_populate()

arch/arm/mm/init.c: In function 'arm_memblock_init':
arch/arm/mm/init.c:380: warning: comparison of distinct pointer types lacks a cast

by fixing the typecast in its definition when DMA_ZONE is disabled.
This was missed in 4986e5c7 (ARM: mm: fix type of the arm_dma_limit
global variable).
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Fix:
net/netfilter/xt_connbytes.c: In function 'connbytes_mt':
net/netfilter/xt_connbytes.c:43: warning: passing argument 1 of 'atomic64_read' discards qualifiers from pointer target type
...

by adding the missing const.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

'sub pc, pc, #1b-2b+8-2' results in address<1:0> == '10'.

sub pc, pc, #const (== ADR pc, #const) performs an interworking branch
(BXWritePC()) on ARMv7+ and a simple branch (BranchWritePC()) on earlier
versions.

In ARM state, BXWritePC() is UNPREDICTABLE when address<1:0> == '10'.

In ARM state on ARMv6+, BranchWritePC() ignores address<1:0>.  Before
ARMv6, BranchWritePC() is UNPREDICTABLE if address<1:0> != '00'

So the instruction is UNPREDICTABLE both before and after v6.
Acked-by: NJon Medhurst <tixy@yxit.co.uk>
Signed-off-by: NRabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Merge tag 'omap-fixes-for-v3.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into fixes

PM related fixes for omaps mostly to get suspend/resume
working again.

* tag 'omap-fixes-for-v3.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  ARM: OMAP2+: hwmod data: Fix wrong McBSP clock alias on OMAP4
  ARM: OMAP4: hwmod data: temporarily comment out data for the usb_host_fs and aess IP blocks
  ARM: OMAP4: TWL6030: ensure sys_nirq1 is mux'd and wakeup enabled
  ARM: OMAP2: Overo: init I2C before MMC to fix MMC suspend/resume failure
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

* 'mxs/fixes-for-3.5' of git://git.linaro.org/people/shawnguo/linux-2.6:
  ARM: apx4devkit: fix FEC enabling PHY clock
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

We currently return -EPERM if the user requests mode exclusion that is
not supported by the CPU. This looks pretty confusing from userspace
and is inconsistent with other architectures (ppc, x86).

This patch returns -EOPNOTSUPP instead.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This reverts commit 6b5c8045.

Conflicts:

	arch/arm/kernel/ptrace.c

The new syscall restarting code can lead to problems if we take an
interrupt in userspace just before restarting the svc instruction. If
a signal is delivered when returning from the interrupt, the
TIF_SYSCALL_RESTARTSYS will remain set and cause any syscalls executed
from the signal handler to be treated as a restart of the previously
interrupted system call. This includes the final sigreturn call, meaning
that we may fail to exit from the signal context. Furthermore, if a
system call made from the signal handler requires a restart via the
restart_block, it is possible to clear the thread flag and fail to
restart the originally interrupted system call.

The right solution to this problem is to perform the restarting in the
kernel, avoiding the possibility of handling a further signal before the
restart is complete. Since we're almost at -rc6, let's revert the new
method for now and aim for in-kernel restarting at a later date.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This reverts commit fa18484d.

We need the restart trampoline back so that we can revert a related
problematic patch 6b5c8045 ("arm: new
way of handling ERESTART_RESTARTBLOCK").
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Avoid polluting drivers with a set_domain() macro, which interferes with
structure member names:

drivers/net/wireless/ath/ath9k/dfs_pattern_detector.c:294:33: error: macro "set_domain" passed 2 arguments, but takes just 1
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Ocfs2 uses kiocb.*private as a flag of unsigned long size. In
commit a11f7e63 ocfs2: serialize unaligned aio, the unaligned
io flag is involved in it to serialize the unaligned aio. As
*private is not initialized in init_sync_kiocb() of do_sync_write(),
this unaligned io flag may be unexpectly set in an aligned dio.
And this will cause OCFS2_I(inode)->ip_unaligned_aio decreased
to -1 in ocfs2_dio_end_io(), thus the following unaligned dio
will hang forever at ocfs2_aiodio_wait() in ocfs2_file_aio_write().
Signed-off-by: NJunxiao Bi <junxiao.bi@oracle.com>
Cc: stable@vger.kernel.org
Acked-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJoel Becker <jlbec@evilplan.org>

Merge tag 'omap-fixes-b-for-3.5rc' of git://git.kernel.org/pub/scm/linux/kernel/git/pjw/omap-pending into fixes

A few more OMAP fixes for 3.5-rc.  These fix some bugs with power
management and McBSP.

Ethernet stopped to work after mxs clk framework change.
Signed-off-by: NLauri Hintsala <lauri.hintsala@bluegiga.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

Since commit 1c6c6952 ("genirq: Reject bogus threaded irq requests")
threaded IRQs without a primary handler need to be requested with
IRQF_ONESHOT, otherwise the request will fail. This patch adds the
IRQF_ONESHOT to input drivers where it is missing. Not modified by
this patch are those drivers where the requested IRQ will always be a
nested IRQ (e.g. because it's part of an MFD), since for this special
case IRQF_ONESHOT is not required to be specified when requesting the
IRQ.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

arch/arm/mach-versatile/pci.c: In function 'versatile_map_irq':
arch/arm/mach-versatile/pci.c:342: warning: unused variable 'devslot'
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

The commit 503d0ea2
  ARM: OMAP4: hwmod data: Add aliases for McBSP fclk clocks

added a wrong "prcm_clk" alias for PRCM clock whereas the McBSP
driver and previous OMAPs are using "prcm_fck".

It thus lead to the following warning.

[   47.409729] omap-mcbsp: clks: could not clk_get() prcm_fck

Fix that by changing the opt_clk role to prcm_fck.
Reported-by: NMisael Lopez Cruz <misael.lopez@ti.com>
Signed-off-by: NBenoit Cousson <b-cousson@ti.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: NSebastien Guiriec <s-guiriec@ti.com>
Signed-off-by: NPaul Walmsley <paul@pwsan.com>

The OMAP4 usb_host_fs (OHCI) and AESS IP blocks require some special
programming for them to enter idle.  Without this programming, they
will prevent the rest of the chip from entering full chip idle.

To implement the idle programming cleanly, this will take some
coordination between maintainers.  This is likely to take some time,
so it is probably best to leave this for 3.6 or 3.7.  So, in the
meantime, prevent these IP blocks from being registered.

Later, once the appropriate support is available, this patch can be
reverted.

This second version comments out the IP block data since Benoît didn't
like removing it.
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Cc: Benoît Cousson <b-cousson@ti.com>

From Haojian Zhuang <haojian.zhuang@gmail.com>:

* 'fixes' of git://github.com/hzhuang1/linux:
  ARM: mmp: remove mach/gpio-pxa.h
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

From Sascha Hauer <s.hauer@pengutronix.de>:

ARM i.MX fixes for v3.5-rc5

* tag 'v3.5-imx-fixes' of git://git.pengutronix.de/git/imx/linux-2.6:
  ARM: imx: assert SCC gate stays enabled
  ARM: imx27_visstrim_m10: Do not include <asm/system.h>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

Commit 0fa1f060 (ARM: Orion: Fix
Virtual/Physical mixup with watchdog) broke the Dove & MV78xx0
build. Although these two SoC don't use the watchdog, the shared
platform code still needs to build. Add the necessary defines.

Cc: stable@vger.kernel.org
Reported-by: NNicolas Pitre <nico@fluxnic.net>
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Tested-by: NNicolas Pitre <nico@fluxnic.net>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

Commit 157d2644 ("ARM: pxa: change gpio
to platform device") removed all includes of mach/gpio-pxa.h. It kept
this unused header in the tree. Using it can't work, as it itself
includes the non-existent header plat/gpio-pxa.h. This header can safely
be removed.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Acked-by: NEric Miao <eric.y.miao@gmail.com>
Signed-off-by: NHaojian Zhuang <haojian.zhuang@gmail.com>

With commit 49dca5ae I introduced
a bug (visible if CONFIG_PROVE_RCU is enabled) which occures when a panic
has happened:

[ 1526.520230] ===============================
[ 1526.520230] [ INFO: suspicious RCU usage. ]
[ 1526.520230] 3.5.0-rc1+ #12 Not tainted
[ 1526.520230] -------------------------------
[ 1526.520230] /c/kernel-tests/mm/include/linux/rcupdate.h:436 Illegal context switch in RCU read-side critical section!
[ 1526.520230]
[ 1526.520230] other info that might help us debug this:
[ 1526.520230]
[ 1526.520230]
[ 1526.520230] rcu_scheduler_active = 1, debug_locks = 0
[ 1526.520230] 3 locks held by net.agent/3279:
[ 1526.520230]  #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff82f85962>] do_page_fault+0x193/0x390
[ 1526.520230]  #1:  (panic_lock){+.+...}, at: [<ffffffff82ed2830>] panic+0x37/0x1d3
[ 1526.520230]  #2:  (rcu_read_lock){.+.+..}, at: [<ffffffff810b9b28>] rcu_lock_acquire+0x0/0x29
[ 1526.520230]
[ 1526.520230] stack backtrace:
[ 1526.520230] Pid: 3279, comm: net.agent Not tainted 3.5.0-rc1+ #12
[ 1526.520230] Call Trace:
[ 1526.520230]  [<ffffffff810e1570>] lockdep_rcu_suspicious+0x109/0x112
[ 1526.520230]  [<ffffffff810bfe3a>] rcu_preempt_sleep_check+0x45/0x47
[ 1526.520230]  [<ffffffff810bfe5a>] __might_sleep+0x1e/0x19a
[ 1526.520230]  [<ffffffff82f8010e>] down_write+0x26/0x81
[ 1526.520230]  [<ffffffff8276a966>] led_trigger_unregister+0x1f/0x9c
[ 1526.520230]  [<ffffffff8276def5>] heartbeat_reboot_notifier+0x15/0x19
[ 1526.520230]  [<ffffffff82f85bf5>] notifier_call_chain+0x96/0xcd
[ 1526.520230]  [<ffffffff82f85cba>] __atomic_notifier_call_chain+0x8e/0xff
[ 1526.520230]  [<ffffffff81094b7c>] ? kmsg_dump+0x37/0x1eb
[ 1526.520230]  [<ffffffff82f85d3f>] atomic_notifier_call_chain+0x14/0x16
[ 1526.520230]  [<ffffffff82ed28e1>] panic+0xe8/0x1d3
[ 1526.520230]  [<ffffffff811473e2>] out_of_memory+0x15d/0x1d3

So in case of a panic, now just turn of the LED. Other approaches like
scheduling a work to unregister the trigger aren't working because there
isn't much which still runs after a panic occured (except timers).
Signed-off-by: NAlexander Holler <holler@ahsoftware.de>
Signed-off-by: NBryan Wu <bryan.wu@canonical.com>