kernel.git/arch/s390/include/asm/bitops.h, branch linux-4.6.y

s390/bitops: remove 31 bit related comments

2015-10-14T12:32:15Z

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/barrier: remove unnecessary serialization in atomics and bitops

2015-10-14T12:32:07Z

The principles of operation states reads are in order, writes are in order, writes can be reordered after reads, but no reads can be reordered after writes. The atomic and bitops variantes for z196 use the interlocked-access facility instructions with a memory barrier before and after the instruction. Because of the memory ordering the first barrier is unnecessary and can be removed. Acked-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: implement cache friendly test_and_set_bit_lock

2015-10-14T12:32:06Z

The generic implementation for test_and_set_bit_lock in include/asm-generic uses the standard test_and_set_bit operation. This is done with either a 'csg' or a 'loag' instruction. For both version the cache line is fetched exclusively, even if the bit is already set. The result is an increase in cache traffic, for a contented lock this is a bad idea. Acked-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky

s390: remove 31 bit support

2015-03-25T10:49:33Z

Remove the 31 bit support in order to reduce maintenance cost and effectively remove dead code. Since a couple of years there is no distribution left that comes with a 31 bit kernel. The 31 bit kernel also has been broken since more than a year before anybody noticed. In addition I added a removal warning to the kernel shown at ipl for 5 minutes: a960062e5826 ("s390: add 31 bit warning message") which let everybody know about the plan to remove 31 bit code. We didn't get any response. Given that the last 31 bit only machine was introduced in 1999 let's remove the code. Anybody with 31 bit user space code can still use the compat mode. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops,atomic: add missing memory barriers

2014-04-01T07:23:35Z

When reworking the bitops and atomic ops I missed that those instructions that got atomic behaviour only perform a "specific-operand-serialization" instead of a full "serialization". The compare-and-swap instruction used before performs a full serialization before and after the instruction is executed, which means it has full memory barrier semantics. In order to give the new bitops and atomic ops functions also full memory barrier semantics add a "bcr 14,0" before and after each of those new instructions which performs full serialization as well. This restores memory barrier semantics for bitops and atomic ops functions which return values, like e.g. atomic_add_return(), but not for functions which do not return a value, like e.g. atomic_add(). This is consistent to other architectures and what common code requires. Cc: stable@vger.kernel.org # v3.13+ Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: fix comment

2014-02-21T07:50:20Z

Fix some numbers in the comments describing the layout of the bit maps. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: rename find_first_bit_left() to find_first_bit_inv()

2013-10-24T15:16:56Z

find_first_bit_left() and friends have nothing to do with the normal LSB0 bit numbering for big endian machines used in Linux (least significant bit has bit number 0). Instead they use MSB0 bit numbering, where the most signficant bit has bit number 0. So rename find_first_bit_left() and friends to find_first_bit_inv(), to avoid any confusion. Also provide inv versions of set_bit, clear_bit and test_bit. This also removes the confusing use of e.g. set_bit() in airq.c which uses a "be_to_le" bit number conversion, which could imply that instead set_bit_le() could be used. But that is entirely wrong since the _le bitops variant uses yet another bit numbering scheme. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: use flogr instruction to implement ffs, ffs, fls, fls and fls64

2013-10-24T15:16:55Z

Since z9 109 we have the flogr instruction which can be used to implement optimized versions of __ffs, ffs, __fls, fls and fls64. So implement and use them, instead of the generic variants. This reduces the size of the kernel image (defconfig, -march=z9-109) by 19,648 bytes. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: use generic find bit functions / reimplement _left variant

2013-10-24T15:16:55Z

Just like all other architectures we should use out-of-line find bit operations, since the inline variant bloat the size of the kernel image. And also like all other architecures we should only supply optimized variants of the __ffs, ffs, etc. primitives. Therefore this patch removes the inlined s390 find bit functions and uses the generic out-of-line variants instead. The optimization of the primitives follows with the next patch. With this patch also the functions find_first_bit_left() and find_next_bit_left() have been reimplemented, since logically, they are nothing else but a find_first_bit()/find_next_bit() implementation that use an inverted __fls() instead of __ffs(). Also the restriction that these functions only work on machines which support the "flogr" instruction is gone now. This reduces the size of the kernel image (defconfig, -march=z9-109) by 144,482 bytes. Alone the size of the function build_sched_domains() gets reduced from 7 KB to 3,5 KB. We also git rid of unused functions like find_first_bit_le()... Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: optimize set_bit() for constant values

2013-10-24T15:16:53Z

Since zEC12 we have the interlocked-access facility 2 which allows to use the instructions ni/oi/xi to update a single byte in storage with compare-and-swap semantics. So change set_bit(), clear_bit() and change_bit() to generate such code instead of a compare-and-swap loop (or using the load-and-* instruction family), if possible. This reduces the text segment by yet another 8KB (defconfig). Alternatively the long displacement variants niy/oiy/xiy could have been used, but the extended displacement field is usually not needed and therefore would only increase the size of the text segment again. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

kernel.git/arch/s390/include/asm/bitops.h, branch linux-4.6.y

s390/bitops: remove 31 bit related comments

s390/barrier: remove unnecessary serialization in atomics and bitops

s390/bitops: implement cache friendly test_and_set_bit_lock

s390: remove 31 bit support

s390/bitops,atomic: add missing memory barriers

s390/bitops: fix comment

s390/bitops: rename find_first_bit_left() to find_first_bit_inv()

s390/bitops: use flogr instruction to implement __ffs, ffs, __fls, fls and fls64

s390/bitops: use generic find bit functions / reimplement _left variant

s390/bitops: optimize set_bit() for constant values

s390/bitops: use flogr instruction to implement ffs, ffs, fls, fls and fls64