linux-kernel - [PATCH v16 01/13] vmstat: add quiet_vmstat

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Date:   Fri,  3 Nov 2017 13:04:40 -0400
From:   Chris Metcalf <cmetcalf@...lanox.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Christoph Lameter <cl@...ux.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Chris Metcalf <cmetcalf@...lanox.com>
Subject: [PATCH v16 01/13] vmstat: add quiet_vmstat_sync function

In commit f01f17d3705b ("mm, vmstat: make quiet_vmstat lighter")
the quiet_vmstat() function became asynchronous, in the sense that
the vmstat work was still scheduled to run on the core when the
function returned.  For task isolation, we need a synchronous
version of the function that guarantees that the vmstat worker
will not run on the core on return from the function.  Add a
quiet_vmstat_sync() function with that semantic.

Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
---
 include/linux/vmstat.h | 2 ++
 mm/vmstat.c            | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index ade7cb5f1359..e0b504594593 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -264,6 +264,7 @@ extern void __dec_zone_state(struct zone *, enum zone_stat_item);
 extern void __dec_node_state(struct pglist_data *, enum node_stat_item);
 
 void quiet_vmstat(void);
+void quiet_vmstat_sync(void);
 void cpu_vm_stats_fold(int cpu);
 void refresh_zone_stat_thresholds(void);
 
@@ -366,6 +367,7 @@ static inline void __dec_node_page_state(struct page *page,
 static inline void refresh_zone_stat_thresholds(void) { }
 static inline void cpu_vm_stats_fold(int cpu) { }
 static inline void quiet_vmstat(void) { }
+static inline void quiet_vmstat_sync(void) { }
 
 static inline void drain_zonestat(struct zone *zone,
 			struct per_cpu_pageset *pset) { }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4bb13e72ac97..8ad1b84ca9cf 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1837,6 +1837,15 @@ void quiet_vmstat(void)
 }
 
 /*
+ * Synchronously quiet vmstat so the work is guaranteed not to run on return.
+ */
+void quiet_vmstat_sync(void)
+{
+	cancel_delayed_work_sync(this_cpu_ptr(&vmstat_work));
+	refresh_cpu_vm_stats(false);
+}
+
+/*
  * Shepherd worker thread that checks the
  * differentials of processors that have their worker
  * threads for vm statistics updates disabled because of
-- 
2.1.2