Allows perf to clean up properly on exit.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1346005487-62961-6-git-send-email-dsahern@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Allows perf to clean up properly on program termination.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1346005487-62961-5-git-send-email-dsahern@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Allows perf to clean up properly on exit.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1346005487-62961-4-git-send-email-dsahern@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Handle error from process callback and propagate back to caller.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1346005487-62961-3-git-send-email-dsahern@gmail.comSigned-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Allows errors to propogate through event processing code and back to
commands.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1346005487-62961-2-git-send-email-dsahern@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Replace keyword "private" to "priv" in event-parse.h to allow it to be
used in C++ programs.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1345735321.5069.62.camel@gandalf.local.homeSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Pull oprofile fixes from Robert Richter.
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Nobody does set_orig_insn(verify => false), and I think nobody will.
Remove this argument. IIUC set_orig_insn(verify => false) was needed
to single-step without xol area.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Now that we have uprobe_dup_mmap() we can fold uprobe_reset_state()
into the new hook and remove it. mmput()->uprobe_clear_state() can't
be called before dup_mmap().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Add the new MMF_HAS_UPROBES flag. It is set by install_breakpoint()
and it is copied by dup_mmap(), uprobe_pre_sstep_notifier() checks
it to avoid the slow path if the task was never probed. Perhaps it
makes sense to check it in valid_vma(is_register => false) as well.

This needs the new dup_mmap()->uprobe_dup_mmap() hook. We can't use
uprobe_reset_state() or put MMF_HAS_UPROBES into MMF_INIT_MASK, we
need oldmm->mmap_sem to avoid the race with uprobe_register() or
mmap() from another thread.

Currently we never clear this bit, it can be false-positive after
uprobe_unregister() or uprobe_munmap() or if dup_mmap() hits the
probed VM_DONTCOPY vma. But this is fine correctness-wise and has
no effect unless the task hits the non-uprobe breakpoint.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

-EEXIST from install_breakpoint() no longer makes sense, all
callers should simply treat it as "success". Change the code
to return zero and simplify register_for_each_vma().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Once install_breakpoint() fails uprobe_mmap() "ignores" all other
uprobes and returns the error.

It was never really needed to to stop after the first error, and
in fact it was always wrong at least in -ENOTSUPP case.

Change uprobe_mmap() to ignore the errors and always return 0.
This is not what we want in the long term, but until we teach
the callers to handle the failure it would be better to remove
the pointless complications. And this doesn't look too bad, the
only "reasonable" error is ENOMEM but in this case the caller
should be oom-killed in the likely case or the system has more
serious problems.

However it makes sense to stop if fatal_signal_pending() == T.
In particular this helps if the task was oom-killed.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

1. Kill dup_mmap()->uprobe_mmap(), it was only needed to calculate
   new_mm->uprobes_state.count removed by the previous patch.

   If the forking process has a pending uprobe (int3) in vma, it will
   be copied by copy_page_range(), note that it checks vma->anon_vma
   so "Don't copy ptes" is not possible after install_breakpoint()
   which does anon_vma_prepare().

2. Remove is_swbp_at_addr() and "int count" in uprobe_mmap(). Again,
   this was needed for uprobes_state.count.

   As a side effect this fixes the bug pointed out by Srikar,
   this code lacked the necessary put_uprobe().

3. uprobe_munmap() becomes a nop after the previous patch. Remove the
   meaningless code but do not remove the helper, we will need it.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

uprobes_state->count is only needed to avoid the slow path in
uprobe_pre_sstep_notifier(). It is also checked in uprobe_munmap()
but ironically its only goal to decrement this counter. However,
it is very broken. Just some examples:

- uprobe_mmap() can race with uprobe_unregister() and wrongly
  increment the counter if it hits the non-uprobe "int3". Note
  that install_breakpoint() checks ->consumers first and returns
  -EEXIST if it is NULL.

  "atomic_sub() if error" in uprobe_mmap() looks obviously wrong
  too.

- uprobe_munmap() can race with uprobe_register() and wrongly
  decrement the counter by the same reason.

- Suppose an appication tries to increase the mmapped area via
  sys_mremap(). vma_adjust() does uprobe_munmap(whole_vma) first,
  this can nullify the counter temporarily and race with another
  thread which can hit the bp, the application will be killed by
  SIGTRAP.

- Suppose an application mmaps 2 consecutive areas in the same file
  and one (or both) of these areas has uprobes. In the likely case
  mmap_region()->vma_merge() suceeds. Like above, this leads to
  uprobe_munmap/uprobe_mmap from vma_merge()->vma_adjust() but then
  mmap_region() does another uprobe_mmap(resulting_vma) and doubles
  the counter.

This patch only removes this counter and fixes the compile errors,
then we will try to cleanup the changed code and add something else
instead.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

by the time we get here (after we pass cleanup_ret) uprobe is always is
set. If it is NULL we leave very early in the code.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Since read_opcode() reads from the referenced page and doesnt modify
the page contents nor the page attributes, there is no need to lock
the page.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Pick up the latest fixes because upcoming uprobes changes will rely on it.
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Under certain workloads we see the following warnings:

 WQ on CPU0, prefer CPU1
 WQ on CPU0, prefer CPU2
 WQ on CPU0, prefer CPU3

It warns the user that the wq to access a per-cpu buffers runs not on
the same cpu. This happens if the wq is rescheduled on a different cpu
than where the buffer is located. This was probably implemented to
detect performance issues. Not sure if there actually is one as the
buffers are copied to a single buffer anyway which should be the
actual bottleneck.

We wont change WQ implementation. Since a user can do nothing the
warning is pointless. Removing it.

Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>

If oprofilefs_ulong_from_user() is called with count equals zero, *val
remains unchanged. Depending on the implementation it might be
uninitialized. Fixing users of oprofilefs_ulong_ from_user().

We missed these s390 changes with:

 913050b9 oprofile: Fix uninitialized memory access when writing to writing to oprofilefs

Cc: stable@vger.kernel.org  # 3.3+
Signed-off-by: Robert Richter <robert.richter@amd.com>

The following patch makes the microcode update code path
actually invoke the perf_check_microcode() function and
thus potentially renabling SNB PEBS.

By default, CONFIG_MICROCODE_OLD_INTERFACE is
forced to Y in arch/x86/Kconfig. There is no
way to disable this. That means that the code
path used in arch/x86/kernel/microcode_core.c
did not include the call to perf_check_microcode().

Thus, even though the microcode was updated to a
version that fixes the SNB PEBS problem, perf_event
would still return EOPNOTSUPP when enabling precise
sampling.

This patch simply adds a call to perf_check_microcode()
in the call path used when OLD_INTERFACE=y.
Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: peterz@infradead.org
Cc: andi@firstfloor.org
Link: http://lkml.kernel.org/r/20120824133434.GA8014@quadSigned-off-by: Ingo Molnar <mingo@kernel.org>

Pull arm-soc fixes from Arnd Bergmann:
 "Bug fixes for various ARM platforms.  About half of these are for OMAP
  and submitted before but did not make it into v3.6-rc2."

* tag 'fixes-3.6-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (39 commits)
  ARM: ux500: don't select LEDS_GPIO for snowball
  ARM: imx: build i.MX6 functions only when needed
  ARM: imx: select CPU_FREQ_TABLE when needed
  ARM: imx: fix ksz9021rn_phy_fixup
  ARM: imx: build pm-imx5 code only when PM is enabled
  ARM: omap: allow building omap44xx without SMP
  ARM: dts: imx51-babbage: fix esdhc cd/wp properties
  ARM: imx6: spin the cpu until hardware takes it down
  ARM: ux500: Ensure probing of Audio devices when Device Tree is enabled
  ARM: ux500: Fix merge error, no matching driver name for 'snd_soc_u8500'
  ARM i.MX6q: Add virtual 1/3.5 dividers in the LDB clock path
  ARM: Kirkwood: fix Makefile.boot
  ARM: Kirkwood: Fix iconnect leds
  ARM: Orion: Set eth packet size csum offload limit
  ARM: mv78xx0: fix win_cfg_base prototype
  ARM: OMAP: dmtimers: Fix locking issue in omap_dm_timer_request*()
  ARM: mmp: fix potential NULL dereference
  ARM: OMAP4: Register the OPP table only for 4430 device
  cpufreq: OMAP: Handle missing frequency table on SMP systems
  ARM: OMAP4: sleep: Save the complete used register stack frame
  ...

Merge tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull three xen bug-fixes from Konrad Rzeszutek Wilk:
 - Revert the kexec fix which caused on non-kexec shutdowns a race.
 - Reuse existing P2M leafs - instead of requiring to allocate a large
   area of bootup virtual address estate.
 - Fix a one-off error when adding PFNs for balloon pages.

* tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/setup: Fix one-off error when adding for-balloon PFNs to the P2M.
  xen/p2m: Reuse existing P2M leafs if they are filled with 1:1 PFNs or INVALID.
  Revert "xen PVonHVM: move shared_info to MMIO before kexec"

Pull powerpc fixes from Benjamin Herrenschmidt:
 "I meant to sent that earlier but got swamped with other things, so
  here are some powerpc fixes for 3.6.  A few regression fixes and some
  bug fixes that I deemed should still make it.

  There's a FSL update from Kumar with a bunch of defconfig updates
  along with a few embedded fixes.

  I also reverted my g5_defconfig update that I merged earlier as it was
  completely busted, not too sure what happened there, I'll do a new one
  later."

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  Revert "powerpc: Update g5_defconfig"
  powerpc/perf: Use pmc_overflow() to detect rolled back events
  powerpc: Fix VMX in interrupt check in POWER7 copy loops
  powerpc: POWER7 copy_to_user/copy_from_user patch applied twice
  powerpc: Fix personality handling in ppc64_personality()
  powerpc/dma-iommu: Fix IOMMU window check
  powerpc: Remove unnecessary ifdefs
  powerpc/kgdb: Restore current_thread_info properly
  powerpc/kgdb: Bail out of KGDB when we've been triggered
  powerpc/kgdb: Do not set kgdb_single_step on ppc
  powerpc/mpic_msgr: Add missing includes
  powerpc: Fix null pointer deref in perf hardware breakpoints
  powerpc: Fixup whitespace in xmon
  powerpc: Fix xmon dl command for new printk implementation
  powerpc/fsl: fix "Failed to mount /dev: No such device" errors
  powerpc/fsl: update defconfigs
  booke/wdt: some ioctls do not return values properly
  powerpc/p4080ds: dts - add usb controller version info and port0
  powerpc/85xx: mpc85xx_defconfig - add VIA PATA support for MPC85xxCDS
  powerpc/fsl-pci: Only scan PCI bus if configured as a host

Pull kvm fixes from Marcelo Tosatti.

* git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: x86 emulator: use stack size attribute to mask rsp in stack ops
  KVM: MMU: Fix mmu_shrink() so that it can free mmu pages as intended
  ppc: e500_tlb memset clears nothing
  KVM: PPC: Add cache flush on page map
  KVM: PPC: Book3S HV: Fix incorrect branch in H_CEDE code
  KVM: x86: update KVM_SAVE_MSRS_BEGIN to correct value

Pull xfs bugfixes from Ben Myers:
 - fix uninitialised variable in xfs_rtbuf_get()
 - unlock the AGI buffer when looping in xfs_dialloc
 - check for possible overflow in xfs_ioc_trim

* tag 'for-linus-v3.6-rc4' of git://oss.sgi.com/xfs/xfs:
  xfs: check for possible overflow in xfs_ioc_trim
  xfs: unlock the AGI buffer when looping in xfs_dialloc
  xfs: fix uninitialised variable in xfs_rtbuf_get()

Pull MIPS fixes from Ralf Baechle:
 "Random fixes across the MIPS tree.  The two hotspots are several bugs
  in the module loader and the ath79 SOC support; also noteworthy is the
  restructuring of the code to synchronize CPU timers across CPUs on
  startup; the old code recently ceased to work due to unrelated
  changes.

  All except one of these patches have sat for a significant time in
  linux-next for testing."

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  MIPS: pci-ar724x: avoid data bus error due to a missing PCIe module
  MIPS: Malta: Delete duplicate PCI fixup.
  MIPS: ath79: don't hardcode the unavailability of the DSP ASE
  MIPS: Synchronize MIPS count one CPU at a time
  MIPS: BCM63xx: Fix SPI message control register handling for BCM6338/6348.
  MIPS: Module: Deal with malformed HI16/LO16 relocation sequences.
  MIPS: Fix race condition in module relocation code.
  MIPS: Fix memory leak in error path of HI16/LO16 relocation handling.
  MIPS: MTX-1: Add udelay to mtx1_pci_idsel
  MIPS: ath79: select HAVE_CLK
  MIPS: ath79: Use correct IRQ number for the OHCI controller on AR7240
  MIPS: ath79: Fix number of GPIO lines for AR724[12]
  MIPS: Octeon: Fix broken interrupt controller code.

Pull nfsd bugfixes from J. Bruce Fields:
 "Particular thanks to Michael Tokarev, Malahal Naineni, and Jamie
  Heilman for their testing and debugging help."

* 'for-3.6' of git://linux-nfs.org/~bfields/linux:
  svcrpc: fix svc_xprt_enqueue/svc_recv busy-looping
  svcrpc: sends on closed socket should stop immediately
  svcrpc: fix BUG() in svc_tcp_clear_pages
  nfsd4: fix security flavor of NFSv4.0 callback

Pull block-related fixes from Jens Axboe:

 - Improvements to the buffered and direct write IO plugging from
   Fengguang.

 - Abstract out the mapping of a bio in a request, and use that to
   provide a blk_bio_map_sg() helper.  Useful for mapping just a bio
   instead of a full request.

 - Regression fix from Hugh, fixing up a patch that went into the
   previous release cycle (and marked stable, too) attempting to prevent
   a loop in __getblk_slow().

 - Updates to discard requests, fixing up the sizing and how we align
   them.  Also a change to disallow merging of discard requests, since
   that doesn't really work properly yet.

 - A few drbd fixes.

 - Documentation updates.

* 'for-linus' of git://git.kernel.dk/linux-block:
  block: replace __getblk_slow misfix by grow_dev_page fix
  drbd: Write all pages of the bitmap after an online resize
  drbd: Finish requests that completed while IO was frozen
  drbd: fix drbd wire compatibility for empty flushes
  Documentation: update tunable options in block/cfq-iosched.txt
  Documentation: update tunable options in block/cfq-iosched.txt
  Documentation: update missing index files in block/00-INDEX
  block: move down direct IO plugging
  block: remove plugging at buffered write time
  block: disable discard request merge temporarily
  bio: Fix potential memory leak in bio_find_or_create_slab()
  block: Don't use static to define "void *p" in show_partition_start()
  block: Add blk_bio_map_sg() helper
  block: Introduce __blk_segment_map_sg() helper
  fs/block-dev.c:fix performance regression in O_DIRECT writes to md block devices
  block: split discard into aligned requests
  block: reorganize rounding of max_discard_sectors

Pull libata fixes from Jeff Garzik:
 - libata-acpi regression fix
 - additional or corrected drive quirks for ata_blacklist
 - Kconfig text tweaking
 - new PCI IDs
 - pata_atiixp: quirk for MSI motherboard
 - export ahci_dev_classify for an ahci_platform driver

* tag 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev:
  libata: Add a space to " 2GB ATA Flash Disk" DMA blacklist entry
  [libata] new quirk, lift bridge limits for Buffalo DriveStation Quattro
  [libata] Kconfig: Elaborate that SFF is meant for legacy and PATA stuff
  [libata] acpi: call ata_acpi_gtm during ata port init time
  ata_piix: Add Device IDs for Intel Lynx Point-LP PCH
  ahci: Add Device IDs for Intel Lynx Point-LP PCH
  pata_atiixp: override cable detection on MSI E350DM-E33
  ahci: un-staticize ahci_dev_classify

commit d70e551c, Add " 2GB ATA Flash
Disk"/"ADMA428M" to DMA blacklist, should have added a space before 2GB.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

This reverts commit b1acf1bb.

Something went horribly wrong when I did savedefconfig, not sure what,
but what's in there is busted so let's revert it.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

For certain speculative events on Power7, 'perf stat' reports far higher
event count than 'perf record' for the same event.

As described in following commit, a performance monitor exception is raised
even when the the performance events are rolled back.

        commit 0837e324
        Author: Anton Blanchard <anton@samba.org>
        Date:   Wed Mar 9 14:38:42 2011 +1100

perf_event_interrupt() records an event only when an overflow occurs. But
this check for overflow is a simple 'if (val < 0)'.

Because the events are rolled back, this check for overflow fails and the
event is not recorded. perf_event_interrupt() later uses pmc_overflow() to
detect the overflow and resets the counters and the events are lost completely.

To properly detect the overflow of rolled back events, use pmc_overflow()
even when recording events.

To reproduce:
        $ cat strcpy.c
        #include <stdio.h>
        #include <string.h>
        main()
        {
                char buf[256];

                alarm(5);
                while(1)
                        strcpy(buf, "string1");
        }

        $ perf record -e r20014 ./strcpy
        $ perf report -n > report.1
        $ perf stat -e r20014 > report.2
        # Compare report.1 and report.2
Reported-by: Maynard Johnson <mpjohn@us.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

The enhanced prefetch hint patches corrupt the condition register
that was used to check if we are in interrupt. Fix this by using cr1.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

"powerpc: Use enhanced touch instructions in POWER7
copy_to_user/copy_from_user" was applied twice. Remove one.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Directly comparing current->personality against PER_LINUX32 doesn't work
in cases when any of the personality flags stored in the top three bytes
are used.

Directly forcefully setting personality to PER_LINUX32 or PER_LINUX
discards any flags stored in the top three bytes

Use personality() macro to compare only PER_MASK bytes and make sure that
we are setting only the bits that should be set, instead of overwriting
the whole value.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Checking for device mask to cover the whole IOMMU table is too strict.
IOMMU allocators should handle mask constraint properly for each
allocation.

The patch enables to use old AirPort Extreme cards on PowerMacs with
more than 1GB of memory; without the patch the driver init fails with:

  b43-pci-bridge 0001:01:01.0: Warning: IOMMU window too big for device mask
  b43-pci-bridge 0001:01:01.0: mask: 0x3fffffff, table end: 0x80000000
  b43-phy0 ERROR: The machine/kernel does not support the required 30-bit DMA mask
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

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

For powerpc BooKE and e200, singlestep is handled on the critical/dbg
exception stack. This causes current_thread_info() to fail for kgdb
internal, so previously We work around this issue by copying
the thread_info from the kernel stack before calling kgdb_handle_exception,
and copying it back afterwards.

But actually we don't do this properly. We should backup current_thread_info
then restore that when exit.
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

We need to skip a breakpoint exception when it occurs after
a breakpoint has already been removed.
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

The kgdb_single_step flag has the possibility to indefinitely
hang the system on an SMP system.

The x86 arch have the same problem, and that problem was fixed by
commit 8097551d(kgdb,x86: do not set kgdb_single_step
on x86). This patch does the same behaviors as x86's patch.
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>