BMC/Intel-BMC/linux.git/arch/s390/include/asm/bitops.h, branch dev

s390: remove 31 bit support

2015-03-25T10:49:33+00:00

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

2014-04-01T07:23:35+00:00

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

2014-02-21T07:50:20+00:00

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()

2013-10-24T15:16:56+00:00

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

2013-10-24T15:16:55+00:00

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

2013-10-24T15:16:55+00:00

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

2013-10-24T15:16:53+00:00

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

s390/bitops: remove CONFIG_SMP / simplify non-atomic bitops

2013-10-24T15:16:52+00:00

Remove CONFIG_SMP from bitops code. This reduces the C code significantly but also generates better code for the SMP case. This means that for !CONFIG_SMP set_bit() and friends now also have compare and swap semantics (read: more code). However nobody really cares for !CONFIG_SMP and this is the trade-off to simplify the SMP code which we do care about. The non-atomic bitops like __set_bit() now generate also better code because the old code did not have a __builtin_contant_p() check for the CONFIG_SMP case and therefore always generated the inline assembly variant. However the inline assemblies for the non-atomic case now got completely removed since gcc can produce better code, which accesses less memory operands. test_bit() got also a bit simplified since it did have a __builtin_constant_p() check, however two identical code pathes for each case (written differently). In result this mainly reduces the to be maintained code but is not very relevant for code generation, since there are not many non-atomic bitops usages that we care about. (code reduction defconfig kernel image before/after: 560 bytes). Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: make use of interlocked-access facility 1 instructions

2013-10-24T15:16:44+00:00

Make use of the interlocked-access facility 1 that got added with the z196 architecure. This facilility added new instructions which can atomically update a storage location without a compare-and-swap loop. E.g. setting a bit within a "long" can be done with a single instruction. The size of the kernel image gets ~30kb smaller. Considering that there are appr. 1900 bitops call sites this means that each one saves about 15-16 bytes per call site which is expected. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/bitops: fix inline assembly constraints

2013-08-22T10:20:10+00:00

Fix inline assembly contraints for non atomic bitops functions. This is broken since 2.6.34 987bcdac "[S390] use inline assembly contraints available with gcc 3.3.3". Reported-by: Andreas Krebbel Reported-by: Peter Oberparleiter Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky