[PATCH V11 01/17] asm-generic: ticket-lock: Reuse arch_spinlock_t of qspinlock

[Guo Ren]

On Tue, Sep 12, 2023 at 3:05 AM Leonardo Brás <leobras at redhat.com> wrote:
>
> On Sun, 2023-09-10 at 04:28 -0400, guoren at kernel.org wrote:
> > From: Guo Ren <guoren at linux.alibaba.com>
> >
> > The arch_spinlock_t of qspinlock has contained the atomic_t val, which
> > satisfies the ticket-lock requirement. Thus, unify the arch_spinlock_t
> > into qspinlock_types.h. This is the preparation for the next combo
> > spinlock.
> >
> > Signed-off-by: Guo Ren <guoren at kernel.org>
> > Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> > ---
> >  include/asm-generic/spinlock.h       | 14 +++++++-------
> >  include/asm-generic/spinlock_types.h | 12 ++----------
> >  2 files changed, 9 insertions(+), 17 deletions(-)
> >
> > diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h
> > index 90803a826ba0..4773334ee638 100644
> > --- a/include/asm-generic/spinlock.h
> > +++ b/include/asm-generic/spinlock.h
> > @@ -32,7 +32,7 @@
> >
> >  static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
> >  {
> > -     u32 val = atomic_fetch_add(1<<16, lock);
> > +     u32 val = atomic_fetch_add(1<<16, &lock->val);
> >       u16 ticket = val >> 16;
> >
> >       if (ticket == (u16)val)
> > @@ -46,31 +46,31 @@ static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
> >        * have no outstanding writes due to the atomic_fetch_add() the extra
> >        * orderings are free.
> >        */
> > -     atomic_cond_read_acquire(lock, ticket == (u16)VAL);
> > +     atomic_cond_read_acquire(&lock->val, ticket == (u16)VAL);
> >       smp_mb();
> >  }
> >
> >  static __always_inline bool arch_spin_trylock(arch_spinlock_t *lock)
> >  {
> > -     u32 old = atomic_read(lock);
> > +     u32 old = atomic_read(&lock->val);
> >
> >       if ((old >> 16) != (old & 0xffff))
> >               return false;
> >
> > -     return atomic_try_cmpxchg(lock, &old, old + (1<<16)); /* SC, for RCsc */
> > +     return atomic_try_cmpxchg(&lock->val, &old, old + (1<<16)); /* SC, for RCsc */
> >  }
> >
> >  static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
> >  {
> >       u16 *ptr = (u16 *)lock + IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
> > -     u32 val = atomic_read(lock);
> > +     u32 val = atomic_read(&lock->val);
> >
> >       smp_store_release(ptr, (u16)val + 1);
> >  }
> >
> >  static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
> >  {
> > -     u32 val = lock.counter;
> > +     u32 val = lock.val.counter;
> >
> >       return ((val >> 16) == (val & 0xffff));
> >  }
>
> This one seems to be different in torvalds/master, but I suppose it's because of
> the requirement patches I have not merged.
>
> > @@ -84,7 +84,7 @@ static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock)
> >
> >  static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock)
> >  {
> > -     u32 val = atomic_read(lock);
> > +     u32 val = atomic_read(&lock->val);
> >
> >       return (s16)((val >> 16) - (val & 0xffff)) > 1;
> >  }
> > diff --git a/include/asm-generic/spinlock_types.h b/include/asm-generic/spinlock_types.h
> > index 8962bb730945..f534aa5de394 100644
> > --- a/include/asm-generic/spinlock_types.h
> > +++ b/include/asm-generic/spinlock_types.h
> > @@ -3,15 +3,7 @@
> >  #ifndef __ASM_GENERIC_SPINLOCK_TYPES_H
> >  #define __ASM_GENERIC_SPINLOCK_TYPES_H
> >
> > -#include <linux/types.h>
> > -typedef atomic_t arch_spinlock_t;
> > -
> > -/*
> > - * qrwlock_types depends on arch_spinlock_t, so we must typedef that before the
> > - * include.
> > - */
> > -#include <asm/qrwlock_types.h>
> > -
> > -#define __ARCH_SPIN_LOCK_UNLOCKED    ATOMIC_INIT(0)
> > +#include <asm-generic/qspinlock_types.h>
> > +#include <asm-generic/qrwlock_types.h>
> >
> >  #endif /* __ASM_GENERIC_SPINLOCK_TYPES_H */
>
> FWIW, LGTM:
>
> Reviewed-by: Leonardo Bras <leobras at redhat.com>
>
>
> Just a suggestion: In this patch I could see a lot of usage changes to
> arch_spinlock_t, and only at the end I could see the actual change in the .h
> file.
 include/asm-generic/spinlock.h       | 14 +++++++-------
 include/asm-generic/spinlock_types.h | 12 ++----------

All are .h files. So, how to use git.orderfile?

>
> In cases like this, it looks nicer to see the .h file first.
>
> I recently found out about this git diff.orderFile option, which helps to
> achieve exactly this.
>
> I use the following git.orderfile, adapted from qemu:
>
> ############################################################################
> #
> # order file for git, to produce patches which are easier to review
> # by diffing the important stuff like interface changes first.
> #
> # one-off usage:
> #   git diff -O scripts/git.orderfile ...
> #
> # add to git config:
> #   git config diff.orderFile scripts/git.orderfile
> #
>
> MAINTAINERS
>
> # Documentation
> Documentation/*
> *.rst
> *.rst.inc
>
> # build system
> Kbuild
> Makefile*
> *.mak
>
> # semantic patches
> *.cocci
>
> # headers
> *.h
> *.h.inc
>
> # code
> *.c
> *.c.inc
>
>


-- 
Best Regards
 Guo Ren