I am seeing an issue where a CPU running perf eventually hangs.
Traces show timer interrupts happening every 4 seconds even
when a userspace task is running on the CPU. /proc/timer_list
also shows pending hrtimers have not run in over an hour,
including the scheduler.

Looking closer, decrementers_next_tb is getting set to
0xffffffffffffffff, and at that point we will never take
a timer interrupt again.

In __timer_interrupt() we set decrementers_next_tb to
0xffffffffffffffff and rely on ->event_handler to update it:

        *next_tb = ~(u64)0;
        if (evt->event_handler)
                evt->event_handler(evt);

In this case ->event_handler is hrtimer_interrupt. This will eventually
call back through the clockevents code with the next event to be
programmed:

static int decrementer_set_next_event(unsigned long evt,
                                      struct clock_event_device *dev)
{
        /* Don't adjust the decrementer if some irq work is pending */
        if (test_irq_work_pending())
                return 0;
        __get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;

If irq work came in between these two points, we will return
before updating decrementers_next_tb and we never process a timer
interrupt again.

This looks to have been introduced by 0215f7d8c53f (powerpc: Fix races
with irq_work). Fix it by removing the early exit and relying on
code later on in the function to force an early decrementer:

       /* We may have raced with new irq work */
       if (test_irq_work_pending())
               set_dec(1);

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

module_init should return 0 or a negative errno.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Commit aac416fc38c (lkdtm: flush icache and report actions) calls
flush_icache_range from a module. It's exported on most architectures
that implement it, but not on powerpc. This patch exports it to fix
the module link failure.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3bc955987fb3 ("powerpc/PCI: Use list_for_each_entry() for bus traversal")
caused a NULL pointer dereference because the loop body set the iterator to
NULL:

  Unable to handle kernel paging request for data at address 0x00000000
  Faulting instruction address: 0xc000000000041d78
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP [c000000000041d78] .sys_pciconfig_iobase+0x68/0x1f0
  LR [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0
  Call Trace:
  [c0000003b4787db0] [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0 (unreliable)
  [c0000003b4787e30] [c000000000009ed8] syscall_exit+0x0/0x98

Fix it by using a temporary variable for the iterator.

[bhelgaas: changelog, drop tmp_bus initialization]
Fixes: 3bc955987fb3 powerpc/PCI: Use list_for_each_entry() for bus traversal
Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Commit 8f619b5429d9 ("powerpc/ppc64: Do not turn AIL (reloc-on
interrupts) too early") added code to set the AIL bit in the LPCR
without checking whether the kernel is running in hypervisor mode.  The
result is that when the kernel is running as a guest (i.e., under
PowerKVM or PowerVM), the processor takes a privileged instruction
interrupt at that point, causing a panic.  The visible result is that
the kernel hangs after printing "returning from prom_init".

This fixes it by checking for hypervisor mode being available before
setting LPCR.  If we are not in hypervisor mode, we enable relocation-on
interrupts later in pSeries_setup_arch using the H_SET_MODE hcall.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull more powerpc updates from Ben Herrenschmidt:
 "Here are a few more powerpc things for you.

  So you'll find here the conversion of the two new firmware sysfs
  interfaces to the new API for self-removing files that Greg and Tejun
  introduced, so they can finally remove the old one.

  I'm also reverting the hwmon driver for powernv.  I shouldn't have
  merged it, I got a bit carried away here.  I hadn't realized it was
  never CCed to the relevant maintainer(s) and list(s), and happens to
  have some issues so I'm taking it out and it will come back via the
  proper channels.

  The rest is a bunch of LE fixes (argh, some of the new stuff was
  broken on LE, I really need to start testing LE myself !) and various
  random fixes here and there.

  Finally one bit that's not strictly a fix, which is the HVC OPAL
  change to "kick" the HVC thread when the firmware tells us there is
  new incoming data.  I don't feel like waiting for this one, it's
  simple enough, and it makes a big difference in console responsiveness
  which is good for my nerves"

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: (26 commits)
  powerpc/powernv Adapt opal-elog and opal-dump to new sysfs_remove_file_self
  Revert "powerpc/powernv: hwmon driver for power values, fan rpm and temperature"
  power, sched: stop updating inside arch_update_cpu_topology() when nothing to be update
  powerpc/le: Avoid creatng R_PPC64_TOCSAVE relocations for modules.
  arch/powerpc: Use RCU_INIT_POINTER(x, NULL) in platforms/cell/spu_syscalls.c
  powerpc/opal: Add missing include
  powerpc: Convert last uses of __FUNCTION__ to __func__
  powerpc: Add lq/stq emulation
  powerpc/powernv: Add invalid OPAL call
  powerpc/powernv: Add OPAL message log interface
  powerpc/book3s: Fix mc_recoverable_range buffer overrun issue.
  powerpc: Remove dead code in sycall entry
  powerpc: Use of_node_init() for the fakenode in msi_bitmap.c
  powerpc/mm: NUMA pte should be handled via slow path in get_user_pages_fast()
  powerpc/powernv: Fix endian issues with sensor code
  powerpc/powernv: Fix endian issues with OPAL async code
  tty/hvc_opal: Kick the HVC thread on OPAL console events
  powerpc/powernv: Add opal_notifier_unregister() and export to modules
  powerpc/ppc64: Do not turn AIL (reloc-on interrupts) too early
  powerpc/ppc64: Gracefully handle early interrupts
  ...

Recent CPUs support quad word load and store instructions. Add
support to the alignment handler for them.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

In:
  commit 742415d6b66bf09e3e73280178ef7ec85c90b7ee
  Author: Michael Neuling <mikey@neuling.org>
  powerpc: Turn syscall handler into macros

We converted the syscall entry code onto macros, but in doing this we
introduced some cruft that's never run and should never have been added.

This removes that code.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Pull CPU hotplug notifiers registration fixes from Rafael Wysocki:
 "The purpose of this single series of commits from Srivatsa S Bhat
  (with a small piece from Gautham R Shenoy) touching multiple
  subsystems that use CPU hotplug notifiers is to provide a way to
  register them that will not lead to deadlocks with CPU online/offline
  operations as described in the changelog of commit 93ae4f978ca7f ("CPU
  hotplug: Provide lockless versions of callback registration
  functions").

  The first three commits in the series introduce the API and document
  it and the rest simply goes through the users of CPU hotplug notifiers
  and converts them to using the new method"

* tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (52 commits)
  net/iucv/iucv.c: Fix CPU hotplug callback registration
  net/core/flow.c: Fix CPU hotplug callback registration
  mm, zswap: Fix CPU hotplug callback registration
  mm, vmstat: Fix CPU hotplug callback registration
  profile: Fix CPU hotplug callback registration
  trace, ring-buffer: Fix CPU hotplug callback registration
  xen, balloon: Fix CPU hotplug callback registration
  hwmon, via-cputemp: Fix CPU hotplug callback registration
  hwmon, coretemp: Fix CPU hotplug callback registration
  thermal, x86-pkg-temp: Fix CPU hotplug callback registration
  octeon, watchdog: Fix CPU hotplug callback registration
  oprofile, nmi-timer: Fix CPU hotplug callback registration
  intel-idle: Fix CPU hotplug callback registration
  clocksource, dummy-timer: Fix CPU hotplug callback registration
  drivers/base/topology.c: Fix CPU hotplug callback registration
  acpi-cpufreq: Fix CPU hotplug callback registration
  zsmalloc: Fix CPU hotplug callback registration
  scsi, fcoe: Fix CPU hotplug callback registration
  scsi, bnx2fc: Fix CPU hotplug callback registration
  scsi, bnx2i: Fix CPU hotplug callback registration
  ...

Turn them on at the same time as we allow MSR_IR/DR in the paca
kernel MSR, ie, after the MMU has been setup enough to be able
to handle relocated access to the linear mapping.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>