From: Davidlohr Bueso <dave@stgolabs.net>
Date: Wed, 13 Nov 2024 18:33:21 +0000 (-0800)
Subject: riscv/futex: Optimize atomic cmpxchg
X-Git-Tag: v6.14-rc1~15^2~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9d0593da9459176396c1f2246efafbc80a828c7f;p=thirdparty%2Fkernel%2Flinux.git

riscv/futex: Optimize atomic cmpxchg

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>
Reviewed-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20241113183321.491113-1-dave@stgolabs.net
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---

diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h
index fc8130f995c1e..72be100afa236 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"