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

[Leonardo Bras <leobras@redhat.com>]

On Wed, Sep 13, 2023 at 09:55:31AM +0800, Guo Ren wrote:
> On Tue, Sep 12, 2023 at 3:05 AM Leonardo Brás <leobras@redhat.com> wrote:
> >
> > On Sun, 2023-09-10 at 04:28 -0400, guoren@kernel.org wrote:
> > > From: Guo Ren <guoren@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@kernel.org>
> > > Signed-off-by: Guo Ren <guoren@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@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?

Yeap, you are right.

For some reason I got confused about seeing functions before type definition.

But in any way, we can get the same result with:

*types.h
*.h
*.c

Meaning 'spinlock_types.h' will appear before 'spinlock.h'.

After first suggesting this, I also sent a patch providing a default
orderFile for the kernel, and I also added this to the latest version:

https://lore.kernel.org/all/20230913075550.90934-2-leobras@redhat.com/

> 
> >
> > 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
>