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Message-ID: <4f204c80c0a5ccb1ba88661d6f3ffea2737a2b0b.camel@redhat.com>
Date:   Mon, 03 Jul 2023 23:08:29 -0300
From:   Leonardo Brás <leobras@...hat.com>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 1/1] riscv/atomic.h: Deduplicate arch_atomic.*

On Thu, 2023-05-25 at 18:06 +0800, Guo Ren wrote:
> On Thu, May 25, 2023 at 5:31 PM Leonardo Bras Soares Passos
> <leobras@...hat.com> wrote:
> > 
> > Friendly ping?
> > 
> > On Wed, Apr 19, 2023 at 3:25 AM Leonardo Bras <leobras@...hat.com> wrote:
> > > 
> > > Some functions use mostly the same asm for 32-bit and 64-bit versions.
> > > 
> > > Make a macro that is generic enough and avoid code duplication.
> > > 
> > > Signed-off-by: Leonardo Bras <leobras@...hat.com>
> > > ---
> > >  arch/riscv/include/asm/atomic.h | 164 +++++++++++++++-----------------
> > >  1 file changed, 76 insertions(+), 88 deletions(-)
> > > 
> > > diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h
> > > index 0dfe9d857a762..85eb2edbc8219 100644
> > > --- a/arch/riscv/include/asm/atomic.h
> > > +++ b/arch/riscv/include/asm/atomic.h
> > > @@ -196,22 +196,28 @@ ATOMIC_OPS(xor, xor, i)
> > >  #undef ATOMIC_FETCH_OP
> > >  #undef ATOMIC_OP_RETURN
> > > 
> > > +#define _arch_atomic_fetch_add_unless(_prev, _rc, counter, _a, _u, sfx)        \
> > > +({                                                                     \
> > > +       __asm__ __volatile__ (                                          \
> > > +               "0:     lr." sfx "     %[p],  %[c]\n"                   \
> > > +               "       beq            %[p],  %[u], 1f\n"               \
> > > +               "       add            %[rc], %[p], %[a]\n"             \
> > > +               "       sc." sfx ".rl  %[rc], %[rc], %[c]\n"            \
> > > +               "       bnez           %[rc], 0b\n"                     \
> > > +               "       fence          rw, rw\n"                        \
> > > +               "1:\n"                                                  \
> > > +               : [p]"=&r" (_prev), [rc]"=&r" (_rc), [c]"+A" (counter)  \
> > > +               : [a]"r" (_a), [u]"r" (_u)                              \
> > > +               : "memory");                                            \
> > > +})
> > > +
> > >  /* This is required to provide a full barrier on success. */
> > >  static __always_inline int arch_atomic_fetch_add_unless(atomic_t *v, int a, int u)
> > >  {
> > >         int prev, rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.w     %[p],  %[c]\n"
> > > -               "       beq      %[p],  %[u], 1f\n"
> > > -               "       add      %[rc], %[p], %[a]\n"
> > > -               "       sc.w.rl  %[rc], %[rc], %[c]\n"
> > > -               "       bnez     %[rc], 0b\n"
> > > -               "       fence    rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               : [a]"r" (a), [u]"r" (u)
> > > -               : "memory");
> > > +       _arch_atomic_fetch_add_unless(prev, rc, v->counter, a, u, "w");
> > > +
> > >         return prev;
> > >  }
> > >  #define arch_atomic_fetch_add_unless arch_atomic_fetch_add_unless
> > > @@ -222,17 +228,8 @@ static __always_inline s64 arch_atomic64_fetch_add_unless(atomic64_t *v, s64 a,
> > >         s64 prev;
> > >         long rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.d     %[p],  %[c]\n"
> > > -               "       beq      %[p],  %[u], 1f\n"
> > > -               "       add      %[rc], %[p], %[a]\n"
> > > -               "       sc.d.rl  %[rc], %[rc], %[c]\n"
> > > -               "       bnez     %[rc], 0b\n"
> > > -               "       fence    rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               : [a]"r" (a), [u]"r" (u)
> > > -               : "memory");
> > > +       _arch_atomic_fetch_add_unless(prev, rc, v->counter, a, u, "d");
> > > +
> > >         return prev;
> > >  }
> > >  #define arch_atomic64_fetch_add_unless arch_atomic64_fetch_add_unless
> > > @@ -310,61 +307,79 @@ ATOMIC_OPS()
> > >  #undef ATOMIC_OPS
> > >  #undef ATOMIC_OP
> > > 
> > > +#define _arch_atomic_inc_unless_negative(_prev, _rc, counter, sfx)     \
> > > +({                                                                     \
> > > +       __asm__ __volatile__ (                                          \
> > > +               "0:     lr." sfx "      %[p],  %[c]\n"                  \
> > > +               "       bltz            %[p],  1f\n"                    \
> > > +               "       addi            %[rc], %[p], 1\n"               \
> > > +               "       sc." sfx ".rl   %[rc], %[rc], %[c]\n"           \
> > > +               "       bnez            %[rc], 0b\n"                    \
> > > +               "       fence           rw, rw\n"                       \
> > > +               "1:\n"                                                  \
> > > +               : [p]"=&r" (_prev), [rc]"=&r" (_rc), [c]"+A" (counter)  \
> > > +               :                                                       \
> > > +               : "memory");                                            \
> > > +})
> > > +
> > >  static __always_inline bool arch_atomic_inc_unless_negative(atomic_t *v)
> > >  {
> > >         int prev, rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.w      %[p],  %[c]\n"
> > > -               "       bltz      %[p],  1f\n"
> > > -               "       addi      %[rc], %[p], 1\n"
> > > -               "       sc.w.rl   %[rc], %[rc], %[c]\n"
> > > -               "       bnez      %[rc], 0b\n"
> > > -               "       fence     rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_inc_unless_negative(prev, rc, v->counter, "w");
> > > +
> > >         return !(prev < 0);
> > >  }
> > > 
> > >  #define arch_atomic_inc_unless_negative arch_atomic_inc_unless_negative
> > > 
> > > +#define _arch_atomic_dec_unless_positive(_prev, _rc, counter, sfx)     \
> > > +({                                                                     \
> > > +       __asm__ __volatile__ (                                          \
> > > +               "0:     lr." sfx "      %[p],  %[c]\n"                  \
> > > +               "       bgtz            %[p],  1f\n"                    \
> > > +               "       addi            %[rc], %[p], -1\n"              \
> > > +               "       sc." sfx ".rl   %[rc], %[rc], %[c]\n"           \
> > > +               "       bnez            %[rc], 0b\n"                    \
> > > +               "       fence           rw, rw\n"                       \
> > > +               "1:\n"                                                  \
> > > +               : [p]"=&r" (_prev), [rc]"=&r" (_rc), [c]"+A" (counter)  \
> > > +               :                                                       \
> > > +               : "memory");                                            \
> > > +})
> > > +
> > >  static __always_inline bool arch_atomic_dec_unless_positive(atomic_t *v)
> > >  {
> > >         int prev, rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.w      %[p],  %[c]\n"
> > > -               "       bgtz      %[p],  1f\n"
> > > -               "       addi      %[rc], %[p], -1\n"
> > > -               "       sc.w.rl   %[rc], %[rc], %[c]\n"
> > > -               "       bnez      %[rc], 0b\n"
> > > -               "       fence     rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_dec_unless_positive(prev, rc, v->counter, "w");
> > > +
> > >         return !(prev > 0);
> > >  }
> > > 
> > >  #define arch_atomic_dec_unless_positive arch_atomic_dec_unless_positive
> > > 
> > > +#define _arch_atomic_dec_if_positive(_prev, _rc, counter, sfx)         \
> > > +({                                                                     \
> > > +       __asm__ __volatile__ (                                          \
> > > +               "0:     lr." sfx "     %[p],  %[c]\n"                   \
> > > +               "       addi           %[rc], %[p], -1\n"               \
> > > +               "       bltz           %[rc], 1f\n"                     \
> > > +               "       sc." sfx ".rl  %[rc], %[rc], %[c]\n"            \
> > > +               "       bnez           %[rc], 0b\n"                     \
> > > +               "       fence          rw, rw\n"                        \
> > > +               "1:\n"                                                  \
> > > +               : [p]"=&r" (_prev), [rc]"=&r" (_rc), [c]"+A" (counter)  \
> > > +               :                                                       \
> > > +               : "memory");                                            \
> > > +})
> > > +
> > >  static __always_inline int arch_atomic_dec_if_positive(atomic_t *v)
> > >  {
> > >         int prev, rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.w     %[p],  %[c]\n"
> > > -               "       addi     %[rc], %[p], -1\n"
> > > -               "       bltz     %[rc], 1f\n"
> > > -               "       sc.w.rl  %[rc], %[rc], %[c]\n"
> > > -               "       bnez     %[rc], 0b\n"
> > > -               "       fence    rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_dec_if_positive(prev, rc, v->counter, "w");
> > > +
> > >         return prev - 1;
> > >  }
> > > 
> > > @@ -376,17 +391,8 @@ static __always_inline bool arch_atomic64_inc_unless_negative(atomic64_t *v)
> > >         s64 prev;
> > >         long rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.d      %[p],  %[c]\n"
> > > -               "       bltz      %[p],  1f\n"
> > > -               "       addi      %[rc], %[p], 1\n"
> > > -               "       sc.d.rl   %[rc], %[rc], %[c]\n"
> > > -               "       bnez      %[rc], 0b\n"
> > > -               "       fence     rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_inc_unless_negative(prev, rc, v->counter, "d");
> > > +
> > >         return !(prev < 0);
> > >  }
> > > 
> > > @@ -397,17 +403,8 @@ static __always_inline bool arch_atomic64_dec_unless_positive(atomic64_t *v)
> > >         s64 prev;
> > >         long rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.d      %[p],  %[c]\n"
> > > -               "       bgtz      %[p],  1f\n"
> > > -               "       addi      %[rc], %[p], -1\n"
> > > -               "       sc.d.rl   %[rc], %[rc], %[c]\n"
> > > -               "       bnez      %[rc], 0b\n"
> > > -               "       fence     rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_dec_unless_positive(prev, rc, v->counter, "d");
> > > +
> > >         return !(prev > 0);
> > >  }
> > > 
> > > @@ -418,17 +415,8 @@ static __always_inline s64 arch_atomic64_dec_if_positive(atomic64_t *v)
> > >         s64 prev;
> > >         long rc;
> > > 
> > > -       __asm__ __volatile__ (
> > > -               "0:     lr.d     %[p],  %[c]\n"
> > > -               "       addi      %[rc], %[p], -1\n"
> > > -               "       bltz     %[rc], 1f\n"
> > > -               "       sc.d.rl  %[rc], %[rc], %[c]\n"
> > > -               "       bnez     %[rc], 0b\n"
> > > -               "       fence    rw, rw\n"
> > > -               "1:\n"
> > > -               : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > > -               :
> > > -               : "memory");
> > > +       _arch_atomic_dec_if_positive(prev, rc, v->counter, "d");
> > > +
> > >         return prev - 1;
> > >  }
> > > 
> > > --
> > > 2.40.0
> > > 
> > 
> A safe cleanup, no problem found.
> 
> Reviewed-by: Guo Ren <guoren@...nel.org>
> 
> 

Hello Palmer,

Any chance this can get in 6.5?

Also, same question for this series:
https://patchwork.kernel.org/project/linux-riscv/list/?series=737491

Thanks!
Leo


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