linux-kernel - [PATCH tip/sched/membarrier 4/5] membarrier: Remove unused code for architectures without membarrier hooks

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Date:   Fri, 13 Oct 2017 09:12:24 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, mathieu.desnoyers@...icios.com,
        peterz@...radead.org, boqun.feng@...il.com, ahh@...gle.com,
        maged.michael@...il.com, gromer@...gle.com, avi@...lladb.com,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        davejwatson@...com, stern@...land.harvard.edu, will.deacon@....com,
        luto@...nel.org, viro@...iv.linux.org.uk, piggin@...il.com,
        linux-arch@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH tip/sched/membarrier 4/5] membarrier: Remove unused code for architectures without membarrier hooks

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

Architectures without membarrier hooks don't need to emit the
empty membarrier_arch_switch_mm() static inline when
CONFIG_MEMBARRIER=y.

Adapt the CONFIG_MEMBARRIER=n counterpart to only emit the empty
membarrier_arch_switch_mm() for architectures with membarrier hooks.

Reported-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@...il.com>
CC: Andrew Hunter <ahh@...gle.com>
CC: Maged Michael <maged.michael@...il.com>
CC: gromer@...gle.com
CC: Avi Kivity <avi@...lladb.com>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC: Paul Mackerras <paulus@...ba.org>
CC: Michael Ellerman <mpe@...erman.id.au>
CC: Dave Watson <davejwatson@...com>
CC: Alan Stern <stern@...land.harvard.edu>
CC: Will Deacon <will.deacon@....com>
CC: Andy Lutomirski <luto@...nel.org>
CC: Ingo Molnar <mingo@...hat.com>
CC: Alexander Viro <viro@...iv.linux.org.uk>
CC: linuxppc-dev@...ts.ozlabs.org
CC: linux-arch@...r.kernel.org
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/sched/mm.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index e4955d293687..40379edac388 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -221,10 +221,6 @@ static inline void memalloc_noreclaim_restore(unsigned int flags)
 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
 #include <asm/membarrier.h>
 #else
-static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
-		struct mm_struct *next, struct task_struct *tsk)
-{
-}
 static inline void membarrier_arch_fork(struct task_struct *t,
 		unsigned long clone_flags)
 {
@@ -253,10 +249,12 @@ static inline void membarrier_execve(struct task_struct *t)
 	membarrier_arch_execve(t);
 }
 #else
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
 static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
 		struct mm_struct *next, struct task_struct *tsk)
 {
 }
+#endif
 static inline void membarrier_fork(struct task_struct *t,
 		unsigned long clone_flags)
 {
-- 
2.5.2