| Message ID | 20241113183321.491113-1-dave@stgolabs.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | riscv/futex: Optimize atomic cmpxchg | expand |
On Wed, Nov 13, 2024 at 10:33:21AM -0800, Davidlohr Bueso wrote: > Remove redundant release/acquire barriers, optimizing the lr/sc sequence > to provide conditional RCsc synchronization, per the RVWMO. > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net> > --- > arch/riscv/include/asm/futex.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h > index fc8130f995c1..72be100afa23 100644 > --- a/arch/riscv/include/asm/futex.h > +++ b/arch/riscv/include/asm/futex.h > @@ -85,7 +85,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, > > __enable_user_access(); > __asm__ __volatile__ ( > - "1: lr.w.aqrl %[v],%[u] \n" > + "1: lr.w %[v],%[u] \n" > " bne %[v],%z[ov],3f \n" > "2: sc.w.aqrl %[t],%z[nv],%[u] \n" > " bnez %[t],1b \n" atomic_cmpxchg() uses yet another scheme, but this does also look good to me: FWIW, Reviewed-by: Andrea Parri <parri.andrea@gmail.com> Andrea
diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h index fc8130f995c1..72be100afa23 100644 --- a/arch/riscv/include/asm/futex.h +++ b/arch/riscv/include/asm/futex.h @@ -85,7 +85,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, __enable_user_access(); __asm__ __volatile__ ( - "1: lr.w.aqrl %[v],%[u] \n" + "1: lr.w %[v],%[u] \n" " bne %[v],%z[ov],3f \n" "2: sc.w.aqrl %[t],%z[nv],%[u] \n" " bnez %[t],1b \n"
Remove redundant release/acquire barriers, optimizing the lr/sc sequence to provide conditional RCsc synchronization, per the RVWMO. Signed-off-by: Davidlohr Bueso <dave@stgolabs.net> --- arch/riscv/include/asm/futex.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)