1. 07 5月, 2014 1 次提交
    • V
      sched: Rework sched_domain topology definition · 143e1e28
      Vincent Guittot 提交于
      We replace the old way to configure the scheduler topology with a new method
      which enables a platform to declare additionnal level (if needed).
      
      We still have a default topology table definition that can be used by platform
      that don't want more level than the SMT, MC, CPU and NUMA ones. This table can
      be overwritten by an arch which either wants to add new level where a load
      balance make sense like BOOK or powergating level or wants to change the flags
      configuration of some levels.
      
      For each level, we need a function pointer that returns cpumask for each cpu,
      a function pointer that returns the flags for the level and a name. Only flags
      that describe topology, can be set by an architecture. The current topology
      flags are:
      
       SD_SHARE_CPUPOWER
       SD_SHARE_PKG_RESOURCES
       SD_NUMA
       SD_ASYM_PACKING
      
      Then, each level must be a subset on the next one. The build sequence of the
      sched_domain will take care of removing useless levels like those with 1 CPU
      and those with the same CPU span and no more relevant information for
      load balancing than its children.
      Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
      Tested-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
      Reviewed-by: NPreeti U Murthy <preeti@linux.vnet.ibm.com>
      Reviewed-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Bjorn Helgaas <bhelgaas@google.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Hanjun Guo <hanjun.guo@linaro.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Jason Low <jason.low2@hp.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: linux390@de.ibm.com
      Cc: linux-ia64@vger.kernel.org
      Cc: linux-s390@vger.kernel.org
      Link: http://lkml.kernel.org/r/1397209481-28542-2-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      143e1e28
  2. 17 4月, 2014 1 次提交
    • T
      [IA64] Change default PSR.ac from '1' to '0' (Fix erratum #237) · c0b5a64d
      Tony Luck 提交于
      April 2014 Itanium processor specification update:
      
      http://www.intel.com/content/www/us/en/processors/itanium/itanium-specification-update.html
      
      describes this erratum:
      
      =========================================================================
      237. Under a complex set of conditions, store to load forwarding for a
      sub 8-byte load may complete incorrectly
      
      Problem: A load instruction may complete incorrectly when a code sequence
      using 4-byte or smaller load and store operations to the same address
      is executed in combination with specific timing of all the following
      concurrent conditions: store to load forwarding, alignment checking
      enabled, a mis-predicted branch, and complex cache utilization activity.
      
      Implication: The affected sub 8-byte instruction may complete
      incorrectly resulting in unpredictable system behavior. There is an
      extremely low probability of exposure due to the significant number of
      complex microarchitectural concurrent conditions required to encounter
      the erratum.
      
      Workaround: Set PSR.ac = 0 to completely avoid the erratum. Disabling
      Hyper-Threading will significantly reduce exposure to the conditions
      that contribute to encountering the erratum.
      
      Status: See the Summary Table of Changes for the affected steppings.
      =========================================================================
      
      [Table of changes essentially lists all models from McKinley to Tukwila]
      
      The PSR.ac bit controls whether the processor will always generate
      an unaligned reference trap (0x5a00) for a misaligned data access
      (when PSR.ac=1) or if it will let the access succeed when running
      on a cpu that implements logic to handle some unaligned accesses.
      
      Way back in 2008 in commit b704882e
        [IA64] Rationalize kernel mode alignment checking
      we made the decision to always enable strict checking. We were
      already doing so in trap/interrupt context because the common
      preamble code set this bit - but the rest of supervisor code
      (and by inheritance user code) ran with PSR.ac=0.
      
      We now reverse that decision and set PSR.ac=0 everywhere in the
      kernel (also inherited by user processes). This will avoid the
      erratum using the method described in the Itanium specification
      update.  Net effect for users is that the processor will handle
      unaligned access when it can (typically with a tiny performance
      bubble in the pipeline ... but much less invasive than taking a
      trap and having the OS perform the access).
      Signed-off-by: NTony Luck <tony.luck@intel.com>
      c0b5a64d
  3. 08 4月, 2014 1 次提交
  4. 29 3月, 2014 1 次提交
  5. 20 3月, 2014 5 次提交
    • A
      audit: Add CONFIG_HAVE_ARCH_AUDITSYSCALL · 7a017721
      AKASHI Takahiro 提交于
      Currently AUDITSYSCALL has a long list of architecture depencency:
             depends on AUDIT && (X86 || PARISC || PPC || S390 || IA64 || UML ||
      		SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT) || ALPHA)
      The purpose of this patch is to replace it with HAVE_ARCH_AUDITSYSCALL
      for simplicity.
      Signed-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
      Acked-by: Will Deacon <will.deacon@arm.com> (arm)
      Acked-by: Richard Guy Briggs <rgb@redhat.com> (audit)
      Acked-by: Matt Turner <mattst88@gmail.com> (alpha)
      Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
      Signed-off-by: NEric Paris <eparis@redhat.com>
      7a017721
    • S
      ia64, err-inject: Fix CPU hotplug callback registration · f2e48a89
      Srivatsa S. Bhat 提交于
      Subsystems that want to register CPU hotplug callbacks, as well as perform
      initialization for the CPUs that are already online, often do it as shown
      below:
      
      	get_online_cpus();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	register_cpu_notifier(&foobar_cpu_notifier);
      
      	put_online_cpus();
      
      This is wrong, since it is prone to ABBA deadlocks involving the
      cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
      with CPU hotplug operations).
      
      Instead, the correct and race-free way of performing the callback
      registration is:
      
      	cpu_notifier_register_begin();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	/* Note the use of the double underscored version of the API */
      	__register_cpu_notifier(&foobar_cpu_notifier);
      
      	cpu_notifier_register_done();
      
      Fix the error injection code in ia64 by using this latter form of callback
      registration.
      
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      f2e48a89
    • S
      ia64, topology: Fix CPU hotplug callback registration · f5a7d445
      Srivatsa S. Bhat 提交于
      Subsystems that want to register CPU hotplug callbacks, as well as perform
      initialization for the CPUs that are already online, often do it as shown
      below:
      
      	get_online_cpus();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	register_cpu_notifier(&foobar_cpu_notifier);
      
      	put_online_cpus();
      
      This is wrong, since it is prone to ABBA deadlocks involving the
      cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
      with CPU hotplug operations).
      
      Instead, the correct and race-free way of performing the callback
      registration is:
      
      	cpu_notifier_register_begin();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	/* Note the use of the double underscored version of the API */
      	__register_cpu_notifier(&foobar_cpu_notifier);
      
      	cpu_notifier_register_done();
      
      Fix the topology code in ia64 by using this latter form of callback
      registration.
      
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      f5a7d445
    • S
      ia64, palinfo: Fix CPU hotplug callback registration · 9f37bca9
      Srivatsa S. Bhat 提交于
      Subsystems that want to register CPU hotplug callbacks, as well as perform
      initialization for the CPUs that are already online, often do it as shown
      below:
      
      	get_online_cpus();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	register_cpu_notifier(&foobar_cpu_notifier);
      
      	put_online_cpus();
      
      This is wrong, since it is prone to ABBA deadlocks involving the
      cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
      with CPU hotplug operations).
      
      Instead, the correct and race-free way of performing the callback
      registration is:
      
      	cpu_notifier_register_begin();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	/* Note the use of the double underscored version of the API */
      	__register_cpu_notifier(&foobar_cpu_notifier);
      
      	cpu_notifier_register_done();
      
      Fix the palinfo code in ia64 by using this latter form of callback
      registration.
      
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      9f37bca9
    • S
      ia64, salinfo: Fix hotplug callback registration · eff722b0
      Srivatsa S. Bhat 提交于
      Subsystems that want to register CPU hotplug callbacks, as well as perform
      initialization for the CPUs that are already online, often do it as shown
      below:
      
      	get_online_cpus();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	register_cpu_notifier(&foobar_cpu_notifier);
      
      	put_online_cpus();
      
      This is wrong, since it is prone to ABBA deadlocks involving the
      cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
      with CPU hotplug operations).
      
      Instead, the correct and race-free way of performing the callback
      registration is:
      
      	cpu_notifier_register_begin();
      
      	for_each_online_cpu(cpu)
      		init_cpu(cpu);
      
      	/* Note the use of the double underscored version of the API */
      	__register_cpu_notifier(&foobar_cpu_notifier);
      
      	cpu_notifier_register_done();
      
      Fix the salinfo code in ia64 by using this latter form of callback
      registration.
      
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      eff722b0
  6. 13 3月, 2014 1 次提交
    • G
      kvm: x86: ignore ioapic polarity · 100943c5
      Gabriel L. Somlo 提交于
      Both QEMU and KVM have already accumulated a significant number of
      optimizations based on the hard-coded assumption that ioapic polarity
      will always use the ActiveHigh convention, where the logical and
      physical states of level-triggered irq lines always match (i.e.,
      active(asserted) == high == 1, inactive == low == 0). QEMU guests
      are expected to follow directions given via ACPI and configure the
      ioapic with polarity 0 (ActiveHigh). However, even when misbehaving
      guests (e.g. OS X <= 10.9) set the ioapic polarity to 1 (ActiveLow),
      QEMU will still use the ActiveHigh signaling convention when
      interfacing with KVM.
      
      This patch modifies KVM to completely ignore ioapic polarity as set by
      the guest OS, enabling misbehaving guests to work alongside those which
      comply with the ActiveHigh polarity specified by QEMU's ACPI tables.
      Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
      Signed-off-by: NGabriel L. Somlo <somlo@cmu.edu>
      [Move documentation to KVM_IRQ_LINE, add ia64. - Paolo]
      Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      100943c5
  7. 12 3月, 2014 1 次提交
  8. 11 3月, 2014 2 次提交
  9. 07 3月, 2014 2 次提交
  10. 05 3月, 2014 3 次提交
  11. 01 3月, 2014 2 次提交
  12. 19 2月, 2014 2 次提交
  13. 15 2月, 2014 1 次提交
  14. 10 2月, 2014 2 次提交
    • T
      locking/mcs: Allow architecture specific asm files to be used for contended case · ddf1d169
      Tim Chen 提交于
      This patch allows each architecture to add its specific assembly optimized
      arch_mcs_spin_lock_contended and arch_mcs_spinlock_uncontended for
      MCS lock and unlock functions.
      Signed-off-by: NTim Chen <tim.c.chen@linux.intel.com>
      Cc: Scott J Norton <scott.norton@hp.com>
      Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
      Cc: AswinChandramouleeswaran <aswin@hp.com>
      Cc: George Spelvin <linux@horizon.com>
      Cc: Rik vanRiel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: MichelLespinasse <walken@google.com>
      Cc: Peter Hurley <peter@hurleysoftware.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Alex Shi <alex.shi@linaro.org>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: "Figo.zhang" <figo1802@gmail.com>
      Cc: "Paul E.McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
      Cc: Waiman Long <waiman.long@hp.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Matthew R Wilcox <matthew.r.wilcox@intel.com>
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1390347382.3138.67.camel@schen9-DESKSigned-off-by: NIngo Molnar <mingo@kernel.org>
      ddf1d169
    • T
      locking/mcs: Order the header files in Kbuild of each architecture in alphabetical order · b119fa61
      Tim Chen 提交于
      We perform a clean up of the Kbuid files in each architecture.
      We order the files in each Kbuild in alphabetical order
      by running the below script.
      
      for i in arch/*/include/asm/Kbuild
      do
              cat $i | gawk '/^generic-y/ {
                      i = 3;
                      do {
                              for (; i <= NF; i++) {
                                      if ($i == "\\") {
                                              getline;
                                              i = 1;
                                              continue;
                                      }
                                      if ($i != "")
                                              hdr[$i] = $i;
                              }
                              break;
                      } while (1);
                      next;
              }
              // {
                      print $0;
              }
              END {
                      n = asort(hdr);
                      for (i = 1; i <= n; i++)
                              print "generic-y += " hdr[i];
              }' > ${i}.sorted;
              mv ${i}.sorted $i;
      done
      Signed-off-by: NTim Chen <tim.c.chen@linux.intel.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Matthew R Wilcox <matthew.r.wilcox@intel.com>
      Cc: AswinChandramouleeswaran <aswin@hp.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: "Paul E.McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Scott J Norton <scott.norton@hp.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: "Figo.zhang" <figo1802@gmail.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Waiman Long <waiman.long@hp.com>
      Cc: Peter Hurley <peter@hurleysoftware.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Cc: Alex Shi <alex.shi@linaro.org>
      Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: George Spelvin <linux@horizon.com>
      Cc: MichelLespinasse <walken@google.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      [ Fixed build bug. ]
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      b119fa61
  15. 04 2月, 2014 2 次提交
  16. 29 1月, 2014 1 次提交
  17. 24 1月, 2014 2 次提交
  18. 22 1月, 2014 1 次提交
    • M
      mm, show_mem: remove SHOW_MEM_FILTER_PAGE_COUNT · aec6a888
      Mel Gorman 提交于
      Commit 4b59e6c4 ("mm, show_mem: suppress page counts in
      non-blockable contexts") introduced SHOW_MEM_FILTER_PAGE_COUNT to
      suppress PFN walks on large memory machines.  Commit c78e9363 ("mm:
      do not walk all of system memory during show_mem") avoided a PFN walk in
      the generic show_mem helper which removes the requirement for
      SHOW_MEM_FILTER_PAGE_COUNT in that case.
      
      This patch removes PFN walkers from the arch-specific implementations
      that report on a per-node or per-zone granularity.  ARM and unicore32
      still do a PFN walk as they report memory usage on each bank which is a
      much finer granularity where the debugging information may still be of
      use.  As the remaining arches doing PFN walks have relatively small
      amounts of memory, this patch simply removes SHOW_MEM_FILTER_PAGE_COUNT.
      
      [akpm@linux-foundation.org: fix parisc]
      Signed-off-by: NMel Gorman <mgorman@suse.de>
      Acked-by: NDavid Rientjes <rientjes@google.com>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Russell King <linux@arm.linux.org.uk>
      Cc: James Bottomley <jejb@parisc-linux.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      aec6a888
  19. 19 1月, 2014 1 次提交
    • M
      net: introduce SO_BPF_EXTENSIONS · ea02f941
      Michal Sekletar 提交于
      For user space packet capturing libraries such as libpcap, there's
      currently only one way to check which BPF extensions are supported
      by the kernel, that is, commit aa1113d9 ("net: filter: return
      -EINVAL if BPF_S_ANC* operation is not supported"). For querying all
      extensions at once this might be rather inconvenient.
      
      Therefore, this patch introduces a new option which can be used as
      an argument for getsockopt(), and allows one to obtain information
      about which BPF extensions are supported by the current kernel.
      
      As David Miller suggests, we do not need to define any bits right
      now and status quo can just return 0 in order to state that this
      versions supports SKF_AD_PROTOCOL up to SKF_AD_PAY_OFFSET. Later
      additions to BPF extensions need to add their bits to the
      bpf_tell_extensions() function, as documented in the comment.
      Signed-off-by: NMichal Sekletar <msekleta@redhat.com>
      Cc: David Miller <davem@davemloft.net>
      Reviewed-by: NDaniel Borkmann <dborkman@redhat.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      ea02f941
  20. 12 1月, 2014 1 次提交
    • P
      arch: Introduce smp_load_acquire(), smp_store_release() · 47933ad4
      Peter Zijlstra 提交于
      A number of situations currently require the heavyweight smp_mb(),
      even though there is no need to order prior stores against later
      loads.  Many architectures have much cheaper ways to handle these
      situations, but the Linux kernel currently has no portable way
      to make use of them.
      
      This commit therefore supplies smp_load_acquire() and
      smp_store_release() to remedy this situation.  The new
      smp_load_acquire() primitive orders the specified load against
      any subsequent reads or writes, while the new smp_store_release()
      primitive orders the specifed store against any prior reads or
      writes.  These primitives allow array-based circular FIFOs to be
      implemented without an smp_mb(), and also allow a theoretical
      hole in rcu_assign_pointer() to be closed at no additional
      expense on most architectures.
      
      In addition, the RCU experience transitioning from explicit
      smp_read_barrier_depends() and smp_wmb() to rcu_dereference()
      and rcu_assign_pointer(), respectively resulted in substantial
      improvements in readability.  It therefore seems likely that
      replacing other explicit barriers with smp_load_acquire() and
      smp_store_release() will provide similar benefits.  It appears
      that roughly half of the explicit barriers in core kernel code
      might be so replaced.
      
      [Changelog by PaulMck]
      Reviewed-by: N"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Acked-by: NWill Deacon <will.deacon@arm.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: Michael Ellerman <michael@ellerman.id.au>
      Cc: Michael Neuling <mikey@neuling.org>
      Cc: Russell King <linux@arm.linux.org.uk>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Victor Kaplansky <VICTORK@il.ibm.com>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Link: http://lkml.kernel.org/r/20131213150640.908486364@infradead.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      47933ad4
  21. 08 1月, 2014 1 次提交
  22. 03 1月, 2014 1 次提交
  23. 18 12月, 2013 1 次提交
  24. 13 12月, 2013 1 次提交
  25. 11 12月, 2013 1 次提交
  26. 10 12月, 2013 1 次提交
  27. 07 12月, 2013 1 次提交
    • L
      ACPI: Clean up inclusions of ACPI header files · 8b48463f
      Lv Zheng 提交于
      Replace direct inclusions of <acpi/acpi.h>, <acpi/acpi_bus.h> and
      <acpi/acpi_drivers.h>, which are incorrect, with <linux/acpi.h>
      inclusions and remove some inclusions of those files that aren't
      necessary.
      
      First of all, <acpi/acpi.h>, <acpi/acpi_bus.h> and <acpi/acpi_drivers.h>
      should not be included directly from any files that are built for
      CONFIG_ACPI unset, because that generally leads to build warnings about
      undefined symbols in !CONFIG_ACPI builds.  For CONFIG_ACPI set,
      <linux/acpi.h> includes those files and for CONFIG_ACPI unset it
      provides stub ACPI symbols to be used in that case.
      
      Second, there are ordering dependencies between those files that always
      have to be met.  Namely, it is required that <acpi/acpi_bus.h> be included
      prior to <acpi/acpi_drivers.h> so that the acpi_pci_root declarations the
      latter depends on are always there.  And <acpi/acpi.h> which provides
      basic ACPICA type declarations should always be included prior to any other
      ACPI headers in CONFIG_ACPI builds.  That also is taken care of including
      <linux/acpi.h> as appropriate.
      Signed-off-by: NLv Zheng <lv.zheng@intel.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Matthew Garrett <mjg59@srcf.ucam.org>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Acked-by: Bjorn Helgaas <bhelgaas@google.com> (drivers/pci stuff)
      Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> (Xen stuff)
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      8b48463f