[PATCH v3] mm/slab: Annotate kmem_cache_node->list_lock as raw

From: Jiri Kosina
Date: Fri Oct 21 2022 - 15:18:25 EST

From: Jiri Kosina <jkosina@xxxxxxx>

The list_lock can be taken in hardirq context when do_drain() is being
called via IPI on all cores, and therefore lockdep complains about it,
because it can't be preempted on PREEMPT_RT.

That's not a real issue, as SLAB can't be built on PREEMPT_RT anyway, but
we still want to get rid of the warning on non-PREEMPT_RT builds.

Annotate it therefore as a raw lock in order to get rid of he lockdep
warning below.

=============================
[ BUG: Invalid wait context ]
6.1.0-rc1-00134-ge35184f32151 #4 Not tainted
-----------------------------
swapper/3/0 is trying to lock:
ffff8bc88086dc18 (&parent->list_lock){..-.}-{3:3}, at: do_drain+0x57/0xb0
other info that might help us debug this:
context-{2:2}
no locks held by swapper/3/0.
stack backtrace:
CPU: 3 PID: 0 Comm: swapper/3 Not tainted 6.1.0-rc1-00134-ge35184f32151 #4
Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
Call Trace:
<IRQ>
dump_stack_lvl+0x6b/0x9d
__lock_acquire+0x1519/0x1730
? build_sched_domains+0x4bd/0x1590
? __lock_acquire+0xad2/0x1730
lock_acquire+0x294/0x340
? do_drain+0x57/0xb0
? sched_clock_tick+0x41/0x60
_raw_spin_lock+0x2c/0x40
? do_drain+0x57/0xb0
do_drain+0x57/0xb0
__flush_smp_call_function_queue+0x138/0x220
__sysvec_call_function+0x4f/0x210
sysvec_call_function+0x4b/0x90
</IRQ>
<TASK>
asm_sysvec_call_function+0x16/0x20
RIP: 0010:mwait_idle+0x5e/0x80
Code: 31 d2 65 48 8b 04 25 80 ed 01 00 48 89 d1 0f 01 c8 48 8b 00 a8 08 75 14 66 90 0f 00 2d 0b 78 46 00 31 c0 48 89 c1 fb 0f 01 c9 <eb> 06 fb 0f 1f 44 00 00 65 48 8b 04 25 80 ed 01 00 f0 80 60 02 df
RSP: 0000:ffffa90940217ee0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9bb9f93a
RBP: 0000000000000003 R08: 0000000000000001 R09: 0000000000000001
R10: ffffa90940217ea8 R11: 0000000000000000 R12: ffffffffffffffff
R13: 0000000000000000 R14: ffff8bc88127c500 R15: 0000000000000000
? default_idle_call+0x1a/0xa0
default_idle_call+0x4b/0xa0
do_idle+0x1f1/0x2c0
? _raw_spin_unlock_irqrestore+0x56/0x70
cpu_startup_entry+0x19/0x20
start_secondary+0x122/0x150
secondary_startup_64_no_verify+0xce/0xdb
</TASK>

Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
---

v1->v2: fix !SLAB build failures due to list_lock mismatch
v2->v3: really fix it by sending refreshed version of the patch (facepalm)

mm/slab.c | 90 +++++++++++++++++++++++++++----------------------------
mm/slab.h | 4 +++
2 files changed, 49 insertions(+), 45 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 59c8e28f7b6a..d8a287900193 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -234,7 +234,7 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent)
parent->shared = NULL;
parent->alien = NULL;
parent->colour_next = 0;
- spin_lock_init(&parent->list_lock);
+ raw_spin_lock_init(&parent->list_lock);
parent->free_objects = 0;
parent->free_touched = 0;
}
@@ -559,9 +559,9 @@ static noinline void cache_free_pfmemalloc(struct kmem_cache *cachep,
slab_node = slab_nid(slab);
n = get_node(cachep, slab_node);

- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
free_block(cachep, &objp, 1, slab_node, &list);
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);

slabs_destroy(cachep, &list);
}
@@ -684,7 +684,7 @@ static void __drain_alien_cache(struct kmem_cache *cachep,
struct kmem_cache_node *n = get_node(cachep, node);

if (ac->avail) {
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
/*
* Stuff objects into the remote nodes shared array first.
* That way we could avoid the overhead of putting the objects
@@ -695,7 +695,7 @@ static void __drain_alien_cache(struct kmem_cache *cachep,

free_block(cachep, ac->entry, ac->avail, node, list);
ac->avail = 0;
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
}
}

@@ -768,9 +768,9 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
slabs_destroy(cachep, &list);
} else {
n = get_node(cachep, slab_node);
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
free_block(cachep, &objp, 1, slab_node, &list);
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
slabs_destroy(cachep, &list);
}
return 1;
@@ -811,10 +811,10 @@ static int init_cache_node(struct kmem_cache *cachep, int node, gfp_t gfp)
*/
n = get_node(cachep, node);
if (n) {
- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
n->free_limit = (1 + nr_cpus_node(node)) * cachep->batchcount +
cachep->num;
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);

return 0;
}
@@ -893,7 +893,7 @@ static int setup_kmem_cache_node(struct kmem_cache *cachep,
goto fail;

n = get_node(cachep, node);
- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
if (n->shared && force_change) {
free_block(cachep, n->shared->entry,
n->shared->avail, node, &list);
@@ -911,7 +911,7 @@ static int setup_kmem_cache_node(struct kmem_cache *cachep,
new_alien = NULL;
}

- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
slabs_destroy(cachep, &list);

/*
@@ -950,7 +950,7 @@ static void cpuup_canceled(long cpu)
if (!n)
continue;

- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);

/* Free limit for this kmem_cache_node */
n->free_limit -= cachep->batchcount;
@@ -961,7 +961,7 @@ static void cpuup_canceled(long cpu)
nc->avail = 0;

if (!cpumask_empty(mask)) {
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
goto free_slab;
}

@@ -975,7 +975,7 @@ static void cpuup_canceled(long cpu)
alien = n->alien;
n->alien = NULL;

- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);

kfree(shared);
if (alien) {
@@ -1159,7 +1159,7 @@ static void __init init_list(struct kmem_cache *cachep, struct kmem_cache_node *
/*
* Do not assume that spinlocks can be initialized via memcpy:
*/
- spin_lock_init(&ptr->list_lock);
+ raw_spin_lock_init(&ptr->list_lock);

MAKE_ALL_LISTS(cachep, ptr, nodeid);
cachep->node[nodeid] = ptr;
@@ -1330,11 +1330,11 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
for_each_kmem_cache_node(cachep, node, n) {
unsigned long total_slabs, free_slabs, free_objs;

- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);
total_slabs = n->total_slabs;
free_slabs = n->free_slabs;
free_objs = n->free_objects;
- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);

pr_warn(" node %d: slabs: %ld/%ld, objs: %ld/%ld\n",
node, total_slabs - free_slabs, total_slabs,
@@ -2096,7 +2096,7 @@ static void check_spinlock_acquired(struct kmem_cache *cachep)
{
#ifdef CONFIG_SMP
check_irq_off();
- assert_spin_locked(&get_node(cachep, numa_mem_id())->list_lock);
+ assert_raw_spin_locked(&get_node(cachep, numa_mem_id())->list_lock);
#endif
}

@@ -2104,7 +2104,7 @@ static void check_spinlock_acquired_node(struct kmem_cache *cachep, int node)
{
#ifdef CONFIG_SMP
check_irq_off();
- assert_spin_locked(&get_node(cachep, node)->list_lock);
+ assert_raw_spin_locked(&get_node(cachep, node)->list_lock);
#endif
}

@@ -2144,9 +2144,9 @@ static void do_drain(void *arg)
check_irq_off();
ac = cpu_cache_get(cachep);
n = get_node(cachep, node);
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
free_block(cachep, ac->entry, ac->avail, node, &list);
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
ac->avail = 0;
slabs_destroy(cachep, &list);
}
@@ -2164,9 +2164,9 @@ static void drain_cpu_caches(struct kmem_cache *cachep)
drain_alien_cache(cachep, n->alien);

for_each_kmem_cache_node(cachep, node, n) {
- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
drain_array_locked(cachep, n->shared, node, true, &list);
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);

slabs_destroy(cachep, &list);
}
@@ -2188,10 +2188,10 @@ static int drain_freelist(struct kmem_cache *cache,
nr_freed = 0;
while (nr_freed < tofree && !list_empty(&n->slabs_free)) {

- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
p = n->slabs_free.prev;
if (p == &n->slabs_free) {
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
goto out;
}

@@ -2204,7 +2204,7 @@ static int drain_freelist(struct kmem_cache *cache,
* to the cache.
*/
n->free_objects -= cache->num;
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
slab_destroy(cache, slab);
nr_freed++;
}
@@ -2629,7 +2629,7 @@ static void cache_grow_end(struct kmem_cache *cachep, struct slab *slab)
INIT_LIST_HEAD(&slab->slab_list);
n = get_node(cachep, slab_nid(slab));

- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
n->total_slabs++;
if (!slab->active) {
list_add_tail(&slab->slab_list, &n->slabs_free);
@@ -2639,7 +2639,7 @@ static void cache_grow_end(struct kmem_cache *cachep, struct slab *slab)

STATS_INC_GROWN(cachep);
n->free_objects += cachep->num - slab->active;
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);

fixup_objfreelist_debug(cachep, &list);
}
@@ -2805,7 +2805,7 @@ static struct slab *get_first_slab(struct kmem_cache_node *n, bool pfmemalloc)
{
struct slab *slab;

- assert_spin_locked(&n->list_lock);
+ assert_raw_spin_locked(&n->list_lock);
slab = list_first_entry_or_null(&n->slabs_partial, struct slab,
slab_list);
if (!slab) {
@@ -2832,10 +2832,10 @@ static noinline void *cache_alloc_pfmemalloc(struct kmem_cache *cachep,
if (!gfp_pfmemalloc_allowed(flags))
return NULL;

- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
slab = get_first_slab(n, true);
if (!slab) {
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
return NULL;
}

@@ -2844,7 +2844,7 @@ static noinline void *cache_alloc_pfmemalloc(struct kmem_cache *cachep,

fixup_slab_list(cachep, n, slab, &list);

- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
fixup_objfreelist_debug(cachep, &list);

return obj;
@@ -2903,7 +2903,7 @@ static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
if (!n->free_objects && (!shared || !shared->avail))
goto direct_grow;

- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
shared = READ_ONCE(n->shared);

/* See if we can refill from the shared array */
@@ -2927,7 +2927,7 @@ static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
must_grow:
n->free_objects -= ac->avail;
alloc_done:
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
fixup_objfreelist_debug(cachep, &list);

direct_grow:
@@ -3147,7 +3147,7 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
BUG_ON(!n);

check_irq_off();
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
slab = get_first_slab(n, false);
if (!slab)
goto must_grow;
@@ -3165,12 +3165,12 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,

fixup_slab_list(cachep, n, slab, &list);

- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
fixup_objfreelist_debug(cachep, &list);
return obj;

must_grow:
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
slab = cache_grow_begin(cachep, gfp_exact_node(flags), nodeid);
if (slab) {
/* This slab isn't counted yet so don't update free_objects */
@@ -3325,7 +3325,7 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)

check_irq_off();
n = get_node(cachep, node);
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
if (n->shared) {
struct array_cache *shared_array = n->shared;
int max = shared_array->limit - shared_array->avail;
@@ -3354,7 +3354,7 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
STATS_SET_FREEABLE(cachep, i);
}
#endif
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
ac->avail -= batchcount;
memmove(ac->entry, &(ac->entry[batchcount]), sizeof(void *)*ac->avail);
slabs_destroy(cachep, &list);
@@ -3721,9 +3721,9 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,

node = cpu_to_mem(cpu);
n = get_node(cachep, node);
- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
free_block(cachep, ac->entry, ac->avail, node, &list);
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
slabs_destroy(cachep, &list);
}
free_percpu(prev);
@@ -3815,9 +3815,9 @@ static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n,
return;
}

- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);
drain_array_locked(cachep, ac, node, false, &list);
- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);

slabs_destroy(cachep, &list);
}
@@ -3901,7 +3901,7 @@ void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo)

for_each_kmem_cache_node(cachep, node, n) {
check_irq_on();
- spin_lock_irq(&n->list_lock);
+ raw_spin_lock_irq(&n->list_lock);

total_slabs += n->total_slabs;
free_slabs += n->free_slabs;
@@ -3910,7 +3910,7 @@ void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo)
if (n->shared)
shared_avail += n->shared->avail;

- spin_unlock_irq(&n->list_lock);
+ raw_spin_unlock_irq(&n->list_lock);
}
num_objs = total_slabs * cachep->num;
active_slabs = total_slabs - free_slabs;
diff --git a/mm/slab.h b/mm/slab.h
index 0202a8c2f0d2..7a705e4228c8 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -750,7 +750,11 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s,
* The slab lists for all objects.
*/
struct kmem_cache_node {
+#ifdef CONFIG_SLAB
+ raw_spinlock_t list_lock;
+#else
spinlock_t list_lock;
+#endif

#ifdef CONFIG_SLAB
struct list_head slabs_partial; /* partial list first, better asm code */
--
2.35.3