locking/atomic/x86: Introduce arch_sync_try_cmpxchg()

Introduce the arch_sync_try_cmpxchg() macro to improve code using
sync_try_cmpxchg() locking primitive. The new definitions use existing
__raw_try_cmpxchg() macros, but use its own "lock; " prefix.

The new macros improve assembly of the cmpxchg loop in
evtchn_fifo_unmask() from drivers/xen/events/events_fifo.c from:

57a: 85 c0 test %eax,%eax
57c: 78 52 js 5d0 <...>
57e: 89 c1 mov %eax,%ecx
580: 25 ff ff ff af and $0xafffffff,%eax
585: c7 04 24 00 00 00 00 movl $0x0,(%rsp)
58c: 81 e1 ff ff ff ef and $0xefffffff,%ecx
592: 89 4c 24 04 mov %ecx,0x4(%rsp)
596: 89 44 24 08 mov %eax,0x8(%rsp)
59a: 8b 74 24 08 mov 0x8(%rsp),%esi
59e: 8b 44 24 04 mov 0x4(%rsp),%eax
5a2: f0 0f b1 32 lock cmpxchg %esi,(%rdx)
5a6: 89 04 24 mov %eax,(%rsp)
5a9: 8b 04 24 mov (%rsp),%eax
5ac: 39 c1 cmp %eax,%ecx
5ae: 74 07 je 5b7 <...>
5b0: a9 00 00 00 40 test $0x40000000,%eax
5b5: 75 c3 jne 57a <...>
<...>

to:

578: a9 00 00 00 40 test $0x40000000,%eax
57d: 74 2b je 5aa <...>
57f: 85 c0 test %eax,%eax
581: 78 40 js 5c3 <...>
583: 89 c1 mov %eax,%ecx
585: 25 ff ff ff af and $0xafffffff,%eax
58a: 81 e1 ff ff ff ef and $0xefffffff,%ecx
590: 89 4c 24 04 mov %ecx,0x4(%rsp)
594: 89 44 24 08 mov %eax,0x8(%rsp)
598: 8b 4c 24 08 mov 0x8(%rsp),%ecx
59c: 8b 44 24 04 mov 0x4(%rsp),%eax
5a0: f0 0f b1 0a lock cmpxchg %ecx,(%rdx)
5a4: 89 44 24 04 mov %eax,0x4(%rsp)
5a8: 75 30 jne 5da <...>
<...>
5da: 8b 44 24 04 mov 0x4(%rsp),%eax
5de: eb 98 jmp 578 <...>

The new code removes move instructions from 585: 5a6: and 5a9:
and the compare from 5ac:. Additionally, the compiler assumes that
cmpxchg success is more probable and optimizes code flow accordingly.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org

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

locking/x86: Define arch_try_cmpxchg_local()

Define target specific arch_try_cmpxchg_local(). This
definition overrides the generic arch_try_cmpxchg_local()
fallback definition and enables target-specific
implementation of try_cmpxchg_local().

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230405141710.3551-5-ubizjak@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>

x86: Fix various typos in comments

Fix ~144 single-word typos in arch/x86/ code comments.

Doing this in a single commit should reduce the churn.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-kernel@vger.kernel.org

asm-generic/atomic: Add try_cmpxchg() fallbacks

Only x86 provides try_cmpxchg() outside of the atomic_t interfaces,
provide generic fallbacks to create this interface from the widely
available cmpxchg() function.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/159870621515.1229682.15506193091065001742.stgit@devnote2

x86: Fix various typos in comments

Go over arch/x86/ and fix common typos in comments,
and a typo in an actual function argument name.

No change in functionality intended.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

x86/asm: Use CC_SET()/CC_OUT() in __cmpxchg_double()

Replace open-coded use of the SETcc instruction with CC_SET()/CC_OUT()
in __cmpxchg_double().

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/CAFULd4YdvwwhXWHqqPsGk5+TLG71ozgSscTZNsqmrm+Jzg941w@mail.gmail.com

locking/atomics: Instrument xchg()

While we instrument all of the (non-relaxed) atomic_*() functions and
cmpxchg(), we missed xchg().

Let's add instrumentation for xchg(), fixing up x86 to implement
arch_xchg().

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andy.shevchenko@gmail.com
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: catalin.marinas@arm.com
Cc: glider@google.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: parri.andrea@gmail.com
Cc: peter@hurleysoftware.com
Link: http://lkml.kernel.org/r/20180716113017.3909-5-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

locking/atomic/x86: Switch atomic.h to use atomic-instrumented.h

Add arch_ prefix to all atomic operations and include
<asm-generic/atomic-instrumented.h>. This will allow
to add KASAN instrumentation to all atomic ops.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/54f0eb64260b84199e538652e079a89b5423ad41.1517246437.git.dvyukov@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

locking/atomic/x86: Use 's64 *' for 'old' argument of atomic64_try_cmpxchg()

atomic64_try_cmpxchg() declares old argument as 'long *',
this makes it impossible to use it in portable code.
If caller passes 'long *', it becomes 32-bits on 32-bit arches.
If caller passes 's64 *', it does not compile on x86_64.

Change type of old argument to 's64 *' instead.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/fa6f77f2375150d26ea796a77e8b59195fd2ab13.1497690003.git.dvyukov@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

locking/atomic: Fix atomic_try_cmpxchg() semantics

Dmitry noted that the new atomic_try_cmpxchg() primitive is broken when
the old pointer doesn't point to the local stack.

He writes:

"Consider a classical lock-free stack push:

node->next = atomic_read(&head);
do {
} while (!atomic_try_cmpxchg(&head, &node->next, node));

This code is broken with the current implementation, the problem is
with unconditional update of *__po.

In case of success it writes the same value back into *__po, but in
case of cmpxchg success we might have lose ownership of some memory
locations and potentially over what __po has pointed to. The same
holds for the re-read of *__po. "

He also points out that this makes it surprisingly different from the
similar C/C++ atomic operation.

After investigating the code-gen differences caused by this patch; and
a number of alternatives (Linus dislikes this interface lots), we
arrived at these results (size x86_64-defconfig/vmlinux):

GCC-6.3.0:

10735757 cmpxchg
10726413 try_cmpxchg
10730509 try_cmpxchg + patch
10730445 try_cmpxchg-linus

GCC-7 (20170327):

10709514 cmpxchg
10704266 try_cmpxchg
10704266 try_cmpxchg + patch
10704394 try_cmpxchg-linus

From this we see that the patch has the advantage of better code-gen
on GCC-7 and keeps the interface roughly consistent with the C
language variant.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: a9ebf306f52c ("locking/atomic: Introduce atomic_try_cmpxchg()")
Signed-off-by: Ingo Molnar <mingo@kernel.org>

locking/atomic: Introduce atomic_try_cmpxchg()

Add a new cmpxchg interface:

bool try_cmpxchg(u{8,16,32,64} *ptr, u{8,16,32,64} *val, u{8,16,32,64} new);

Where the boolean returns the result of the compare; and thus if the
exchange happened; and in case of failure, the new value of *ptr is
returned in *val.

This allows simplification/improvement of loops like:

for (;;) {
new = val $op $imm;
old = cmpxchg(ptr, val, new);
if (old == val)
break;
val = old;
}

into:

do {
} while (!try_cmpxchg(ptr, &val, val $op $imm));

while also generating better code (GCC6 and onwards).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

x86/cmpxchg, locking/atomics: Remove superfluous definitions

cmpxchg contained definitions for unused (x)add_* operations, dating back
to the original ticket spinlock implementation. Nowadays these are
unused so remove them.

Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/1474913478-17757-1-git-send-email-n.borisov.lkml@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

x86/cpufeature: Carve out X86_FEATURE_*

Move them to a separate header and have the following
dependency:

x86/cpufeatures.h <- x86/processor.h <- x86/cpufeature.h

This makes it easier to use the header in asm code and not
include the whole cpufeature.h and add guards for asm.

Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1453842730-28463-5-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch: Remove __ARCH_HAVE_CMPXCHG

We removed the only user of this define in the rtmutex code. Get rid
of it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

x86: Simplify __HAVE_ARCH_CMPXCHG tests

Both the 32-bit and 64-bit cmpxchg.h header define __HAVE_ARCH_CMPXCHG
and there's ifdeffery which checks it. But since both bitness define it,
we can just as well move it up to the main cmpxchg header and simpify a
bit of code in doing that.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20140711104338.GB17083@pd.tnic
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

x86 cmpxchg.h: fix wrong comment

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

UAPI: (Scripted) Convert #include "..." to #include <path/...> in kernel system headers

Convert #include "..." to #include <path/...> in kernel system headers.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>

x86: Use correct byte-sized register constraint in __add()

Similar to:

2ca052a x86: Use correct byte-sized register constraint in __xchg_op()

... the __add() macro also needs to use a "q" constraint in the
byte-sized case, lest we try to generate an illegal register.

Link: http://lkml.kernel.org/r/4F7A3315.501@goop.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Leigh Scott <leigh123linux@googlemail.com>
Cc: Thomas Reitmayr <treitmayr@devbase.at>
Cc: <stable@vger.kernel.org> v3.3

x86: Use correct byte-sized register constraint in __xchg_op()

x86-64 can access the low half of any register, but i386 can only do
it with a subset of registers. 'r' causes compilation failures on i386,
but 'q' expresses the constraint properly.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Link: http://lkml.kernel.org/r/4F7A3315.501@goop.org
Reported-by: Leigh Scott <leigh123linux@googlemail.com>
Tested-by: Thomas Reitmayr <treitmayr@devbase.at>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: <stable@vger.kernel.org> v3.3

x86: Properly parenthesize cmpxchg() macro arguments

Quite oddly, all of the arguments passed through from the top
level macros to the second level which didn't need parentheses
had them, while the only expression (involving a parameter)
needing them didn't.

Very recently I got bitten by the lack thereof when using
something like "array + index" for the first operand, with
"array" being an array more narrow than int.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/4F2183A9020000780006F3E6@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

x86: Fix and improve cmpxchg_double{,_local}()

Just like the per-CPU ones they had several
problems/shortcomings:

Only the first memory operand was mentioned in the asm()
operands, and the 2x64-bit version didn't have a memory clobber
while the 2x32-bit one did. The former allowed the compiler to
not recognize the need to re-load the data in case it had it
cached in some register, while the latter was overly
destructive.

The types of the local copies of the old and new values were
incorrect (the types of the pointed-to variables should be used
here, to make sure the respective old/new variable types are
compatible).

The __dummy/__junk variables were pointless, given that local
copies of the inputs already existed (and can hence be used for
discarded outputs).

The 32-bit variant of cmpxchg_double_local() referenced
cmpxchg16b_local().

At once also:

- change the return value type to what it really is: 'bool'
- unify 32- and 64-bit variants
- abstract out the common part of the 'normal' and 'local' variants

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/4F01F12A020000780006A19B@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

x86: consolidate xchg and xadd macros

They both have a basic "put new value in location, return old value"
pattern, so they can use the same macro easily.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>

x86/cmpxchg: add a locked add() helper

Mostly to remove some conditional code in spinlock.h.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>

x86, cmpxchg: Use __compiletime_error() to make usage messages a bit nicer

Use __compiletime_error() to produce a compile-time error rather than
link-time, where available.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

x86: Add xadd helper macro

Add a common xadd implementation.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

x86, cmpxchg: Unify cmpxchg into cmpxchg.h

Everything that's actually common between 32 and 64-bit is moved into
cmpxchg.h.

xchg/cmpxchg will fail with a link error if they're passed an
unsupported size (which includes 64-bit args on 32-bit systems).

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

x86, um: ... and asm-x86 move

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>