The flags member of struct memcg_stock_pcp has only one used bit:
FLUSHING_CACHED_CHARGE
Both struct member and flag were created to avoid scheduling multiple
instances of kworkers running drain_local_stock() for a single cpu.
How could this scenario happen before:
- drain_all_stock() gets called, get ownership of percpu_charge_mutex,
schedules a drain_local_stock() on cpu X, and drops ownership of
percpu_charge_mutex.
- Another thread calls drain_all_stock(), get ownership of
percpu_charge_mutex, schedules a drain_local_stock() on cpu X, ...
Since the stock draining is now performed by the thread running
drain_all_stock(), and happens before letting go of the
percpu_charge_mutex, there is no chance of another drain happening
between test_and_set_bit() and clear_bit(), so flags is now useless.
Remove the flags member of memcg_stock_pcp, its usages and the
FLUSHING_CACHED_CHARGE define.
Signed-off-by: Leonardo Bras <leobras@xxxxxxxxxx>
---
mm/memcontrol.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5b7f7c2e0232f..60712f69595e4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2183,9 +2183,6 @@ struct memcg_stock_pcp {
int nr_slab_reclaimable_b;
int nr_slab_unreclaimable_b;
#endif
-
- unsigned long flags;
-#define FLUSHING_CACHED_CHARGE 0
};
static DEFINE_PER_CPU_SHARED_ALIGNED(struct memcg_stock_pcp, memcg_stock) = {
@@ -2281,7 +2278,6 @@ static void drain_stock_from(struct memcg_stock_pcp *stock)
old = drain_obj_stock(stock);
drain_stock(stock);
- clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
spin_unlock_irqrestore(&stock->stock_lock, flags);
if (old)
@@ -2351,8 +2347,7 @@ static void drain_all_stock(struct mem_cgroup *root_memcg)
flush = true;
rcu_read_unlock();
- if (flush &&
- !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
+ if (flush)
drain_stock_from(stock);
}
migrate_enable();
--
2.39.1
