linux-toradex.git/arch/x86/include/asm/bitops.h, branch v3.2

asm-generic: add another generic ext2 atomic bitops

2011-07-26T23:49:46+00:00

The majority of architectures implement ext2 atomic bitops as
test_and_{set,clear}_bit() without spinlock.

This adds this type of generic implementation in ext2-atomic-setbit.h and
use it wherever possible.

Signed-off-by: Akinobu Mita 
Suggested-by: Andreas Dilger 
Suggested-by: Arnd Bergmann 
Acked-by: Arnd Bergmann 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops: remove minix bitops from asm/bitops.h

2011-03-24T02:46:22+00:00

minix bit operations are only used by minix filesystem and useless by
other modules.  Because byte order of inode and block bitmaps is different
on each architecture like below:

m68k:
	big-endian 16bit indexed bitmaps

h8300, microblaze, s390, sparc, m68knommu:
	big-endian 32 or 64bit indexed bitmaps

m32r, mips, sh, xtensa:
	big-endian 32 or 64bit indexed bitmaps for big-endian mode
	little-endian bitmaps for little-endian mode

Others:
	little-endian bitmaps

In order to move minix bit operations from asm/bitops.h to architecture
independent code in minix filesystem, this provides two config options.

CONFIG_MINIX_FS_BIG_ENDIAN_16BIT_INDEXED is only selected by m68k.
CONFIG_MINIX_FS_NATIVE_ENDIAN is selected by the architectures which use
native byte order bitmaps (h8300, microblaze, s390, sparc, m68knommu,
m32r, mips, sh, xtensa).  The architectures which always use little-endian
bitmaps do not select these options.

Finally, we can remove minix bit operations from asm/bitops.h for all
architectures.

Signed-off-by: Akinobu Mita 
Acked-by: Arnd Bergmann 
Acked-by: Greg Ungerer 
Cc: Geert Uytterhoeven 
Cc: Roman Zippel 
Cc: Andreas Schwab 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Cc: Yoshinori Sato 
Cc: Michal Simek 
Cc: "David S. Miller" 
Cc: Hirokazu Takata 
Acked-by: Ralf Baechle 
Acked-by: Paul Mundt 
Cc: Chris Zankel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops: remove ext2 non-atomic bitops from asm/bitops.h

2011-03-24T02:46:21+00:00

As the result of conversions, there are no users of ext2 non-atomic bit
operations except for ext2 filesystem itself.  Now we can put them into
architecture independent code in ext2 filesystem, and remove from
asm/bitops.h for all architectures.

Signed-off-by: Akinobu Mita 
Cc: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops: introduce little-endian bitops for most architectures

2011-03-24T02:46:15+00:00

Introduce little-endian bit operations to the big-endian architectures
which do not have native little-endian bit operations and the
little-endian architectures.  (alpha, avr32, blackfin, cris, frv, h8300,
ia64, m32r, mips, mn10300, parisc, sh, sparc, tile, x86, xtensa)

These architectures can just include generic implementation
(asm-generic/bitops/le.h).

Signed-off-by: Akinobu Mita 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Mikael Starvik 
Cc: David Howells 
Cc: Yoshinori Sato 
Cc: "Luck, Tony" 
Cc: Ralf Baechle 
Cc: Kyle McMartin 
Cc: Matthew Wilcox 
Cc: Grant Grundler 
Cc: Paul Mundt 
Cc: Kazumoto Kojima 
Cc: Hirokazu Takata 
Cc: "David S. Miller" 
Cc: Chris Zankel 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Acked-by: Hans-Christian Egtvedt 
Acked-by: "H. Peter Anvin" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops: make asm-generic/bitops/find.h more generic

2010-10-09T19:51:44+00:00

asm-generic/bitops/find.h has the extern declarations of find_next_bit()
and find_next_zero_bit() and the macro definitions of find_first_bit()
and find_first_zero_bit(). It is only usable by the architectures which
enables CONFIG_GENERIC_FIND_NEXT_BIT and disables
CONFIG_GENERIC_FIND_FIRST_BIT.

x86 and tile enable both CONFIG_GENERIC_FIND_NEXT_BIT and
CONFIG_GENERIC_FIND_FIRST_BIT. These architectures cannot include
asm-generic/bitops/find.h in their asm/bitops.h. So ifdefed extern
declarations of find_first_bit and find_first_zero_bit() are put in
linux/bitops.h.

This makes asm-generic/bitops/find.h usable by these architectures
and use it. Also this change is needed for the forthcoming duplicated
extern declarations cleanup.

Signed-off-by: Akinobu Mita 
Signed-off-by: Arnd Bergmann 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: Chris Metcalf

x86: Avoid 'constant_test_bit()' misoptimization due to cast to non-volatile

2010-09-27T05:43:07+00:00

While debugging bit_spin_lock() hang, it was tracked down to gcc-4.4
misoptimization of non-inlined constant_test_bit() due to non-volatile
addr when 'const volatile unsigned long *addr' cast to 'unsigned long *'
with subsequent unconditional jump to pause (and not to the test) leading
to hang.

Compiling with gcc-4.3 or disabling CONFIG_OPTIMIZE_INLINING yields inlined
constant_test_bit() and correct jump, thus working around the kernel bug.

Other arches than asm-x86 may implement this slightly differently;
2.6.29 mitigates the misoptimization by changing the function prototype
(commit c4295fbb6048d85f0b41c5ced5cbf63f6811c46c) but probably fixing the issue
itself is better.

Signed-off-by: Alexander Chumachenko 
Signed-off-by: Michael Shigorin 
Acked-by: Linus Torvalds 
Signed-off-by: H. Peter Anvin

x86: Add optimized popcnt variants

2010-04-06T22:52:11+00:00

Add support for the hardware version of the Hamming weight function,
popcnt, present in CPUs which advertize it under CPUID, Function
0x0000_0001_ECX[23]. On CPUs which don't support it, we fallback to the
default lib/hweight.c sw versions.

A synthetic benchmark comparing popcnt with __sw_hweight64 showed almost
a 3x speedup on a F10h machine.

Signed-off-by: Borislav Petkov 
LKML-Reference: <20100318112015.GC11152@aftab>
Signed-off-by: H. Peter Anvin

x86, generic: mark complex bitops.h inlines as __always_inline

2009-01-13T17:56:30+00:00

Impact: reduce kernel image size

Hugh Dickins noticed that older gcc versions when the kernel
is built for code size didn't inline some of the bitops.

Mark all complex x86 bitops that have more than a single
asm statement or two as always inline to avoid this problem.

Probably should be done for other architectures too.

Ingo then found a better fix that only requires
a single line change, but it unfortunately only
works on gcc 4.3.

On older gccs the original patch still makes a ~0.3% defconfig
difference with CONFIG_OPTIMIZE_INLINING=y.

With gcc 4.1 and a defconfig like build:

    6116998 1138540  883788 8139326  7c323e vmlinux-oi-with-patch
    6137043 1138540  883788 8159371  7c808b vmlinux-optimize-inlining

~20k / 0.3% difference.

Signed-off-by: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Ingo Molnar

x86: make 'constant_test_bit()' take an unsigned bit number

2009-01-09T20:49:50+00:00

Ingo noticed that using signed arithmetic seems to confuse the gcc
inliner, and make it potentially decide that it's all too complicated.

(Yeah, yeah, it's a constant. It's always positive. Still..)

Based-on: Ingo Molnar 
Signed-off-by: Linus Torvalds

x86: Implement change_bit with immediate operand as "lock xorb"

2008-11-05T17:51:02+00:00

Impact: Minor optimization.

Implement change_bit with immediate bit count as "lock xorb". This is
similar to  "lock orb" and "lock andb"  for set_bit and clear_bit
functions.

Signed-off-by: Uros Bizjak 
Signed-off-by: H. Peter Anvin