> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> /home/greearb/git/linux.wireless-testing/kernel/sched.c:618 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 1
> 1 lock held by ifup/23517:
>   #0:  (&rq->lock){-.-.-.}, at: [<c042f782>] task_fork_fair+0x3b/0x108
>
> stack backtrace:
> Pid: 23517, comm: ifup Not tainted 2.6.36-rc6-wl+ #5
> Call Trace:
>   [<c075e219>] ? printk+0xf/0x16
>   [<c0455842>] lockdep_rcu_dereference+0x74/0x7d
>   [<c0426854>] task_group+0x6d/0x79
>   [<c042686e>] set_task_rq+0xe/0x57
>   [<c042f79e>] task_fork_fair+0x57/0x108
>   [<c042e965>] sched_fork+0x82/0xf9
>   [<c04334b3>] copy_process+0x569/0xe8e
>   [<c0433ef0>] do_fork+0x118/0x262
>   [<c076302f>] ? do_page_fault+0x16a/0x2cf
>   [<c044b80c>] ? up_read+0x16/0x2a
>   [<c04085ae>] sys_clone+0x1b/0x20
>   [<c04030a5>] ptregs_clone+0x15/0x30
>   [<c0402f1c>] ? sysenter_do_call+0x12/0x38

Here a newly created task is having its runqueue assigned.  The new task
is not yet on the tasklist, so cannot go away.  This is therefore a false
positive, suppress with an RCU read-side critical section.

Reported-by: Ben Greear <greearb@candelatech.com
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Ben Greear <greearb@candelatech.com

> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> include/linux/cgroup.h:542 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 0
> 1 lock held by swapper/1:
>  #0:  (net_mutex){+.+.+.}, at: [<ffffffff813e9010>]
> register_pernet_subsys+0x1f/0x47
>
> stack backtrace:
> Pid: 1, comm: swapper Not tainted 2.6.35.4-28.fc14.x86_64 #1
> Call Trace:
>  [<ffffffff8107bd3a>] lockdep_rcu_dereference+0xaa/0xb3
>  [<ffffffff813e04b9>] sock_update_classid+0x7c/0xa2
>  [<ffffffff813e054a>] sk_alloc+0x6b/0x77
>  [<ffffffff8140b281>] __netlink_create+0x37/0xab
>  [<ffffffff813f941c>] ? rtnetlink_rcv+0x0/0x2d
>  [<ffffffff8140cee1>] netlink_kernel_create+0x74/0x19d
>  [<ffffffff8149c3ca>] ? __mutex_lock_common+0x339/0x35b
>  [<ffffffff813f7e9c>] rtnetlink_net_init+0x2e/0x48
>  [<ffffffff813e8d7a>] ops_init+0xe9/0xff
>  [<ffffffff813e8f0d>] register_pernet_operations+0xab/0x130
>  [<ffffffff813e901f>] register_pernet_subsys+0x2e/0x47
>  [<ffffffff81db7bca>] rtnetlink_init+0x53/0x102
>  [<ffffffff81db835c>] netlink_proto_init+0x126/0x143
>  [<ffffffff81db8236>] ? netlink_proto_init+0x0/0x143
>  [<ffffffff810021b8>] do_one_initcall+0x72/0x186
>  [<ffffffff81d78ebc>] kernel_init+0x23b/0x2c9
>  [<ffffffff8100aae4>] kernel_thread_helper+0x4/0x10
>  [<ffffffff8149e2d0>] ? restore_args+0x0/0x30
>  [<ffffffff81d78c81>] ? kernel_init+0x0/0x2c9
>  [<ffffffff8100aae0>] ? kernel_thread_helper+0x0/0x10

The sock_update_classid() function calls task_cls_classid(current),
but the calling task cannot go away, so there is no danger of
the associated structures disappearing.  Insert an RCU read-side
critical section to suppress the false positive.
Reported-by: Subrata Modak <subrata@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Merge reason: Update from -rc3 to -rc7.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/rcu

* 'upstream' of git://git.linux-mips.org/pub/scm/upstream-linus:
  MIPS: Octeon: Place cnmips_cu2_setup in __init memory.
  MIPS: Don't place cu2 notifiers in __cpuinitdata
  MIPS: Calculate VMLINUZ_LOAD_ADDRESS based on the length of vmlinux.bin
  MIPS: Alchemy: Resolve prom section mismatches
  MIPS: Fix syscall 64 bit number comments.
  MIPS: Hookup fanotify_init, fanotify_mark, and prlimit64 syscalls.
  MIPS: TX49xx: Rename ARCH_KMALLOC_MINALIGN to ARCH_DMA_MINALIGN
  MIPS: N32: Fix getdents64 syscall for n32
  MIPS: Remove pr_<level> uses of KERN_<level>
  MIPS: PNX8550: Sort out machine halt, restart and powerdown functions.
  MIPS: GIC: Remove dependencies from Malta files.
  MIPS: Kconfig: Fix and clarify kconfig help text for VSMP and SMTC.
  MIPS: DMA: Fix computation of DMA flags from device's coherent_dma_mask.
  MIPS: Audit: Fix hang in entry.S.
  MIPS: Document why RELOC_HIDE is there.
  MIPS: Octeon: Determine if helper needs to be built
  MIPS: Use generic atomic64 for 32-bit kernels
  MIPS: RM7000: Symbol should be static
  MIPS: kspd: Adjust confusing if indentation
  MIPS: Fix a typo.

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  writeback: always use sb->s_bdi for writeback purposes

* 'v2.6.36-rc6-urgent-fixes' of git://xenbits.xen.org/people/sstabellini/linux-pvhvm:
  xen: do not initialize PV timers on HVM if !xen_have_vector_callback
  xen: do not set xenstored_ready before xenbus_probe on hvm

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Initialize total_len in fuse_retrieve()

Since powerpc uses -Werror on arch powerpc, the build was broken like
this:

  cc1: warnings being treated as errors
  arch/powerpc/kernel/module.c: In function 'module_finalize':
  arch/powerpc/kernel/module.c:66: error: unused variable 'err'
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

As suggested by Linus, push the irqs_disabled() down to the
rcu_read_lock_bh_held() level so that all callers get the benefit
of the correct check.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: rcu_read_lock_bh_held(): disabling irqs also disables bh
  generic-ipi: Fix deadlock in __smp_call_function_single

Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  perf trace scripting: Fix extern struct definitions
  perf ui hist browser: Fix segfault on 'a' for annotate
  perf tools: Fix build breakage
  perf, x86: Handle in flight NMIs on P4 platform
  oprofile, ARM: Release resources on failure
  oprofile: Add Support for Intel CPU Family 6 / Model 29

The "flags" member of "struct wait_queue_t" is used in several places in
the kernel code without beeing initialized by init_wait().  "flags" is
used in bitwise operations.

If "flags" not initialized then unexpected behaviour may take place.
Incorrect flags might used later in code.

Added initialization of "wait_queue_t.flags" with zero value into
"init_wait".
Signed-off-by: Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@nokia.com>
[ The bit we care about does end up being initialized by both
   prepare_to_wait() and add_to_wait_queue(), so this doesn't seem to
   cause actual bugs, but is definitely the right thing to do -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.
Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

if !xen_have_vector_callback do not initialize PV timer unconditionally
because we still don't know how many cpus are available and if there is
more than one we won't be able to receive the timer interrupts on
cpu > 0.

This patch fixes an hang at boot when Xen does not support vector
callbacks and the guest has multiple vcpus.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>

Register_xenstore_notifier should guarantee that the caller gets
notified even if xenstore is already up.
Therefore we revert "do not notify callers from
register_xenstore_notifier" and set xenstored_read at the right time for
PV on HVM guests too.
In fact in case of PV on HVM guests xenstored is ready only after the
platform pci driver has completed the initialization, so do not set
xenstored_ready before the call to xenbus_probe().

This patch fixes a shutdown_event watcher registration bug that causes
"xm shutdown" not to work properly.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lrg/voltage-2.6:
  regulator: max8649 - fix setting extclk_freq
  regulator: fix typo in current units
  regulator: fix device_register() error handling

* 'merge-powerpc' of git://git.secretlab.ca/git/linux-2.6:
  powerpc/5200: tighten up ac97 reset timing
  powerpc/5200: efika.c: Add of_node_put to avoid memory leak
  powerpc/512x: fix clk_get() return value

* 'fix/misc' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
  ALSA: i2c/other/ak4xx-adda: Fix a compile warning with CONFIG_PROCFS=n
  ALSA: prevent heap corruption in snd_ctl_new()

* 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/staging:
  hwmon: f71882fg: use a muxed resource lock for the Super I/O port

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
  [CPUFREQ] Fix memory leaks in pcc_cpufreq_do_osc
  [CPUFREQ] acpi-cpufreq: add missing __percpu markup

* 'merge-spi' of git://git.secretlab.ca/git/linux-2.6:
  of/spi: Fix OF-style driver binding of spi devices
  spi: spi-gpio.c tests SPI_MASTER_NO_RX bit twice, but not SPI_MASTER_NO_TX
  spi/mpc8xxx: fix buffer overrun on large transfers

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6:
  vlan: dont drop packets from unknown vlans in promiscuous mode
  Phonet: Correct header retrieval after pskb_may_pull
  um: Proper Fix for f25c80a4: remove duplicate structure field initialization
  ip_gre: Fix dependencies wrt. ipv6.
  net-2.6: SYN retransmits: Add new parameter to retransmits_timed_out()
  iwl3945: queue the right work if the scan needs to be aborted
  mac80211: fix use-after-free

* 'drm-intel-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ickle/drm-intel:
  drm/i915: Rephrase pwrite bounds checking to avoid any potential overflow
  drm/i915: Sanity check pread/pwrite
  drm/i915: Use pipe state to tell when pipe is off
  drm/i915: vblank status not valid while training display port
  drivers/gpu/drm/i915/i915_gem.c: Add missing error handling code
  drm/i915: Fix refleak during eviction.
  drm/i915: fix GMCH power reporting

Building under memory pressure, with KSM on 2.6.36-rc5, collapsed with
an internal compiler error: typically indicating an error in swapping.

Perhaps there's a timing issue which makes it now more likely, perhaps
it's just a long time since I tried for so long: this bug goes back to
KSM swapping in 2.6.33.

Notice how reuse_swap_page() allows an exclusive page to be reused, but
only does SetPageDirty if it can delete it from swap cache right then -
if it's currently under Writeback, it has to be left in cache and we
don't SetPageDirty, but the page can be reused.  Fine, the dirty bit
will get set in the pte; but notice how zap_pte_range() does not bother
to transfer pte_dirty to page_dirty when unmapping a PageAnon.

If KSM chooses to share such a page, it will look like a clean copy of
swapcache, and not be written out to swap when its memory is needed;
then stale data read back from swap when it's needed again.

We could fix this in reuse_swap_page() (or even refuse to reuse a
page under writeback), but it's more honest to fix my oversight in
KSM's write_protect_page().  Several days of testing on three machines
confirms that this fixes the issue they showed.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2.6.36-rc1 commit 21d0d443 "rmap:
resurrect page_address_in_vma anon_vma check" was right to resurrect
that check; but now that it's comparing anon_vma->roots instead of
just anon_vmas, there's a danger of oopsing on a NULL anon_vma.

In most cases no NULL anon_vma ever gets here; but it turns out that
occasionally KSM, when enabled on a forked or forking process, will
itself call page_address_in_vma() on a "half-KSM" page left over from
an earlier failed attempt to merge - whose page_anon_vma() is NULL.

It's my bug that those should be getting here at all: I thought they
were already dealt with, this oops proves me wrong, I'll fix it in
the next release - such pages are effectively pinned until their
process exits, since rmap cannot find their ptes (though swapoff can).

For now just work around it by making page_address_in_vma() safe (and
add a comment on why that check is wanted anyway).  A similar check
in __page_check_anon_rmap() is safe because do_page_add_anon_rmap()
already excluded KSM pages.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It is an early_initcall, so it should be in __init memory.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1593/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

The notifiers may be called at any time, so the notifier_block cannot
be in init memory.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1592/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Fix VMLINUZ_LOAD_ADDRESS calculation to be based on the length of
vmlinux.bin, the actual uncompressed kernel binary.

Previously it was based on the length of KBUILD_IMAGE (the unstripped ELF
vmlinux), which is bigger than vmlinux.bin.  As a result, vmlinuz was
loaded into a memory address higher then actually needed - a problem for
small memory platforms.
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
To: linux-mips@linux-mips.org
Cc: alex@digriz.org.uk
Cc: manuel.lauss@googlemail.com
Cc: sam@ravnborg.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1564/Acked-by: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

The function prom_init_cmdline() references the variable __initdata
arcs_cmdline.

The function prom_get_ethernet_addr() references the variable __initdata
arcs_cmdline.

Annotate prom_init_cmdline() as __init, unexport and annotate
prom_get_ethernet_addr() since it's no longer called from within
driver code.
Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/1547/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Noticed and original patch by Philby John <pjohn@mvista.com>.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1553/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Architectures need to set ARCH_DMA_MINALIGN to the minimum DMA
alignment (commit a6eb9fe1). Defining
ARCH_KMALLOC_MINALIGN doesn't work anymore.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: anemo@mba.ocn.ne.jp
Patchwork: https://patchwork.linux-mips.org/patch/1544/Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Commit 31c984a5 introduced a new syscall
getdents64. However, in the syscall table, the new syscall still refers to
the old getdents which doesn't work.

The problem appeared with a system that uses the eglibc 2.12-r11187 (that
utilizes that new syscall) is very confused. The fix has been tested with
that eglibc version.
Signed-off-by: Bernhard Walle <walle@corscience.de>
To: linux-mips@linux-mips.org
Cc: ddaney@caviumnetworks.com
Cc: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1567/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

These would result in KERN_<level> actually getting printed.
Signed-off-by: Joe Perches <joe@perches.com>
To: Jiri Kosina <trivial@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1581/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

No rubbish printks - those belong to userspace.  The halt function now
actually halts the system and the poweroff function was deleted because
it didn't actually power down the system.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

This prevents the GIC code from being reusable sanely.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Only VSMP was known as SMVP and generally the help text was too short to
be helpful.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

This only matters for ISA devices with a 24-bit DMA limit or for devices
with a 32-bit DMA limit on systems with ZONE_DMA32 enabled.  The latter
currently only affects 32-bit PCI cards on Sibyte-based systems with more
than 1GB RAM installed.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>