From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        David Laight <David.Laight@aculab.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Eduardo Valentin <eduval@amazon.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>, Juergen Gross <jgross@suse.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Will Deacon <will.deacon@arm.com>, aliguori@amazon.com,
        daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com,
        linux-mm@kvack.org, Ingo Molnar <mingo@kernel.org>
Subject: [PATCH 4.14 23/74] x86/mm: Remove superfluous barriers
Date: Wed, 27 Dec 2017 17:45:56 +0100
Message-Id: <20171227164615.031202968@linuxfoundation.org>
In-Reply-To: <20171227164614.109898944@linuxfoundation.org>
References: <20171227164614.109898944@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@infradead.org>

commit b5fc6d943808b570bdfbec80f40c6b3855f1c48b upstream.

atomic64_inc_return() already implies smp_mb() before and after.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/tlbflush.h |    8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -60,19 +60,13 @@ static inline void invpcid_flush_all_non
 
 static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
 {
-	u64 new_tlb_gen;
-
 	/*
 	 * Bump the generation count.  This also serves as a full barrier
 	 * that synchronizes with switch_mm(): callers are required to order
 	 * their read of mm_cpumask after their writes to the paging
 	 * structures.
 	 */
-	smp_mb__before_atomic();
-	new_tlb_gen = atomic64_inc_return(&mm->context.tlb_gen);
-	smp_mb__after_atomic();
-
-	return new_tlb_gen;
+	return atomic64_inc_return(&mm->context.tlb_gen);
 }
 
 #ifdef CONFIG_PARAVIRT