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mm/memcg: protect memcg_stock with a local_lock_t

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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>
This commit is contained in:
Sebastian Andrzej Siewior 2022-03-22 14:40:47 -07:00 committed by Linus Torvalds
parent af9a3b69e8
commit 5675114623
1 changed files with 38 additions and 21 deletions
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59
mm/memcontrol.c
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@ -2135,6 +2135,7 @@ void unlock_page_memcg(struct page *page)
}
struct memcg_stock_pcp {
local_lock_t stock_lock;
struct mem_cgroup *cached; /* this never be root cgroup */
unsigned int nr_pages;
@ -2150,18 +2151,21 @@ struct memcg_stock_pcp {
unsigned long flags;
#define FLUSHING_CACHED_CHARGE 0
};
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = {
.stock_lock = INIT_LOCAL_LOCK(stock_lock),
};
static DEFINE_MUTEX(percpu_charge_mutex);
#ifdef CONFIG_MEMCG_KMEM
static void drain_obj_stock(struct memcg_stock_pcp *stock);
static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock);
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
struct mem_cgroup *root_memcg);
static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages);
#else
static inline void drain_obj_stock(struct memcg_stock_pcp *stock)
static inline struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock)
{
return NULL;
}
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
struct mem_cgroup *root_memcg)
@ -2193,7 +2197,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
if (nr_pages > MEMCG_CHARGE_BATCH)
return ret;
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
if (memcg == stock->cached && stock->nr_pages >= nr_pages) {
@ -2201,7 +2205,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
ret = true;
}
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
return ret;
}
@ -2230,6 +2234,7 @@ static void drain_stock(struct memcg_stock_pcp *stock)
static void drain_local_stock(struct work_struct *dummy)
{
struct memcg_stock_pcp *stock;
struct obj_cgroup *old = NULL;
unsigned long flags;
/*
@ -2237,14 +2242,16 @@ static void drain_local_stock(struct work_struct *dummy)
* drain_stock races is that we always operate on local CPU stock
* here with IRQ disabled
*/
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
drain_obj_stock(stock);
old = drain_obj_stock(stock);
drain_stock(stock);
clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
if (old)
obj_cgroup_put(old);
}
/*
@ -2271,9 +2278,9 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
unsigned long flags;
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
__refill_stock(memcg, nr_pages);
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
}
/*
@ -3100,10 +3107,11 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
enum node_stat_item idx, int nr)
{
struct memcg_stock_pcp *stock;
struct obj_cgroup *old = NULL;
unsigned long flags;
int *bytes;
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
/*
@ -3112,7 +3120,7 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
* changes.
*/
if (stock->cached_objcg != objcg) {
drain_obj_stock(stock);
old = drain_obj_stock(stock);
obj_cgroup_get(objcg);
stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
@ -3156,7 +3164,9 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
if (nr)
mod_objcg_mlstate(objcg, pgdat, idx, nr);
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
if (old)
obj_cgroup_put(old);
}
static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
@ -3165,7 +3175,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
unsigned long flags;
bool ret = false;
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) {
@ -3173,17 +3183,17 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
ret = true;
}
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
return ret;
}
static void drain_obj_stock(struct memcg_stock_pcp *stock)
static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock)
{
struct obj_cgroup *old = stock->cached_objcg;
if (!old)
return;
return NULL;
if (stock->nr_bytes) {
unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT;
@ -3233,8 +3243,12 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
stock->cached_pgdat = NULL;
}
obj_cgroup_put(old);
stock->cached_objcg = NULL;
/*
* The `old' objects needs to be released by the caller via
* obj_cgroup_put() outside of memcg_stock_pcp::stock_lock.
*/
return old;
}
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
@ -3255,14 +3269,15 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
bool allow_uncharge)
{
struct memcg_stock_pcp *stock;
struct obj_cgroup *old = NULL;
unsigned long flags;
unsigned int nr_pages = 0;
local_irq_save(flags);
local_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
if (stock->cached_objcg != objcg) { /* reset if necessary */
drain_obj_stock(stock);
old = drain_obj_stock(stock);
obj_cgroup_get(objcg);
stock->cached_objcg = objcg;
stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
@ -3276,7 +3291,9 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
stock->nr_bytes &= (PAGE_SIZE - 1);
}
local_irq_restore(flags);
local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
if (old)
obj_cgroup_put(old);
if (nr_pages)
obj_cgroup_uncharge_pages(objcg, nr_pages);