[v5,00/10] arm64: avoid out-of-line ll/sc atomics
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Message ID 20190829154834.26547-1-will@kernel.org
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  • arm64: avoid out-of-line ll/sc atomics
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Will Deacon Aug. 29, 2019, 3:48 p.m. UTC
Hi all,

This is a version five of the patches previously posted by Andrew here:

  v4: http://lkml.kernel.org/r/20190828175009.15457-1-andrew.murray@arm.com

The reason I'm posting this is because I spotted an issue with the above
when queuing it for 5.4 and fixing it ended up with me spinning a few
patches on top.

The basic problem is that by implementing our atomic routines using a
static key to select between the LL/SC and LSE variant, we rely on
CONFIG_JUMP_LABEL and therefore CC_HAS_ASM_GOTO because otherwise the
static key implementation itself is implementing using atomic routines,
which leads to complete disaster.

This patch series builds on top of Andrew's patches, with the following

  * Tidying up the header files in preparation for...
  * ...making LSE depend on JUMP_LABEL
  * Support for the 'K' constraint when it looks like it works
  * Minor massaging of commit logs

This means that LSE atomics are not available for in-kernel use when
building with a version of clang without 'asm goto' support. I really
don't see a way around this, but I've been told that clang-9 should
have this support so that's at least something.


Cc: Ard.Biesheuvel@arm.com
Cc: peterz@infradead.org
Cc: andrew.murray@arm.com
Cc: mark.rutland@arm.com
Cc: catalin.marinas@arm.com
Cc: robin.murphy@arm.com
Cc: ndesaulniers@google.com
Cc: natechancellor@gmail.com


Andrew Murray (5):
  jump_label: Don't warn on __exit jump entries
  arm64: Use correct ll/sc atomic constraints
  arm64: atomics: avoid out-of-line ll/sc atomics
  arm64: avoid using hard-coded registers for LSE atomics
  arm64: atomics: Remove atomic_ll_sc compilation unit

Will Deacon (5):
  arm64: lse: Remove unused 'alt_lse' assembly macro
  arm64: asm: Kill 'asm/atomic_arch.h'
  arm64: lse: Make ARM64_LSE_ATOMICS depend on JUMP_LABEL
  arm64: atomics: Undefine internal macros after use
  arm64: atomics: Use K constraint when toolchain appears to support it

 arch/arm64/Kconfig                    |   1 +
 arch/arm64/Makefile                   |   9 +-
 arch/arm64/include/asm/atomic.h       |  93 +++++++-
 arch/arm64/include/asm/atomic_ll_sc.h | 215 +++++++++---------
 arch/arm64/include/asm/atomic_lse.h   | 395 ++++++++++++----------------------
 arch/arm64/include/asm/cmpxchg.h      |  45 +++-
 arch/arm64/include/asm/lse.h          |  49 ++---
 arch/arm64/lib/Makefile               |  19 --
 arch/arm64/lib/atomic_ll_sc.c         |   3 -
 kernel/jump_label.c                   |   4 +-
 10 files changed, 413 insertions(+), 420 deletions(-)
 delete mode 100644 arch/arm64/lib/atomic_ll_sc.c