On Wed, Feb 13, 2019 at 05:00:16PM -0500, Waiman Long wrote:

Currently, we have two different implementation of rwsem:
 1) CONFIG_RWSEM_GENERIC_SPINLOCK (rwsem-spinlock.c)
 2) CONFIG_RWSEM_XCHGADD_ALGORITHM (rwsem-xadd.c)

As we are going to use a single generic implementation for rwsem-xadd.c
and no architecture-specific code will be needed, there is no point
in keeping two different implementations of rwsem. In most cases, the
performance of rwsem-spinlock.c will be worse. It also doesn't get all
the performance tuning and optimizations that had been implemented in
rwsem-xadd.c over the years.

For simplication, we are going to remove rwsem-spinlock.c and make all
architectures use a single implementation of rwsem - rwsem-xadd.c.

All references to RWSEM_GENERIC_SPINLOCK and RWSEM_XCHGADD_ALGORITHM
in the code are removed.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
---
 arch/alpha/Kconfig              |   7 -
 arch/arc/Kconfig                |   3 -
 arch/arm/Kconfig                |   4 -
 arch/arm64/Kconfig              |   3 -
 arch/c6x/Kconfig                |   3 -
 arch/csky/Kconfig               |   3 -
 arch/h8300/Kconfig              |   3 -
 arch/hexagon/Kconfig            |   6 -
 arch/ia64/Kconfig               |   4 -
 arch/m68k/Kconfig               |   7 -
 arch/microblaze/Kconfig         |   6 -
 arch/mips/Kconfig               |   7 -
 arch/nds32/Kconfig              |   3 -
 arch/nios2/Kconfig              |   3 -
 arch/openrisc/Kconfig           |   6 -
 arch/parisc/Kconfig             |   6 -
 arch/powerpc/Kconfig            |   7 -
 arch/riscv/Kconfig              |   3 -
 arch/s390/Kconfig               |   6 -
 arch/sh/Kconfig                 |   6 -
 arch/sparc/Kconfig              |   8 -
 arch/unicore32/Kconfig          |   6 -
 arch/x86/Kconfig                |   3 -
 arch/x86/um/Kconfig             |   6 -
 arch/xtensa/Kconfig             |   3 -
 include/linux/rwsem-spinlock.h  |  47 ------
 include/linux/rwsem.h           |   5 -
 kernel/Kconfig.locks            |   2 +-
 kernel/locking/Makefile         |   4 +-
 kernel/locking/rwsem-spinlock.c | 339 ----------------------------------------
 kernel/locking/rwsem.h          |   3 -
 31 files changed, 2 insertions(+), 520 deletions(-)
 delete mode 100644 include/linux/rwsem-spinlock.h
 delete mode 100644 kernel/locking/rwsem-spinlock.c

Another nice cleanup, and it looks like the optimistic spinning in the xadd
implementation is predicated on ARCH_SUPPORTS_ATOMIC_RMW, so we're all good
there too.

Acked-by: Will Deacon <redacted>

Will