linux-kernel - [PATCH 2/8] powerpc/pseries: use smp_rmb() in H

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Date:   Thu,  2 Jul 2020 17:48:33 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Nicholas Piggin <npiggin@...il.com>, Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Anton Blanchard <anton@...abs.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm-ppc@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [PATCH 2/8] powerpc/pseries: use smp_rmb() in H_CONFER spin yield

There is no need for rmb(), this allows faster lwsync here.

Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
 arch/powerpc/lib/locks.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index 6440d5943c00..47a530de733e 100644
--- a/arch/powerpc/lib/locks.c
+++ b/arch/powerpc/lib/locks.c
@@ -30,7 +30,7 @@ void splpar_spin_yield(arch_spinlock_t *lock)
 	yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
 	if ((yield_count & 1) == 0)
 		return;		/* virtual cpu is currently running */
-	rmb();
+	smp_rmb();
 	if (lock->slock != lock_value)
 		return;		/* something has changed */
 	plpar_hcall_norets(H_CONFER,
@@ -56,7 +56,7 @@ void splpar_rw_yield(arch_rwlock_t *rw)
 	yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
 	if ((yield_count & 1) == 0)
 		return;		/* virtual cpu is currently running */
-	rmb();
+	smp_rmb();
 	if (rw->lock != lock_value)
 		return;		/* something has changed */
 	plpar_hcall_norets(H_CONFER,
-- 
2.23.0