From ad4ba375373937817404fd92239ef4cadbded23b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 23 Apr 2010 12:26:38 -0700 Subject: [PATCH] memcg: css_id() must be called under rcu_read_lock() This patch fixes task_in_mem_cgroup(), mem_cgroup_uncharge_swapcache(), mem_cgroup_move_swap_account(), and is_target_pte_for_mc() to protect calls to css_id(). An additional RCU lockdep splat was reported for memcg_oom_wake_function(), however, this function is not yet in mainline as of 2.6.34-rc5. Reported-by: Li Zefan Cc: Daisuke Nishimura Cc: Balbir Singh Signed-off-by: KAMEZAWA Hiroyuki Tested-by: Li Zefan Signed-off-by: Paul E. McKenney Cc: Andrew Morton --- mm/memcontrol.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f4ede99..e06490d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -811,10 +811,12 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem) * enabled in "curr" and "curr" is a child of "mem" in *cgroup* * hierarchy(even if use_hierarchy is disabled in "mem"). */ + rcu_read_lock(); if (mem->use_hierarchy) ret = css_is_ancestor(&curr->css, &mem->css); else ret = (curr == mem); + rcu_read_unlock(); css_put(&curr->css); return ret; } @@ -2312,7 +2314,9 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout) /* record memcg information */ if (do_swap_account && swapout && memcg) { + rcu_read_lock(); swap_cgroup_record(ent, css_id(&memcg->css)); + rcu_read_unlock(); mem_cgroup_get(memcg); } if (swapout && memcg) @@ -2369,8 +2373,10 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry, { unsigned short old_id, new_id; + rcu_read_lock(); old_id = css_id(&from->css); new_id = css_id(&to->css); + rcu_read_unlock(); if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) { mem_cgroup_swap_statistics(from, false); @@ -4038,11 +4044,16 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma, put_page(page); } /* throught */ - if (ent.val && do_swap_account && !ret && - css_id(&mc.from->css) == lookup_swap_cgroup(ent)) { - ret = MC_TARGET_SWAP; - if (target) - target->ent = ent; + if (ent.val && do_swap_account && !ret) { + unsigned short id; + rcu_read_lock(); + id = css_id(&mc.from->css); + rcu_read_unlock(); + if (id == lookup_swap_cgroup(ent)) { + ret = MC_TARGET_SWAP; + if (target) + target->ent = ent; + } } return ret; } -- 1.8.2.3