* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  fix spinlock recursion in hvc_console
  stop_machine: remove unused variable
  modules: extend initcall_debug functionality to the module loader
  export virtio_rng.h
  lguest: use get_user_pages_fast() instead of get_user_pages()
  mm: Make generic weak get_user_pages_fast and EXPORT_GPL it
  lguest: don't set MAC address for guest unless specified

* 'agp-patches' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/agp-2.6:
  agp: fix SIS 5591/5592 wrong PCI id
  intel/agp: rewrite GTT on resume
  agp: use dev_printk when possible
  amd64-agp: run fallback when no bridges found, not when driver registration fails
  intel_agp: official name for GM45 chipset

commit 611e097d
Author: Christian Borntraeger <borntraeger@de.ibm.com>
hvc_console: rework setup to replace irq functions with callbacks
introduced a spinlock recursion problem.

request_irq tries to call the handler if the IRQ is shared.
The irq handler of hvc_console calls hvc_poll and hvc_kill
which might take the hvc_struct spinlock. Therefore, we have
to call request_irq outside the spinlock.

We can move the notifier_add safely outside the spinlock as ->data must
not be changed by the backend. Otherwise, tty_hangup would fail anyway.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

The kernel has this really nice facility where if you put "initcall_debug"
on the kernel commandline, it'll print which function it's going to
execute just before calling an initcall, and then after the call completes
it will

1) print if it had an error code

2) checks for a few simple bugs (like leaving irqs off)
and

3) print how long the init call took in milliseconds.

While trying to optimize the boot speed of my laptop, I have been loving
number 3 to figure out what to optimize...  ...  and then I wished that
the same thing was done for module loading.

This patch makes the module loader use this exact same functionality; it's
a logical extension in my view (since modules are just sort of late
binding initcalls anyway) and so far I've found it quite useful in finding
where things are too slow in my boot.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Hello Rusty,

The entropy device was added after we exported all virtio headers. This
patch adds virtio_rng.h to the exportable userspace headers.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Using a simple page table thrashing program I measure a slight
improvement.  The program creates five processes.  Each touches 1000
pages then schedules the next process.  We repeat this 1000 times.  As
lguest only caches 4 cr3 values, this rebuilds a lot of shadow page
tables requiring virt->phys mappings.

	Before: 5.93 seconds
	After: 5.40 seconds

(Counts of slow vs fastpath in this usage are 6092 and 2852462 respectively.)

And more importantly for lguest, the code is simpler.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Out of line get_user_pages_fast fallback implementation, make it a weak
symbol, get rid of CONFIG_HAVE_GET_USER_PAGES_FAST.

Export the symbol to modules so lguest can use it.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This shows up when trying to bridge:
	tap0: received packet with  own address as source address

As Max Krasnyansky points out, there's no reason to give the guest the
same mac address as the TUN device.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Max Krasnyansky <maxk@qualcomm.com>

The correct id is the id of the main host (5591) not
the id of the PCI-to-PCI bridge AGP (0001).
Output from "lspci -nv" shows that only the former
has AGP capabilities flag set:

00:00.0 0600: 1039:5591 (rev 02)
        Flags: bus master, medium devsel, latency 64
        Memory at ec000000 (32-bit, non-prefetchable) [size=32M]
        Capabilities: [c0] AGP version 1.0

00:02.0 0604: 1039:0001 (prog-if 00 [Normal decode])
        Flags: bus master, fast devsel, latency 0
        Bus: primary=00, secondary=01, subordinate=01, sec-latency=0
        I/O behind bridge: 0000c000-0000cfff
        Memory behind bridge: eb500000-eb5fffff
        Prefetchable memory behind bridge: eb300000-eb3fffff
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Dave Airlie <airlied@redhat.com>

On my Intel chipset (965GM), the GTT is entirely erased across
suspend/resume.  This patch simply re-plays the current mapping at resume
time to restore the table.=20

I noticed this once I started relying on persistent GTT mappings across VT
switch in our GEM work -- the old X server and DRM code carefully unbind
all memory from the GTT on VT switch, but GEM does not bother.

I placed the list management and rewrite code in the generic layer on the
assumption that it will be needed on other hardware, but I did not add the
rewrite call to anything other than the Intel resume function.

Keep a list of current GATT mappings.  At resume time, rewrite them into
the GATT.  This is needed on Intel (at least) as the entire GATT is
cleared across suspend/resume.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Keith Packard <keithp@keithp.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Convert printks to use dev_printk().
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

I think the intent was that if no bridges matched agp_amd64_pci_table[],
we would fall back to checking for any bridge with the AGP capability.
But in the current code, we execute the fallback path only when
pci_register_driver() itself fails, which is unrelated to whether any
matching devices were found.

This patch counts the AGP bridges found in the probe() method and executes
the fallback path when none is found.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Signed-off-by: Zhenyu Wang <zhenyu.z.wang@intel.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

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

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched, cpu hotplug: fix set_cpus_allowed() use in hotplug callbacks
  sched: fix mysql+oltp regression
  sched_clock: delay using sched_clock()
  sched clock: couple local and remote clocks
  sched clock: simplify __update_sched_clock()
  sched: eliminate scd->prev_raw
  sched clock: clean up sched_clock_cpu()
  sched clock: revert various sched_clock() changes
  sched: move sched_clock before first use
  sched: test runtime rather than period in global_rt_runtime()
  sched: fix SCHED_HRTICK dependency
  sched: fix warning in hrtick_start_fair()

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

* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  posix-timers: fix posix_timer_event() vs dequeue_signal() race
  posix-timers: do_schedule_next_timer: fix the setting of ->si_overrun

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:
  lockdep: fix debug_lock_alloc
  lockdep: increase MAX_LOCKDEP_KEYS
  generic-ipi: fix stack and rcu interaction bug in smp_call_function_mask()
  lockdep: fix overflow in the hlock shrinkage code
  lockdep: rename map_[acquire|release]() => lock_map_[acquire|release]()
  lockdep: handle chains involving classes defined in modules
  mm: fix mm_take_all_locks() locking order
  lockdep: annotate mm_take_all_locks()
  lockdep: spin_lock_nest_lock()
  lockdep: lock protection locks
  lockdep: map_acquire
  lockdep: shrink held_lock structure
  lockdep: re-annotate scheduler runqueues
  lockdep: lock_set_subclass - reset a held lock's subclass
  lockdep: change scheduler annotation
  debug_locks: set oops_in_progress if we will log messages.
  lockdep: fix combinatorial explosion in lock subgraph traversal

Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86: fix 2.6.27rc1 cannot boot more than 8CPUs
  x86: make "apic" an early_param() on 32-bit, NULL check
  EFI, x86: fix function prototype
  x86, pci-calgary: fix function declaration
  x86: work around gcc 3.4.x bug
  x86: make "apic" an early_param() on 32-bit
  x86, debug: tone down arch/x86/kernel/mpparse.c debugging printk
  x86_64: restore the proper NR_IRQS define so larger systems work.
  x86: Restore proper vector locking during cpu hotplug
  x86: Fix broken VMI in 2.6.27-rc..
  x86: fdiv bug detection fix

When we enable DEBUG_LOCK_ALLOC but do not enable PROVE_LOCKING and or
LOCK_STAT, lock_alloc() and lock_release() turn into nops, even though
we should be doing hlock checking (check=1).

This causes a false warning and a lockdep self-disable.

Rectify this.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Jeff Chua reported that booting a !bigsmp kernel on a 16-way box
hangs silently.

this is a long-standing issue, smp start AP cpu could check the
apic id >=8 etc before trying to start it.

achieve this by moving the def_to_bigsmp check later and skip the
apicid id > 8

[ mingo@elte.hu: clean up the message that is printed. ]
Reported-by: "Jeff Chua" <jeff.chua.linux@gmail.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

 arch/x86/kernel/setup.c   |    6 ------
 arch/x86/kernel/smpboot.c |   10 ++++++++++
 2 files changed, 10 insertions(+), 6 deletions(-)

This patch makes several needlessly global struct scsi_dh_devlist's
static.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

* 'for-linus' of git://git.o-hand.com/linux-mfd:
  mfd: tc6393 cleanup and update
  mfd: have TMIO drivers and subdevices depend on ARM
  mfd: TMIO MMC driver
  mfd: driver for the TMIO NAND controller
  mfd: t7l66 MMC platform data
  mfd: tc6387 MMC platform data
  mfd: Fix 7l66 and 6387 according to the new mfd-core API
  mfd: Fix tc6393 according to the new tmio.h
  mfd: driver for the TC6387XB TMIO controller.
  mfd: driver for the T7L66XB TMIO SoC
  mfd: TMIO MMC structures and accessors.

* 'i2c-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6:
  hwmon: (lm75) Drop legacy i2c driver
  i2c: correct some size_t printk formats
  i2c: Check for address business before creating clients
  i2c: Let users select algorithm drivers manually again
  i2c: Fix NULL pointer dereference in i2c_new_probed_device
  i2c: Fix oops on bus multiplexer driver loading

* git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog:
  [WATCHDOG] pcwd.c - fix open_allowed type.
  [WATCHDOG] fix watchdog/ixp4xx_wdt.c compilation
  [WATCHDOG] fix watchdog/wdt285.c compilation
  [WATCHDOG] fix watchdog/at91rm9200_wdt.c compilation
  [WATCHDOG] fix watchdog/shwdt.c compilation
  [WATCHDOG] fix watchdog/txx9wdt.c compilation
  [WATCHDOG] MAINTAINERS: remove ZF MACHZ WATCHDOG entry
  [WATCHDOG] Fix build with CONFIG_ITCO_VENDOR_SUPPORT=n

Cyrill Gorcunov observed:

> you turned it into early_param so now it's NULL injecting vulnerabled.
> Could you please add checking for NULL str param?

fix that.

Also, change the name of 'str' into 'arg', to make it more apparent
that this is an optional argument that can be NULL, not a string
parameter that is empty when unset.
Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc:
  powerpc: Remove include/linux/harrier_defs.h
  powerpc: Do not ignore arch/powerpc/include
  powerpc: Delete completed "ppc removal" task from feature removal file
  powerpc/mm: Fix attribute confusion with htab_bolt_mapping()
  powerpc/pci: Don't keep ISA memory hole resources in the tree
  powerpc: Zero fill the return values of rtas argument buffer
  powerpc/4xx: Update defconfig files for 2.6.27-rc1
  powerpc/44x: Incorrect NOR offset in Warp DTS
  powerpc/44x: Warp DTS changes for board updates
  powerpc/4xx: Cleanup Warp for i2c driver changes.
  powerpc/44x: Adjust warp-nand resource end address

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6:
  PCI: Limit VPD length for Broadcom 5708S
  PCI PM: Export pci_pme_active to drivers
  PCI: remove duplicate symbol from pci_ids.h
  PCI: check the return value of device_create_bin_file() in pci_create_bus()
  PCI: fully restore MSI state at resume time
  DMA: make dma-coherent.c documentation kdoc-friendly
  PCI: make pci_register_driver() a macro
  PCI: add Broadcom 5708S to VPD length quirk

While testing our KVM code for s390 (starting and killall kvm in a loop)
I can reproduce the following oops:

  Unable to handle kernel pointer dereference at virtual kernel address 6b6b6b6b6b6b6000 Oops: 0038 [#1] SMP
  Modules linked in: dm_multipath sunrpc qeth_l3 qeth_l2 dm_mod qeth
  ccwgroup CPU: 1 Not tainted 2.6.27-rc1 #54
  Process kuli (pid: 4409, task: 00000000b6aa5940, ksp: 00000000b7343e10)
  Krnl PSW : 0704e00180000000 00000000002e0b8c
  (disassociate_ctty+0x1c0/0x288) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3
  CC:2 PM:0 EA:3 Krnl GPRS: 0000000000000000 6b6b6b6b6b6b6b6b
  0000000000000001 00000000000003a6 00000000002e0a46 00000000004b4160
  0000000000000001 00000000bbd79758 00000000b7343e58 00000000b8854148
  00000000bd34dea0 00000000b7343c20 0000000000000001 00000000004b6d08
  00000000002e0a46 00000000b7343c20 Krnl Code: 00000000002e0b7e:
  eb9fb0a00004	lmg	%r9,%r15,160(%r11) 00000000002e0b84:
  07f4		bcr	15,%r4 00000000002e0b86:
  e31090080004	lg	%r1,8(%r9) >00000000002e0b8c:
  d501109cd000	clc	156(2,%r1),0(%r13) 00000000002e0b92:
  a784ff5d		brc	8,2e0a4c 00000000002e0b96:
  b9040029		lgr	%r2,%r9 00000000002e0b9a:
  c0e5fffff9c3	brasl	%r14,2dff20 00000000002e0ba0:
  a7f4ff56		brc	15,2e0a4c Call Trace:
  ([<00000000002e0a46>] disassociate_ctty+0x7a/0x288)
   [<0000000000141fe6>] do_exit+0x212/0x8d4
   [<0000000000142708>] do_group_exit+0x60/0xcc
   [<0000000000150660>] get_signal_to_deliver+0x270/0x3ac
   [<000000000010bfd6>] do_signal+0x8e/0x8dc
   [<0000000000113772>] sysc_sigpending+0xe/0x22
   [<000001ff0000b134>] 0x1ff0000b134
  INFO: lockdep is turned off.
  Last Breaking-Event-Address:
   [<00000000002e0a48>] disassociate_ctty+0x7c/0x288
  Kernel panic - not syncing: Fatal exception: panic_on_oops

It seems that tty was already free in disassocate_ctty when it tries
to dereference tty->driver.

After moving the lock_kernel before the mutex_unlock, I can no longer
reproduce the problem.

[ This is a temporary partial fix for the documented and long standing
  race in disassociate_tty.  This stops most problem cases for now.

  For the next release the -next tree has an initial implementation of
  kref counting for tty structures and this quickfix will be dropped.

                                                              - Alan ]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by; Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Wire up for m68k{,nommu} the system calls that were added in the last merge
window:

 - 4006553b ("flag parameters: inotify_init")
 - ed8cae8b ("flag parameters: pipe")
 - 336dd1f7 ("flag parameters: dup2")
 - a0998b50 ("flag parameters: epoll_create")
 - 9fe5ad9c ("flag parameters add-on: remove
						 epoll_create size param")
 - b087498e ("flag parameters: eventfd")
 - 9deb27ba ("flag parameters: signalfd")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This reverts commit 2d04a4a7, which made
it impossible to make the softcursor use the highlight colors.

Yes, the fourth bit should be "blinking", but since we cannot reasonably
blink in fbcon, highlighting it with a bright background is preferable.
Reported-by: Pavel Machek <pavel@suse.cz>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Antonino A. Daplas <adaplas@pol.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix function prototype in header file to match source code:

linux-next-20080807/arch/x86/kernel/efi_64.c:100:14: error: symbol 'efi_ioremap' redeclared with different type (originally declared at include2/asm/efi.h:89) - different address spaces
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Fix function declaration:

 linux-next-20080807/arch/x86/kernel/pci-calgary_64.c:1353:36: warning: non-ANSI function declaration of function 'get_tce_space_from_tar'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Acked-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Simon Horman reported that gcc-3.4.x crashes when compiling
pgd_prepopulate_pmd() when PREALLOCATED_PMDS == 0 and CONFIG_DEBUG_INFO
is enabled.

Adding an extra check for PREALLOCATED_PMDS == 0 [which is compiled out
by gcc] seems to avoid the problem.
Reported-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

On 32-bit, "apic" is a __setup() param meaning it is parsed rather
late in the game. Make it an early_param() for apic_printk() use
by arch/x86/kernel/mpparse.c.

On 64-bit, it already is an early_param().
Signed-off-by: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

commit 11a62a05 turns some formerly
nopped debugging printks in arch/x86/kernel/mppparse.c into regular
ones. The one at the top of smp_scan_config() in particular also
prints on !CONFIG_SMP/CONFIG_X86_LOCAL_APIC kernels and UP machines
without anything resembling MP tables which makes their lowly UP
owners wonder...

Turn the former Dprintk()s into apic_printk()s instead meaning that
their printing is dependent on passing the apic=verbose (or =debug)
command line param.

On 32-bit, "apic" is a __setup() param which isn't early enough
for this code and therefore needs a followup changing it into an
early_param(). On 64-bit, it already is.
Signed-off-by: Rene Herman <rene.herman@gmail.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Mark Langsdorf reported:

> One of my co-workers noticed that the powernow-k8
> driver no longer restarts when a CPU core is
> hot-disabled and then hot-enabled on AMD quad-core
> systems.
>
> The following comands work fine on 2.6.26 and fail
> on 2.6.27-rc1:
>
> echo 0 > /sys/devices/system/cpu/cpu3/online
> echo 1 > /sys/devices/system/cpu/cpu3/online
> find /sys -name cpufreq
>
> For 2.6.26, the find will return a cpufreq
> directory for each processor.  In 2.6.27-rc1,
> the cpu3 directory is missing.
>
> After digging through the code, the following
> logic is failing when the core is hot-enabled
> at runtime.  The code works during the boot
> sequence.
>
>       cpumask_t = current->cpus_allowed;
>       set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
>       if (smp_processor_id() != cpu)
>               return -ENODEV;

So set the CPU active before calling the CPU_ONLINE notifier chain,
there are a handful of notifiers that use set_cpus_allowed().

This fix also solves the problem with x86-microcode. I've sent
alternative patches for microcode, but as this "rely on
set_cpus_allowed_ptr() being workable in cpu-hotplug(CPU_ONLINE, ...)"
assumption seems to be more broad than what we thought, perhaps this fix
should be applied.

With this patch we define that by the moment CPU_ONLINE is being sent,
a 'cpu' is online and ready for tasks to be migrated onto it.
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Reported-by: Mark Langsdorf <mark.langsdorf@amd.com>
Tested-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

certain configs produce:

 [   70.076229] BUG: MAX_LOCKDEP_KEYS too low!
 [   70.080230] turning off the locking correctness validator.

tune them up.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

* Venki Pallipadi <venkatesh.pallipadi@intel.com> wrote:

> Found a OOPS on a big SMP box during an overnight reboot test with
> upstream git.
>
> Suresh and I looked at the oops and looks like the root cause is in
> generic_smp_call_function_interrupt() and smp_call_function_mask() with
> wait parameter.
>
> The actual oops looked like
>
> [   11.277260] BUG: unable to handle kernel paging request at ffff8802ffffffff
> [   11.277815] IP: [<ffff8802ffffffff>] 0xffff8802ffffffff
> [   11.278155] PGD 202063 PUD 0
> [   11.278576] Oops: 0010 [1] SMP
> [   11.279006] CPU 5
> [   11.279336] Modules linked in:
> [   11.279752] Pid: 0, comm: swapper Not tainted 2.6.27-rc2-00020-g685d87f7 #290
> [   11.280039] RIP: 0010:[<ffff8802ffffffff>]  [<ffff8802ffffffff>] 0xffff8802ffffffff
> [   11.280692] RSP: 0018:ffff88027f1f7f70  EFLAGS: 00010086
> [   11.280976] RAX: 00000000ffffffff RBX: 0000000000000000 RCX: 0000000000000000
> [   11.281264] RDX: 0000000000004f4e RSI: 0000000000000001 RDI: 0000000000000000
> [   11.281624] RBP: ffff88027f1f7f98 R08: 0000000000000001 R09: ffffffff802509af
> [   11.281925] R10: ffff8800280c2780 R11: 0000000000000000 R12: ffff88027f097d48
> [   11.282214] R13: ffff88027f097d70 R14: 0000000000000005 R15: ffff88027e571000
> [   11.282502] FS:  0000000000000000(0000) GS:ffff88027f1c3340(0000) knlGS:0000000000000000
> [   11.283096] CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> [   11.283382] CR2: ffff8802ffffffff CR3: 0000000000201000 CR4: 00000000000006e0
> [   11.283760] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   11.284048] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [   11.284337] Process swapper (pid: 0, threadinfo ffff88027f1f2000, task ffff88027f1f0640)
> [   11.284936] Stack:  ffffffff80250963 0000000000000212 0000000000ee8c78 0000000000ee8a66
> [   11.285802]  ffff88027e571550 ffff88027f1f7fa8 ffffffff8021adb5 ffff88027f1f3e40
> [   11.286599]  ffffffff8020bdd6 ffff88027f1f3e40 <EOI>  ffff88027f1f3ef8 0000000000000000
> [   11.287120] Call Trace:
> [   11.287768]  <IRQ>  [<ffffffff80250963>] ? generic_smp_call_function_interrupt+0x61/0x12c
> [   11.288354]  [<ffffffff8021adb5>] smp_call_function_interrupt+0x17/0x27
> [   11.288744]  [<ffffffff8020bdd6>] call_function_interrupt+0x66/0x70
> [   11.289030]  <EOI>  [<ffffffff8024ab3b>] ? clockevents_notify+0x19/0x73
> [   11.289380]  [<ffffffff803b9b75>] ? acpi_idle_enter_simple+0x18b/0x1fa
> [   11.289760]  [<ffffffff803b9b6b>] ? acpi_idle_enter_simple+0x181/0x1fa
> [   11.290051]  [<ffffffff8053aeca>] ? cpuidle_idle_call+0x70/0xa2
> [   11.290338]  [<ffffffff80209f61>] ? cpu_idle+0x5f/0x7d
> [   11.290723]  [<ffffffff8060224a>] ? start_secondary+0x14d/0x152
> [   11.291010]
> [   11.291287]
> [   11.291654] Code:  Bad RIP value.
> [   11.292041] RIP  [<ffff8802ffffffff>] 0xffff8802ffffffff
> [   11.292380]  RSP <ffff88027f1f7f70>
> [   11.292741] CR2: ffff8802ffffffff
> [   11.310951] ---[ end trace 137c54d525305f1c ]---
>
> The problem is with the following sequence of events:
>
> - CPU A calls smp_call_function_mask() for CPU B with wait parameter
> - CPU A sets up the call_function_data on the stack and does an rcu add to
>   call_function_queue
> - CPU A waits until the WAIT flag is cleared
> - CPU B gets the call function interrupt and starts going through the
>   call_function_queue
> - CPU C also gets some other call function interrupt and starts going through
>   the call_function_queue
> - CPU C, which is also going through the call_function_queue, starts referencing
>   CPU A's stack, as that element is still in call_function_queue
> - CPU B finishes the function call that CPU A set up and as there are no other
>   references to it, rcu deletes the call_function_data (which was from CPU A
>   stack)
> - CPU B sees the wait flag and just clears the flag (no call_rcu to free)
> - CPU A which was waiting on the flag continues executing and the stack
>   contents change
>
> - CPU C is still in rcu_read section accessing the CPU A's stack sees
>   inconsistent call_funation_data and can try to execute
>   function with some random pointer, causing stack corruption for A
>   (by clearing the bits in mask field) and oops.

Nice debugging work.

I'd suggest something like the attached (boot tested) patch as the simple
fix for now.

I expect the benefits from the less synchronized, multiple-in-flight-data
global queue will still outweigh the costs of dynamic allocations. But
if worst comes to worst then we just go back to a globally synchronous
one-at-a-time implementation, but that would be pretty sad!
Signed-off-by: Ingo Molnar <mingo@elte.hu>