mm/memcg: protect memcg_stock with a local_lock_t

The members of the per-CPU structure memcg_stock_pcp are protected by
disabling interrupts.  This is not working on PREEMPT_RT because it
creates atomic context in which actions are performed which require
preemptible context.  One example is obj_cgroup_release().

The IRQ-disable sections can be replaced with local_lock_t which
preserves the explicit disabling of interrupts while keeps the code
preemptible on PREEMPT_RT.

drain_obj_stock() drops a reference on obj_cgroup which leads to an
invocat= ion of obj_cgroup_release() if it is the last object.  This in
turn leads to recursive locking of the local_lock_t.  To avoid this,
obj_cgroup_release() = is invoked outside of the locked section.

obj_cgroup_uncharge_pages() can be invoked with the local_lock_t
acquired a= nd without it.  This will lead later to a recursion in
refill_stock().  To avoid the locking recursion provide
obj_cgroup_uncharge_pages_locked() which uses the locked version of
refill_stock().

 - Replace disabling interrupts for memcg_stock with a local_lock_t.

 - Let drain_obj_stock() return the old struct obj_cgroup which is
   passed to obj_cgroup_put() outside of the locked section.

 - Provide obj_cgroup_uncharge_pages_locked() which uses the locked
   version of refill_stock() to avoid recursive locking in
   drain_obj_stock().

Link: https://lkml.kernel.org/r/20220209014709.GA26885@xsang-OptiPlex-9020
Link: https://lkml.kernel.org/r/20220226204144.1008339-6-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: kernel test robot <oliver.sang@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions