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>
This commit is contained in:
parent
4b53433468
commit
2bd9bb206b
|
@ -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)
|
||||
|
|
Loading…
Reference in New Issue