arch: Remove cmpxchg_double

No moar users, remove the monster.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20230531132323.991907085@infradead.org

percpu: Add {raw,this}_cpu_try_cmpxchg()

Add the try_cmpxchg() form to the per-cpu ops.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20230531132323.587480729@infradead.org

sched/core: Always inline __this_cpu_preempt_check()

Quite a few unnecessary instrumentation calls are generated via the
no-op __this_cpu_preempt_check() call, if it gets uninlined by the
compiler:

vmlinux.o: warning: objtool: in_entry_stack+0x9: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: default_do_nmi+0x10: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: fpu_idle_fpregs+0x41: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: kvm_read_and_reset_apf_flags+0x1: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: lockdep_hardirqs_on+0xb0: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: lockdep_hardirqs_off+0xae: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_nmi_enter+0x69: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_nmi_exit+0x32: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: acpi_processor_ffh_cstate_enter+0x9: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: acpi_idle_enter+0x43: call to __this_cpu_preempt_check() leaves .noinstr.text section
vmlinux.o: warning: objtool: acpi_idle_enter_s2idle+0x45: call to __this_cpu_preempt_check() leaves .noinstr.text section

Mark it __always_inline.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.089981974@infradead.org

mm: fix spelling mistakes in header files

Fix some spelling mistakes in comments:
successfull ==> successful
potentialy ==> potentially
alloced ==> allocated
indicies ==> indices
wont ==> won't
resposible ==> responsible
dirtyness ==> dirtiness
droppped ==> dropped
alread ==> already
occured ==> occurred
interupts ==> interrupts
extention ==> extension
slighly ==> slightly
Dont't ==> Don't

Link: https://lkml.kernel.org/r/20210531034849.9549-2-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

treewide: Convert macro and uses of __section(foo) to __section("foo")

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@gooogle.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

percpu: Separate decrypted varaibles anytime encryption can be enabled

CONFIG_VIRTUALIZATION may not be enabled for memory encrypted guests. If
disabled, decrypted per-CPU variables may end up sharing the same page
with variables that should be left encrypted.

Always separate per-CPU variables that should be decrypted into their own
page anytime memory encryption can be enabled in the guest rather than
rely on any other config option that may not be enabled.

Fixes: ac26963a1175 ("percpu: Introduce DEFINE_PER_CPU_DECRYPTED")
Cc: stable@vger.kernel.org # 4.15+
Signed-off-by: Erdem Aktas <erdemaktas@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>

Revert "percpu: add __percpu to SHIFT_PERCPU_PTR"

This reverts commit 825dbc6ff7a3a063ea91be7d94af940080b0c991.

I mistakenly applied this and only now have thought about it a little
more and had time to evaluate a kbuild error for dmaengine.

Once we're calling RELOC_HIDE, we're moving back into the __kernel
address space and letting users interact with the actual memory address
rather than in __percpu which is before adding the offsets.

Signed-off-by: Dennis Zhou <dennis@kernel.org>

percpu: add __percpu to SHIFT_PERCPU_PTR

The SHIFT_PERCPU_PTR() returns a pointer used by a number
of functions that expect the pointer to be __percpu annotated
(sparse address space 3). Adding __percpu to this makes the
following sparse warnings go away.

Note, this then creates the problem the __percup is marked
as noderef, which may need removing for some of the internal
functions, or to remove other warnings.

mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Dennis Zhou <dennis@kernel.org>

treewide: Add SPDX license identifier for missed files

Add SPDX license identifiers to all files which:

- Have no license information of any form

- Have EXPORT_.*_SYMBOL_GPL inside which was used in the
initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

percpu: remove PER_CPU_DEF_ATTRIBUTES macro

The macro is not used:

$ grep -r PER_CPU_DEF_ATTRIBUTES
include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \
include/asm-generic/percpu.h:#ifndef PER_CPU_DEF_ATTRIBUTES
include/asm-generic/percpu.h:#define PER_CPU_DEF_ATTRIBUTES

It was added with b01e8dc34379 ("alpha: fix percpu build breakage") and
removed in 2009 with b01e8dc34379..6088464cf1ae.

Link: http://lkml.kernel.org/r/20180821164904.qqhcduimjznods66@K55DR.localdomain
Signed-off-by: Alexander Pateenok <pateenoc@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

percpu: Introduce DEFINE_PER_CPU_DECRYPTED

KVM guest defines three per-CPU variables (steal-time, apf_reason, and
kvm_pic_eoi) which are shared between a guest and a hypervisor.

When SEV is active, memory is encrypted with a guest-specific key, and if
the guest OS wants to share the memory region with the hypervisor then it
must clear the C-bit (i.e set decrypted) before sharing it.

DEFINE_PER_CPU_DECRYPTED can be used to define the per-CPU variables
which will be shared between a guest and a hypervisor.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Borislav Petkov <bp@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: linux-arch@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: kvm@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Lameter <cl@linux.com>
Link: https://lkml.kernel.org/r/20171020143059.3291-16-brijesh.singh@amd.com

percpu: update incorrect comment for this_cpu_*() operations

this_cpu_*() ops have been protected against both preemption and
interrupts for quite a while now. We apparently forgot to update the
comment. Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>

percpu: remove __get_cpu_var and __raw_get_cpu_var macros

No user is left in the kernel source tree. Therefore we can drop the
definitions.

This is the final merge of the transition away from __get_cpu_var. After
this patch the kernel will not build if anyone uses __get_cpu_var.

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

percpu: Remove __this_cpu_ptr

The __this_cpu_ptr macro is no longer in use so drop it.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

core: fix typo in percpu read_mostly section

This fixes a typo that named the read_mostly section of percpu as
readmostly. It works fine with SMP because the linker script specifies
.data..percpu..readmostly. However, UP kernel builds don't have percpu
sections defined and the non-percpu version of the section is called
data..read_mostly, so .data..readmostly will float around and may break
things unexpectedly.

Looking at the original change that introduced data..percpu..readmostly
(commit c957ef2c59e952803766ddc22e89981ab534606f), it looks like this
was the original intention.

Tested: Built UP kernel and confirmed the sections got merged.

- Before the patch:
$ objdump -h vmlinux.o | grep '\.data\.\.read.*mostly'
38 .data..read_mostly 00004418 0000000000000000 0000000000000000 00431ac0 2**6
50 .data..readmostly 00000014 0000000000000000 0000000000000000 00444000 2**3

- After the patch:
$ objdump -h vmlinux.o | grep '\.data\.\.read.*mostly'
38 .data..read_mostly 00004438 0000000000000000 0000000000000000 00431ac0 2**6

Signed-off-by: Zhengyu He <hzy@google.com>
Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

percpu: invoke __verify_pcpu_ptr() from the generic part of accessors and operations

__verify_pcpu_ptr() is used to verify that a specified parameter is
actually an percpu pointer by percpu accessor and operation
implementations. Currently, where it's called isn't clearly defined
and we just ensure that it's invoked at least once for all accessors
and operations.

The lack of clarity on when it should be called isn't nice and given
that this is a completely generic issue, there's no reason to make
archs worry about it.

This patch updates __verify_pcpu_ptr() invocations such that it's
always invoked from the final generic wrapper once per access or
operation. As this is already the case for {raw|this}_cpu_*()
definitions through __pcpu_size_*(), only the {raw|per|this}_cpu_ptr()
accessors need to be updated.

This change makes it unnecessary for archs to worry about
__verify_pcpu_ptr(). x86's arch_raw_cpu_ptr() is updated accordingly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>

percpu: preffity percpu header files

percpu macros are difficult to read. It's partly because they're
fairly complex but also because they simply lack visual and
conventional consistency to an unusual degree. The preceding patches
tried to organize macro definitions consistently by their roles. This
patch makes the following cosmetic changes to improve overall
readability.

* Use consistent convention for multi-line macro definitions - "do {"
or "({" are now put on their own lines and the line continuing '\'
are all put on the same column.

* Temp variables used inside macro are consistently given "__" prefix.

* When a macro argument is passed to another macro or a function,
putting extra parenthses around it doesn't help anything. Don't put
them.

* _this_cpu_generic_*() are renamed to this_cpu_generic_*() so that
they're consistent with raw_cpu_generic_*().

* Reorganize raw_cpu_*() and this_cpu_*() definitions so that trivial
wrappers are collected in one place after actual operation
definitions.

* Other misc cleanups including reorganizing comments.

All changes in this patch are cosmetic and cause no functional
difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: use raw_cpu_*() to define __this_cpu_*()

__this_cpu_*() operations are the same as raw_cpu_*() operations
except for the added __this_cpu_preempt_check(). Curiously, these
were defined using __pcu_size_call_*() instead of being layered on top
of raw_cpu_*().

Let's layer them so that __this_cpu_*() are defined in terms of
raw_cpu_*(). It's simpler and less error-prone this way.

This patch doesn't introduce any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: reorder macros in percpu header files

* In include/asm-generic/percpu.h, collect {raw|_this}_cpu_generic*()
macros into one place. They were dispersed through
{raw|this}_cpu_*_N() definitions and the visiual inconsistency was
making following the code unnecessarily difficult.

* In include/linux/percpu-defs.h, move __verify_pcpu_ptr() later in
the file so that it's right above accessor definitions where it's
actually used.

This is pure reorganization.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: move {raw|this}_cpu_*() definitions to include/linux/percpu-defs.h

We're in the process of moving all percpu accessors and operations to
include/linux/percpu-defs.h so that they're available to arch headers
without having to include full include/linux/percpu.h which may cause
cyclic inclusion dependency.

This patch moves {raw|this}_cpu_*() definitions from
include/linux/percpu.h to include/linux/percpu-defs.h. The code is
moved mostly verbatim; however, raw_cpu_*() are placed above
this_cpu_*() which is more conventional as the raw operations may be
used to defined other variants.

This is pure reorganization.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: reorganize include/linux/percpu-defs.h

Reorganize for better readability.

* Accessor definitions are collected into one place and SMP and UP now
define them in the same order.

* Definitions are layered when possible - e.g. per_cpu() is now
defined in terms of this_cpu_ptr().

* Rather pointless comment dropped.

* per_cpu(), __raw_get_cpu_var() and __get_cpu_var() are defined in a
way which can be shared between SMP and UP and moved out of
CONFIG_SMP blocks.

This patch doesn't introduce any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>

percpu: move accessors from include/linux/percpu.h to percpu-defs.h

include/linux/percpu-defs.h is gonna host all accessors and operations
so that arch headers can make use of them too without worrying about
circular dependency through include/linux/percpu.h.

This patch moves the following accessors from include/linux/percpu.h
to include/linux/percpu-defs.h.

* get/put_cpu_var()
* get/put_cpu_ptr()
* per_cpu_ptr()

This is pure reorgniazation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: include/asm-generic/percpu.h should contain only arch-overridable parts

The roles of the various percpu header files has become unclear.
There are four header files involved.

include/linux/percpu-defs.h
include/linux/percpu.h
include/asm-generic/percpu.h
arch/*/include/asm/percpu.h

The original intention for include/asm-generic/percpu.h is providing
generic definitions for arch-overridable parts; however, it now hosts
various stuff which can't be overridden by archs.

Also, include/linux/percpu-defs.h was initially added to contain
section and percpu variable definition macros so that arch header
files can make use of them without worrying about introducing cyclic
inclusion dependency by including include/linux/percpu.h; however,
arch headers sometimes need to access percpu variables too and this is
one of the reasons why some accessors were implemented in
include/linux/asm-generic/percpu.h.

Let's clear up the situation by making include/asm-generic/percpu.h
contain only arch-overridable parts and moving accessors and
operations into include/linux/percpu-defs. Note that this patch only
moves things from include/asm-generic/percpu.h.
include/linux/percpu.h will be taken care of by later patches.

This patch moves the followings.

* SHIFT_PERCPU_PTR() / VERIFY_PERCPU_PTR()
* per_cpu()
* raw_cpu_ptr()
* this_cpu_ptr()
* __get_cpu_var()
* __raw_get_cpu_var()
* __this_cpu_ptr()
* PER_CPU_[SHARED_]ALIGNED_SECTION
* PER_CPU_[SHARED_]ALIGNED_SECTION
* PER_CPU_FIRST_SECTION

This patch is pure reorganization.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>

percpu: fix spurious sparse warnings from DEFINE_PER_CPU()

When CONFIG_DEBUG_FORCE_WEAK_PER_CPU or CONFIG_ARCH_NEEDS_WEAK_PER_CPU
is set, DEFINE_PER_CPU() explodes into cryptic series of definitions
to still allow using "static" for percpu variables while keeping all
per-cpu symbols unique in the kernel image which is required for weak
symbols. This ultimately converts the actual symbol to global whether
DEFINE_PER_CPU() is prefixed with static or not.

Unfortunately, the macro forgot to add explicit extern declartion of
the actual symbol ending up defining global symbol without preceding
declaration for static definitions which naturally don't have matching
DECLARE_PER_CPU(). The only ill effect is triggering of the following
warnings.

fs/inode.c:74:8: warning: symbol 'nr_inodes' was not declared. Should it be static?
fs/inode.c:75:8: warning: symbol 'nr_unused' was not declared. Should it be static?

Fix it by adding extern declaration in the DEFINE_PER_CPU() macro.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Tested-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>

percpu: Make __verify_pcu_ptr handle per cpu pointers to arrays

__verify_pcpu_ptr() will cause a compilation failure if the type of the
pointer is a pointer to a fixed array of objects. Adding zero to the
pointer converts the type of pointer to that pointing to a single
object of the array.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

percpu: Remove the multi-page alignment facility

[DECLARE|DEFINE]_PER_CPU_MULTIPAGE_ALIGNED never really worked because
the head percpu section was only page aligned. Now that the last user
is gone (32-bit IRQ stacks), remove the generic percpu facility.

Cc: Brian Gerst <brgerst@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1288158182-1753-1-git-send-email-brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

percpu: Introduce a read-mostly percpu API

Add a new readmostly percpu section and API. This can be used to
avoid dirtying data lines which are generally not written to, which is
especially important for data which may be accessed by processors
other than the one for which the percpu area belongs to.

[ hpa: moved it *after* the page-aligned section, for obvious
reasons. ]

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
LKML-Reference: <1287544022.4571.7.camel@sli10-conroe.sh.intel.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

x86, 32-bit: Align percpu area and irq stacks to THREAD_SIZE

The irq stacks, located in the percpu-area, need to be
THREAD_SIZE aligned. Add the infrastucture to align percpu
variables to larger-than-pagesize amounts within the percpu
area, and use it to specify the alignment for the irq stacks.
Also align the percpu area itself to THREAD_SIZE.

This should make irq stacks work with 8K THREAD_SIZE.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Cc: Tejun Heo <tj@kernel.org>
Cc: hch@lst.de
LKML-Reference: <1283799222.15941.1393621887@webmail.messagingengine.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Rename .data[.percpu][.XXX] to .data[..percpu][..XXX].

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

percpu: remove compile warnings caused by __verify_pcpu_ptr()

If percpu pointer is const, __verify_pcpu_ptr() triggers warnings like
the following.

drivers/net/loopback.c: In function 'loopback_get_stats':
drivers/net/loopback.c:109: warning: initialization discards qualifiers from pointer target type

Fix it by adding const to the verification target pointer used in
__verify_pcpu_ptr().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>

percpu: make accessors check for percpu pointer in sparse

The previous patch made sparse warn about percpu variables being used
directly without going through percpu accessors. This patch
implements the other half - checking whether non percpu variable is
passed into percpu accessors.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>

percpu: add __percpu for sparse.

We have to make __kernel "__attribute__((address_space(0)))" so we can
cast to it.

tj: * put_cpu_var() update.

* Annotations added to dynamic allocator interface.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tejun Heo <tj@kernel.org>

percpu: remove per_cpu__ prefix.

Now that the return from alloc_percpu is compatible with the address
of per-cpu vars, it makes sense to hand around the address of per-cpu
variables. To make this sane, we remove the per_cpu__ prefix we used
created to stop people accidentally using these vars directly.

Now we have sparse, we can use that (next patch).

tj: * Updated to convert stuff which were missed by or added after the
original patch.

* Kill per_cpu_var() macro.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>

percpu: remove some sparse warnings

Make the following changes to remove some sparse warnings.

* Make DEFINE_PER_CPU_SECTION() declare __pcpu_unique_* before
defining it.

* Annotate pcpu_extend_area_map() that it is entered with pcpu_lock
held, releases it and then reacquires it.

* Make percpu related macros use unique nested variable names.

* While at it, add pcpu prefix to __size_call[_return]() macros as
to-be-implemented sparse annotations will add percpu specific stuff
to these macros.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>

x86/i386: Put aligned stack-canary in percpu shared_aligned section

Pack aligned things together into a special section to minimize
padding holes.

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Tejun Heo <tj@kernel.org>
LKML-Reference: <4AA035C0.9070202@goop.org>
[ queued up in tip:x86/asm because it depends on this commit:
x86/i386: Make sure stack-protector segment base is cache aligned ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

x86, percpu: Fix DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED()

DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED() put percpu variables in
.page_aligned section without adding any alignment restrictions.
Currently, this doesn't cause any problem because all users of the
macros have explicit page alignment and page-sized but it's much safer
to enforce page alignment from the macros. After all, it's what they
claim to do.

Add __aligned(PAGE_SIZE) to DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED() and
drop explicit alignment from it users.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

alpha: fix percpu build breakage

alpha percpu access requires custom SHIFT_PERCPU_PTR() definition for
modules to work around addressing range limitation. This is done via
generating inline assembly using C preprocessing which forces the
assembler to generate external reference. This happens behind the
compiler's back and makes the compiler think that static percpu variables
in modules are unused.

This used to be worked around by using __unused attribute for percpu
variables which prevent the compiler from omitting the variable; however,
recent declare/definition attribute unification change broke this as
__used can't be used for declaration. Also, in the process,
PER_CPU_ATTRIBUTES definition in alpha percpu.h got broken.

This patch adds PER_CPU_DEF_ATTRIBUTES which is only used for definitions
and make alpha use it to add __used for percpu variables in modules. This
also fixes the PER_CPU_ATTRIBUTES double definition bug.

Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: maximilian attems <max@stro.at>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

percpu: use __weak only in the definition of weak percpu variables

__weak is necessary only for definition and might even not work in
declaration. Drop it from declaration.

This change was suggested by Ivan Kokshaysky.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

percpu: implement optional weak percpu definitions

Some archs (alpha and s390) need to use weak definitions for percpu
variables in modules so that the compiler generates external
references for them.

This patch implements weak percpu definitions which arch can enable by
defining ARCH_NEEDS_WEAK_PER_CPU in arch percpu header file. This
weak definition adds the following two restrictions on percpu variable
definitions.

1. percpu symbols must be unique whether static or not
2. percpu variables can't be defined inside a function

To ensure that these restrictions are observed in generic code, config
option DEBUG_FORCE_WEAK_PER_CPU enables weak percpu definitions for
all cases.

This patch is inspired by Ivan Kokshaysky's alpha percpu patch.

[ Impact: stricter rules for percpu variables, one more debug config option ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Howells <dhowells@redhat.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

PERCPU: Collect the DECLARE/DEFINE declarations together

Collect the DECLARE/DEFINE declarations together in linux/percpu-defs.h so
that they're in one place, and give them descriptive comments, particularly
the SHARED_ALIGNED variant.

It would be nice to collect these in linux/percpu.h, but that's not possible
without sorting out the severe #include recursion between the x86 arch headers
and the general headers (and possibly other arches too).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>