[patch 1/3] mm: memcontrol: rewrite uncharge API fix - uncharge from IRQ context

From: Johannes Weiner
Date: Mon Jul 07 2014 - 14:52:30 EST

Hugh reports:

======================================================
[ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]
3.16.0-rc2-mm1 #3 Not tainted
------------------------------------------------------
cc1/2771 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
(&(&rtpz->lock)->rlock){+.+.-.}, at: [<ffffffff811518b5>] memcg_check_events+0x17e/0x206
dd
and this task is already holding:
(&(&zone->lru_lock)->rlock){..-.-.}, at: [<ffffffff8110da3f>] release_pages+0xe7/0x239
which would create a new lock dependency:
(&(&zone->lru_lock)->rlock){..-.-.} -> (&(&rtpz->lock)->rlock){+.+.-.}

but this new dependency connects a SOFTIRQ-irq-safe lock:
(&(&zone->lru_lock)->rlock){..-.-.}
... which became SOFTIRQ-irq-safe at:
[<ffffffff810c201e>] __lock_acquire+0x59f/0x17e8
[<ffffffff810c38a6>] lock_acquire+0x61/0x78
[<ffffffff815bdfbd>] _raw_spin_lock_irqsave+0x3f/0x51
[<ffffffff8110dc0e>] pagevec_lru_move_fn+0x7d/0xf6
[<ffffffff8110dca4>] pagevec_move_tail+0x1d/0x2c
[<ffffffff8110e298>] rotate_reclaimable_page+0xb2/0xd4
[<ffffffff811018bf>] end_page_writeback+0x1c/0x45
[<ffffffff81134400>] end_swap_bio_write+0x5c/0x69
[<ffffffff8123473e>] bio_endio+0x50/0x6e
[<ffffffff81238dee>] blk_update_request+0x163/0x255
[<ffffffff81238ef7>] blk_update_bidi_request+0x17/0x65
[<ffffffff81239242>] blk_end_bidi_request+0x1a/0x56
[<ffffffff81239289>] blk_end_request+0xb/0xd
[<ffffffff813a075a>] scsi_io_completion+0x16d/0x553
[<ffffffff81399c0f>] scsi_finish_command+0xb6/0xbf
[<ffffffff813a0564>] scsi_softirq_done+0xe9/0xf0
[<ffffffff8123e8e5>] blk_done_softirq+0x79/0x8b
[<ffffffff81088675>] __do_softirq+0xfc/0x21f
[<ffffffff8108898f>] irq_exit+0x3d/0x92
[<ffffffff81032379>] do_IRQ+0xcc/0xe5
[<ffffffff815bf5ac>] ret_from_intr+0x0/0x13
[<ffffffff81443ac0>] cpuidle_enter+0x12/0x14
[<ffffffff810bb4e4>] cpu_startup_entry+0x187/0x243
[<ffffffff815a90ab>] rest_init+0x12f/0x133
[<ffffffff81970e7c>] start_kernel+0x396/0x3a3
[<ffffffff81970489>] x86_64_start_reservations+0x2a/0x2c
[<ffffffff81970552>] x86_64_start_kernel+0xc7/0xca

to a SOFTIRQ-irq-unsafe lock:
(&(&rtpz->lock)->rlock){+.+.-.}
... which became SOFTIRQ-irq-unsafe at:
... [<ffffffff810c2095>] __lock_acquire+0x616/0x17e8
[<ffffffff810c38a6>] lock_acquire+0x61/0x78
[<ffffffff815bde9f>] _raw_spin_lock+0x34/0x41
[<ffffffff811518b5>] memcg_check_events+0x17e/0x206
[<ffffffff811535bb>] commit_charge+0x260/0x26f
[<ffffffff81157004>] mem_cgroup_commit_charge+0xb1/0xdb
[<ffffffff81115b51>] shmem_getpage_gfp+0x400/0x6c2
[<ffffffff81115ecc>] shmem_write_begin+0x33/0x35
[<ffffffff81102a24>] generic_perform_write+0xb7/0x1a4
[<ffffffff8110391e>] __generic_file_write_iter+0x25b/0x29b
[<ffffffff81103999>] generic_file_write_iter+0x3b/0xa5
[<ffffffff8115a115>] new_sync_write+0x7b/0x9f
[<ffffffff8115a56c>] vfs_write+0xb5/0x169
[<ffffffff8115ae1f>] SyS_write+0x45/0x8c
[<ffffffff815bead2>] system_call_fastpath+0x16/0x1b

The soft limit tree lock needs to be IRQ-safe as it's acquired while
holding the IRQ-safe zone->lru_lock.

But more importantly, with uncharge happening in release_pages() now,
this path is executed from interrupt context.

Make the soft limit tree lock, uncharge batching, and charge
statistics IRQ-safe.

Reported-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/memcontrol.c | 108 +++++++++++++++++++++++++++++---------------------------
1 file changed, 55 insertions(+), 53 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6c3ffb02651e..1e3b27f8dc2f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -754,9 +754,11 @@ static void __mem_cgroup_remove_exceeded(struct mem_cgroup_per_zone *mz,
static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_zone *mz,
struct mem_cgroup_tree_per_zone *mctz)
{
- spin_lock(&mctz->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mctz->lock, flags);
__mem_cgroup_remove_exceeded(mz, mctz);
- spin_unlock(&mctz->lock);
+ spin_unlock_irqrestore(&mctz->lock, flags);
}


@@ -779,7 +781,9 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
* mem is over its softlimit.
*/
if (excess || mz->on_tree) {
- spin_lock(&mctz->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mctz->lock, flags);
/* if on-tree, remove it */
if (mz->on_tree)
__mem_cgroup_remove_exceeded(mz, mctz);
@@ -788,7 +792,7 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
* If excess is 0, no tree ops.
*/
__mem_cgroup_insert_exceeded(mz, mctz, excess);
- spin_unlock(&mctz->lock);
+ spin_unlock_irqrestore(&mctz->lock, flags);
}
}
}
@@ -839,9 +843,9 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
{
struct mem_cgroup_per_zone *mz;

- spin_lock(&mctz->lock);
+ spin_lock_irq(&mctz->lock);
mz = __mem_cgroup_largest_soft_limit_node(mctz);
- spin_unlock(&mctz->lock);
+ spin_unlock_irq(&mctz->lock);
return mz;
}

@@ -904,8 +908,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
struct page *page,
int nr_pages)
{
- preempt_disable();
-
/*
* Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
* counted as CACHE even if it's on ANON LRU.
@@ -930,7 +932,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
}

__this_cpu_add(memcg->stat->nr_page_events, nr_pages);
- preempt_enable();
}

unsigned long mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
@@ -1009,7 +1010,6 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
*/
static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
{
- preempt_disable();
/* threshold event is triggered in finer grain than soft limit */
if (unlikely(mem_cgroup_event_ratelimit(memcg,
MEM_CGROUP_TARGET_THRESH))) {
@@ -1022,8 +1022,6 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
do_numainfo = mem_cgroup_event_ratelimit(memcg,
MEM_CGROUP_TARGET_NUMAINFO);
#endif
- preempt_enable();
-
mem_cgroup_threshold(memcg);
if (unlikely(do_softlimit))
mem_cgroup_update_tree(memcg, page);
@@ -1031,8 +1029,7 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
if (unlikely(do_numainfo))
atomic_inc(&memcg->numainfo_events);
#endif
- } else
- preempt_enable();
+ }
}

struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
@@ -2704,8 +2701,8 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
{
struct page_cgroup *pc = lookup_page_cgroup(page);
struct zone *uninitialized_var(zone);
- struct lruvec *lruvec;
bool was_on_lru = false;
+ struct lruvec *lruvec;

VM_BUG_ON_PAGE(PageCgroupUsed(pc), page);
/*
@@ -2755,6 +2752,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
spin_unlock_irq(&zone->lru_lock);
}

+ local_irq_disable();
mem_cgroup_charge_statistics(memcg, page, nr_pages);
/*
* "charge_statistics" updated event counter. Then, check it.
@@ -2762,6 +2760,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
* if they exceeds softlimit.
*/
memcg_check_events(memcg, page);
+ local_irq_enable();
}

static DEFINE_MUTEX(set_limit_mutex);
@@ -3522,8 +3521,6 @@ static int mem_cgroup_move_account(struct page *page,
nr_pages);
}

- mem_cgroup_charge_statistics(from, page, -nr_pages);
-
/*
* It is safe to change pc->mem_cgroup here because the page
* is referenced, charged, and isolated - we can't race with
@@ -3532,14 +3529,15 @@ static int mem_cgroup_move_account(struct page *page,

/* caller should have done css_get */
pc->mem_cgroup = to;
- mem_cgroup_charge_statistics(to, page, nr_pages);
move_unlock_mem_cgroup(from, &flags);
ret = 0;
- /*
- * check events
- */
+
+ local_irq_disable();
+ mem_cgroup_charge_statistics(to, page, nr_pages);
memcg_check_events(to, page);
+ mem_cgroup_charge_statistics(from, page, -nr_pages);
memcg_check_events(from, page);
+ local_irq_enable();
out:
return ret;
}
@@ -3620,6 +3618,9 @@ out:

void mem_cgroup_uncharge_start(void)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
current->memcg_batch.do_batch++;
/* We can do nest. */
if (current->memcg_batch.do_batch == 1) {
@@ -3627,21 +3628,18 @@ void mem_cgroup_uncharge_start(void)
current->memcg_batch.nr_pages = 0;
current->memcg_batch.memsw_nr_pages = 0;
}
+ local_irq_restore(flags);
}

void mem_cgroup_uncharge_end(void)
{
struct memcg_batch_info *batch = &current->memcg_batch;
+ unsigned long flags;

- if (!batch->do_batch)
- return;
-
- batch->do_batch--;
- if (batch->do_batch) /* If stacked, do nothing. */
- return;
-
- if (!batch->memcg)
- return;
+ local_irq_save(flags);
+ VM_BUG_ON(!batch->do_batch);
+ if (--batch->do_batch) /* If stacked, do nothing */
+ goto out;
/*
* This "batch->memcg" is valid without any css_get/put etc...
* bacause we hide charges behind us.
@@ -3653,8 +3651,8 @@ void mem_cgroup_uncharge_end(void)
res_counter_uncharge(&batch->memcg->memsw,
batch->memsw_nr_pages * PAGE_SIZE);
memcg_oom_recover(batch->memcg);
- /* forget this pointer (for sanity check) */
- batch->memcg = NULL;
+out:
+ local_irq_restore(flags);
}

#ifdef CONFIG_MEMCG_SWAP
@@ -3912,7 +3910,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_mask, &nr_scanned);
nr_reclaimed += reclaimed;
*total_scanned += nr_scanned;
- spin_lock(&mctz->lock);
+ spin_lock_irq(&mctz->lock);

/*
* If we failed to reclaim anything from this memory cgroup
@@ -3952,7 +3950,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
*/
/* If excess == 0, no tree ops */
__mem_cgroup_insert_exceeded(mz, mctz, excess);
- spin_unlock(&mctz->lock);
+ spin_unlock_irq(&mctz->lock);
css_put(&mz->memcg->css);
loop++;
/*
@@ -6567,6 +6565,7 @@ void mem_cgroup_uncharge(struct page *page)
unsigned int nr_pages = 1;
struct mem_cgroup *memcg;
struct page_cgroup *pc;
+ unsigned long pc_flags;
unsigned long flags;

VM_BUG_ON_PAGE(PageLRU(page), page);
@@ -6591,35 +6590,38 @@ void mem_cgroup_uncharge(struct page *page)
* exclusive access to the page.
*/
memcg = pc->mem_cgroup;
- flags = pc->flags;
+ pc_flags = pc->flags;
pc->flags = 0;

- mem_cgroup_charge_statistics(memcg, page, -nr_pages);
- memcg_check_events(memcg, page);
+ local_irq_save(flags);

+ if (nr_pages > 1)
+ goto direct;
+ if (unlikely(test_thread_flag(TIF_MEMDIE)))
+ goto direct;
batch = &current->memcg_batch;
+ if (!batch->do_batch)
+ goto direct;
+ if (batch->memcg && batch->memcg != memcg)
+ goto direct;
if (!batch->memcg)
batch->memcg = memcg;
- else if (batch->memcg != memcg)
- goto uncharge;
- if (nr_pages > 1)
- goto uncharge;
- if (!batch->do_batch)
- goto uncharge;
- if (test_thread_flag(TIF_MEMDIE))
- goto uncharge;
- if (flags & PCG_MEM)
+ if (pc_flags & PCG_MEM)
batch->nr_pages++;
- if (flags & PCG_MEMSW)
+ if (pc_flags & PCG_MEMSW)
batch->memsw_nr_pages++;
- return;
-uncharge:
- if (flags & PCG_MEM)
+ goto out;
+direct:
+ if (pc_flags & PCG_MEM)
res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE);
- if (flags & PCG_MEMSW)
+ if (pc_flags & PCG_MEMSW)
res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE);
- if (batch->memcg != memcg)
- memcg_oom_recover(memcg);
+ memcg_oom_recover(memcg);
+out:
+ mem_cgroup_charge_statistics(memcg, page, -nr_pages);
+ memcg_check_events(memcg, page);
+
+ local_irq_restore(flags);
}

/**
--
2.0.0

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