linux-kernel - [PATCH v3 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing

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Date:   Tue, 24 Sep 2019 18:24:28 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Leonardo Bras <leonardo@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ganesh Goudar <ganeshgr@...ux.ibm.com>,
        Allison Randal <allison@...utok.net>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Keith Busch <keith.busch@...el.com>
Subject: [PATCH v3 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing

Skips slow part of serialize_against_pte_lookup if there is no running
lockless pagetable walk.

Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>
---
 arch/powerpc/mm/book3s64/pgtable.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index 0b86884a8097..e2aa6572f03f 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -95,7 +95,8 @@ static void do_nothing(void *unused)
 void serialize_against_pte_lookup(struct mm_struct *mm)
 {
 	smp_mb();
-	smp_call_function_many(mm_cpumask(mm), do_nothing, NULL, 1);
+	if (running_lockless_pgtbl_walk(mm))
+		smp_call_function_many(mm_cpumask(mm), do_nothing, NULL, 1);
 }
 
 /*
-- 
2.20.1