linux-kernel - Re: vmstat: make vmstat_updater deferrable again and shut down on idle

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Message-ID: <alpine.DEB.2.20.1512141230560.25288@east.gentwo.org>
Date:	Mon, 14 Dec 2015 12:32:23 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, hannes@...xchg.org,
	penguin-kernel@...ove.SAKURA.ne.jp
Subject: Re: vmstat: make vmstat_updater deferrable again and shut down on
 idle

Hmmm... We got a race condition since quiet_vmstat touches cpu_stat_off
which may not be allocated early in the bootup sequence. Causes oopses on
boot.



Subject: vmstat: quieting vmstat requires a running system

Do not do anything unless the system is actually running. Otherwise
we may crash on bootup.

Signed-off-by: Christoph Lameter <cl@...ux.com>

Index: linux/mm/vmstat.c
===================================================================
--- linux.orig/mm/vmstat.c
+++ linux/mm/vmstat.c
@@ -1270,6 +1270,9 @@ static void vmstat_update(struct work_st
  */
 void quiet_vmstat(void)
 {
+	if (system_state != SYSTEM_RUNNING)
+		return;
+
 	do {
 		if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
 			cancel_delayed_work(this_cpu_ptr(&vmstat_work));
--
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