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author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2010-08-10 18:02:58 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-08-11 08:59:18 -0700 |
commit | 2bd9bb206b338888b226e70139a25a67d10007f0 (patch) | |
tree | ac556b1bfa52f06fe2998371d10edec38d5cf2a9 /mm/memcontrol.c | |
parent | 4b53433468c87794b523e4683fbd4e8e8aca1f63 (diff) | |
download | kernel_samsung_crespo-2bd9bb206b338888b226e70139a25a67d10007f0.zip kernel_samsung_crespo-2bd9bb206b338888b226e70139a25a67d10007f0.tar.gz kernel_samsung_crespo-2bd9bb206b338888b226e70139a25a67d10007f0.tar.bz2 |
memcg: clean up waiting move acct
Now, for checking a memcg is under task-account-moving, we do css_tryget()
against mc.to and mc.from. But this is just complicating things. This
patch makes the check easier.
This patch adds a spinlock to move_charge_struct and guard modification of
mc.to and mc.from. By this, we don't have to think about complicated
races arount this not-critical path.
[balbir@linux.vnet.ibm.com: don't crash on a null memcg being passed]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r-- | mm/memcontrol.c | 51 |
1 files changed, 29 insertions, 22 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 991860e..27981e7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -268,6 +268,7 @@ enum move_type { /* "mc" and its members are protected by cgroup_mutex */ static struct move_charge_struct { + spinlock_t lock; /* for from, to, moving_task */ struct mem_cgroup *from; struct mem_cgroup *to; unsigned long precharge; @@ -276,6 +277,7 @@ static struct move_charge_struct { struct task_struct *moving_task; /* a task moving charges */ wait_queue_head_t waitq; /* a waitq for other context */ } mc = { + .lock = __SPIN_LOCK_UNLOCKED(mc.lock), .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq), }; @@ -1051,26 +1053,24 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg) static bool mem_cgroup_under_move(struct mem_cgroup *mem) { - struct mem_cgroup *from = mc.from; - struct mem_cgroup *to = mc.to; + struct mem_cgroup *from; + struct mem_cgroup *to; bool ret = false; - - if (from == mem || to == mem) - return true; - - if (!from || !to || !mem->use_hierarchy) - return false; - - rcu_read_lock(); - if (css_tryget(&from->css)) { - ret = css_is_ancestor(&from->css, &mem->css); - css_put(&from->css); - } - if (!ret && css_tryget(&to->css)) { - ret = css_is_ancestor(&to->css, &mem->css); - css_put(&to->css); - } - rcu_read_unlock(); + /* + * Unlike task_move routines, we access mc.to, mc.from not under + * mutual exclusion by cgroup_mutex. Here, we take spinlock instead. + */ + spin_lock(&mc.lock); + from = mc.from; + to = mc.to; + if (!from) + goto unlock; + if (from == mem || to == mem + || (mem->use_hierarchy && css_is_ancestor(&from->css, &mem->css)) + || (mem->use_hierarchy && css_is_ancestor(&to->css, &mem->css))) + ret = true; +unlock: + spin_unlock(&mc.lock); return ret; } @@ -1406,7 +1406,7 @@ static void memcg_wakeup_oom(struct mem_cgroup *mem) static void memcg_oom_recover(struct mem_cgroup *mem) { - if (atomic_read(&mem->oom_lock)) + if (mem && atomic_read(&mem->oom_lock)) memcg_wakeup_oom(mem); } @@ -4441,11 +4441,13 @@ static int mem_cgroup_precharge_mc(struct mm_struct *mm) static void mem_cgroup_clear_mc(void) { + struct mem_cgroup *from = mc.from; + struct mem_cgroup *to = mc.to; + /* we must uncharge all the leftover precharges from mc.to */ if (mc.precharge) { __mem_cgroup_cancel_charge(mc.to, mc.precharge); mc.precharge = 0; - memcg_oom_recover(mc.to); } /* * we didn't uncharge from mc.from at mem_cgroup_move_account(), so @@ -4454,7 +4456,6 @@ static void mem_cgroup_clear_mc(void) if (mc.moved_charge) { __mem_cgroup_cancel_charge(mc.from, mc.moved_charge); mc.moved_charge = 0; - memcg_oom_recover(mc.from); } /* we must fixup refcnts and charges */ if (mc.moved_swap) { @@ -4479,9 +4480,13 @@ static void mem_cgroup_clear_mc(void) mc.moved_swap = 0; } + spin_lock(&mc.lock); mc.from = NULL; mc.to = NULL; mc.moving_task = NULL; + spin_unlock(&mc.lock); + memcg_oom_recover(from); + memcg_oom_recover(to); wake_up_all(&mc.waitq); } @@ -4510,12 +4515,14 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss, VM_BUG_ON(mc.moved_charge); VM_BUG_ON(mc.moved_swap); VM_BUG_ON(mc.moving_task); + spin_lock(&mc.lock); mc.from = from; mc.to = mem; mc.precharge = 0; mc.moved_charge = 0; mc.moved_swap = 0; mc.moving_task = current; + spin_unlock(&mc.lock); ret = mem_cgroup_precharge_mc(mm); if (ret) |