linux-kernel - [PATCH] mm-page_alloc-use-static-global-work

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Message-Id: <20170207202755.24571-1-mhocko@kernel.org>
Date:   Tue,  7 Feb 2017 21:27:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Hillf Danton <hillf.zj@...baba-inc.com>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH]  mm-page_alloc-use-static-global-work_struct-for-draining-per-cpu-pages-fix

From: Michal Hocko <mhocko@...e.com>

there is no need to have both pcpu_drain and pcpu_drain_mutex visible
outside of drain_all_pages. This might just attract abuse.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
Hi Andrew, Mel,
I think this would be a good cleanup to be folded into
mm-page_alloc-use-static-global-work_struct-for-draining-per-cpu-pages.patch.

 mm/page_alloc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b6411816787a..6c48053bcd81 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -92,10 +92,6 @@ EXPORT_PER_CPU_SYMBOL(_numa_mem_);
 int _node_numa_mem_[MAX_NUMNODES];
 #endif
 
-/* work_structs for global per-cpu drains */
-DEFINE_MUTEX(pcpu_drain_mutex);
-DEFINE_PER_CPU(struct work_struct, pcpu_drain);
-
 #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
 volatile unsigned long latent_entropy __latent_entropy;
 EXPORT_SYMBOL(latent_entropy);
@@ -2364,6 +2360,8 @@ static void drain_local_pages_wq(struct work_struct *work)
  */
 void drain_all_pages(struct zone *zone)
 {
+	static DEFINE_PER_CPU(struct work_struct, pcpu_drain);
+	static DEFINE_MUTEX(pcpu_drain_mutex);
 	int cpu;
 
 	/*
-- 
2.11.0