[ltt-dev] [PATCH 00/11] Simplify system dependent URCU code

[Mathieu Desnoyers]

* Paolo Bonzini (pbonzini at redhat.com) wrote:
> This patch series simplifies the system dependent code in the
> userspace RCU library by removing redundant definitions and
> moving them to common code.  The common code is then less
> subject to bitrotting because it can be tested on x86 too.

Hi Paolo,

I like the patchset in general. I have a few comments though. Once
addressed, please re-send the whole patchset, as there may be
dependencies between the individual patches.

I'll reply to the individual patches with comments.

Mathieu

> 
> 
> Patches 3 and 4 take care of urcu/arch_*.  Definitions for
> rmb/wmb/mc/rmc/wmc can often be omitted, and even mb can
> for example defer to the compiler-provided __sync_synchronize.
> 
> Patch 5 removes a redundant definition that is probably
> a residual of libatomicops, and so does patch 6.
> 
> Patches 7 to 9 take care of urcu/uatomic_arch_*, by defining
> fallbacks using __sync_* builtins.  S390 can use them completely
> without basically changing the generated code, while other
> architectures still require a little help.
> 
> Patches 10 and 11 show how this helps by supporting
> compilation to unknown architectures that support GCC
> builtins (MIPS and IA64 are serviced nicely for example),
> and by supporting Alpha (obviously chosen as an example of
> read_barrier_depends) with ~20 lines of non-comment code.
> 
> Patch 12 is not meant to be committed, but was used to test
> the atomic op implementations on x86_64.  It is not counted
> in the diffstat below.
> 
> HTH,
> 
> Paolo
> 
> Paolo Bonzini (11+1):
>   use kernel style makefile output
>   use autoconf symbolic linking
>   add urcu/arch_defaults.h
>   define sync_core for x86 PIC
>   __SIZEOF_LONG__ is always defined by GCC
>   remove compat_uatomic_cmpxchg #define from non-x86
>   add uatomic_gcc.h, use it for default definitions
>   use uatomic_gcc.h
>   move whether atomic byte/short exists to uatomic_arch_*.h
>   add Alpha support
>   support compiling on unknown architectures
>   test uatomic_gcc.h
> 
>  Makefile.am                 |   14 +-
>  configure.ac                |   15 ++-
>  tests/test_uatomic.c        |   15 +-
>  urcu/arch_alpha.h           |   49 +++++
>  urcu/arch_defaults.h        |  109 ++++++++++
>  urcu/arch_ppc.h             |   50 +-----
>  urcu/arch_s390.h            |   46 +----
>  urcu/arch_sparc64.h         |   51 +-----
>  urcu/arch_x86.h             |   68 +------
>  urcu/uatomic_arch_alpha.h   |   32 +++
>  urcu/uatomic_arch_ppc.h     |  143 +-------------
>  urcu/uatomic_arch_s390.h    |  193 +------------------
>  urcu/uatomic_arch_sparc64.h |  109 +----------
>  urcu/uatomic_arch_x86.h     |   37 ++----
>  urcu/uatomic_gcc.h          |  293 +++++++++++++++++++++++++++++++++++++++++++
>  15 files changed, 538 insertions(+), 686 deletions(-)
>  create mode 100644 urcu/arch_alpha.h
>  create mode 100644 urcu/arch_defaults.h
>  create mode 100644 urcu/uatomic_arch_alpha.h
>  create mode 100644 urcu/uatomic_gcc.h
> 
> 
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-- 
Mathieu Desnoyers
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