Commit 261fb61a authored Sep 23, 2009 by KAMEZAWA Hiroyuki Committed by Linus Torvalds Sep 24, 2009

memcg: add comments explaining memory barriers



Add comments for the reason of smp_wmb() in mem_cgroup_commit_charge().

[akpm@linux-foundation.org: coding-style fixes]
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4b3bde4c

mm/memcontrol.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -1134,6 +1134,13 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
		}

		pc->mem_cgroup = mem;
		/*
		* We access a page_cgroup asynchronously without lock_page_cgroup().
		* Especially when a page_cgroup is taken from a page, pc->mem_cgroup
		* is accessed after testing USED bit. To make pc->mem_cgroup visible
		* before USED bit, we need memory barrier here.
		* See mem_cgroup_add_lru_list(), etc.
		*/
		smp_wmb();
		switch (ctype) {
		case MEM_CGROUP_CHARGE_TYPE_CACHE:

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