Generic Ticket Spinlocks

From: Guo Ren <[email protected]>

Palmer:
Peter sent an RFC out about a year ago
<https://lore.kernel.org/lkml/[email protected]/>,
but after a spirited discussion it looks like we lost track of things. IIRC there was broad consensus on this being the way to go, but there was a lot of discussion so I wasn't sure. Given that it's been a year, I figured it'd be best to just send this out again formatted a bit more explicitly as a patch.

This has had almost no testing (just a build test on RISC-V defconfig), but I wanted to send it out largely as-is because I didn't have a SOB from Peter on the code. I had sent around something sort of similar in spirit, but this looks completely re-written. Just to play it safe I wanted to send out almost exactly as it was posted. I'd probably rename this tspinlock and tspinlock_types, as the mis-match kind of makes my eyes go funny, but I don't really care that much. I'll also go through the other ports and see if there's any more candidates, I seem to remember there having been more than just OpenRISC but it's been a while.

I'm in no big rush for this and given the complex HW dependencies I think it's best to target it for 5.19, that'd give us a full merge window for folks to test/benchmark it on their systems to make sure it's OK. RISC-V has a forward progress guarantee so we should be safe, but these can always trip things up.

Guo:
Update V2 with Arnd's suggestion [1].

[1] https://lore.kernel.org/linux-arch/CAK8P3a0NMPVGVw7===uEOtNnu1hr1GqimMbZT+Kea1CUxRvPmw at mail.gmail.com/raw

Changes in V2:
- Follow Arnd suggestion to make the patch series more generic.
- Add csky in the series.
- Combine RISC-V's two patches into one.
- Modify openrisc's patch to suit the new generic version.

Guo Ren (1):
csky: Move to generic ticket-spinlock

Palmer Dabbelt (1):
RISC-V: Move to ticket-spinlocks & RW locks

Peter Zijlstra (3):
asm-generic: ticket-lock: New generic ticket-based spinlock
asm-generic: qspinlock: Indicate the use of mixed-size atomics
openrisc: Move to ticket-spinlock

 arch/csky/include/asm/Kbuild               |   3 +-
 arch/csky/include/asm/spinlock.h           |  89 --------------
 arch/csky/include/asm/spinlock_types.h     |  27 -----
 arch/openrisc/Kconfig                      |   1 -
 arch/openrisc/include/asm/Kbuild           |   7 +-
 arch/openrisc/include/asm/spinlock.h       |  27 -----
 arch/openrisc/include/asm/spinlock_types.h |   7 --
 arch/riscv/Kconfig                         |   1 +
 arch/riscv/include/asm/Kbuild              |   2 +
 arch/riscv/include/asm/spinlock.h          | 135 ---------------------
 arch/riscv/include/asm/spinlock_types.h    |  25 ----
 include/asm-generic/qspinlock.h            |  30 +++++
 include/asm-generic/spinlock.h             |  11 +-
 include/asm-generic/spinlock_types.h       |  15 +++
 include/asm-generic/ticket-lock-types.h    |  11 ++
 include/asm-generic/ticket-lock.h          |  86 +++++++++++++
 16 files changed, 157 insertions(+), 320 deletions(-)
 delete mode 100644 arch/csky/include/asm/spinlock.h
 delete mode 100644 arch/csky/include/asm/spinlock_types.h
 delete mode 100644 arch/openrisc/include/asm/spinlock.h
 delete mode 100644 arch/openrisc/include/asm/spinlock_types.h
 delete mode 100644 arch/riscv/include/asm/spinlock.h
 delete mode 100644 arch/riscv/include/asm/spinlock_types.h
 create mode 100644 include/asm-generic/spinlock_types.h
 create mode 100644 include/asm-generic/ticket-lock-types.h
 create mode 100644 include/asm-generic/ticket-lock.h

2.25.1