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bpf: avoid hashtab deadlock with try_lock
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The commit 20b6cc3 ("bpf: Avoid hashtab deadlock with map_locked"),
try to fix deadlock, but in some case, the deadlock occurs:

* CPUn in task context with K1, and taking lock.
* CPUn interrupted by NMI context, with K2.
* They are using the same bucket, but different map_locked.

	    | Task
	    |
	+---v----+
	|  CPUn  |
	+---^----+
	    |
	    | NMI

Anyway, the lockdep still warn:
[   36.092222] ================================
[   36.092230] WARNING: inconsistent lock state
[   36.092234] 6.1.0-rc5+ #81 Tainted: G            E
[   36.092236] --------------------------------
[   36.092237] inconsistent {INITIAL USE} -> {IN-NMI} usage.
[   36.092238] perf/1515 [HC1[1]:SC0[0]:HE0:SE1] takes:
[   36.092242] ffff888341acd1a0 (&htab->lockdep_key){....}-{2:2}, at: htab_lock_bucket+0x4d/0x58
[   36.092253] {INITIAL USE} state was registered at:
[   36.092255]   mark_usage+0x1d/0x11d
[   36.092262]   __lock_acquire+0x3c9/0x6ed
[   36.092266]   lock_acquire+0x23d/0x29a
[   36.092270]   _raw_spin_lock_irqsave+0x43/0x7f
[   36.092274]   htab_lock_bucket+0x4d/0x58
[   36.092276]   htab_map_delete_elem+0x82/0xfb
[   36.092278]   map_delete_elem+0x156/0x1ac
[   36.092282]   __sys_bpf+0x138/0xb71
[   36.092285]   __do_sys_bpf+0xd/0x15
[   36.092288]   do_syscall_64+0x6d/0x84
[   36.092291]   entry_SYSCALL_64_after_hwframe+0x63/0xcd
[   36.092295] irq event stamp: 120346
[   36.092296] hardirqs last  enabled at (120345): [<ffffffff8180b97f>] _raw_spin_unlock_irq+0x24/0x39
[   36.092299] hardirqs last disabled at (120346): [<ffffffff81169e85>] generic_exec_single+0x40/0xb9
[   36.092303] softirqs last  enabled at (120268): [<ffffffff81c00347>] __do_softirq+0x347/0x387
[   36.092307] softirqs last disabled at (120133): [<ffffffff810ba4f0>] __irq_exit_rcu+0x67/0xc6
[   36.092311]
[   36.092311] other info that might help us debug this:
[   36.092312]  Possible unsafe locking scenario:
[   36.092312]
[   36.092313]        CPU0
[   36.092313]        ----
[   36.092314]   lock(&htab->lockdep_key);
[   36.092315]   <Interrupt>
[   36.092316]     lock(&htab->lockdep_key);
[   36.092318]
[   36.092318]  *** DEADLOCK ***
[   36.092318]
[   36.092318] 3 locks held by perf/1515:
[   36.092320]  #0: ffff8881b9805cc0 (&cpuctx_mutex){+.+.}-{4:4}, at: perf_event_ctx_lock_nested+0x8e/0xba
[   36.092327]  #1: ffff8881075ecc20 (&event->child_mutex){+.+.}-{4:4}, at: perf_event_for_each_child+0x35/0x76
[   36.092332]  #2: ffff8881b9805c20 (&cpuctx_lock){-.-.}-{2:2}, at: perf_ctx_lock+0x12/0x27
[   36.092339]
[   36.092339] stack backtrace:
[   36.092341] CPU: 0 PID: 1515 Comm: perf Tainted: G            E      6.1.0-rc5+ #81
[   36.092344] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[   36.092349] Call Trace:
[   36.092351]  <NMI>
[   36.092354]  dump_stack_lvl+0x57/0x81
[   36.092359]  lock_acquire+0x1f4/0x29a
[   36.092363]  ? handle_pmi_common+0x13f/0x1f0
[   36.092366]  ? htab_lock_bucket+0x4d/0x58
[   36.092371]  _raw_spin_lock_irqsave+0x43/0x7f
[   36.092374]  ? htab_lock_bucket+0x4d/0x58
[   36.092377]  htab_lock_bucket+0x4d/0x58
[   36.092379]  htab_map_update_elem+0x11e/0x220
[   36.092386]  bpf_prog_f3a535ca81a8128a_bpf_prog2+0x3e/0x42
[   36.092392]  trace_call_bpf+0x177/0x215
[   36.092398]  perf_trace_run_bpf_submit+0x52/0xaa
[   36.092403]  ? x86_pmu_stop+0x97/0x97
[   36.092407]  perf_trace_nmi_handler+0xb7/0xe0
[   36.092415]  nmi_handle+0x116/0x254
[   36.092418]  ? x86_pmu_stop+0x97/0x97
[   36.092423]  default_do_nmi+0x3d/0xf6
[   36.092428]  exc_nmi+0xa1/0x109
[   36.092432]  end_repeat_nmi+0x16/0x67
[   36.092436] RIP: 0010:wrmsrl+0xd/0x1b
[   36.092441] Code: 04 01 00 00 c6 84 07 48 01 00 00 01 5b e9 46 15 80 00 5b c3 cc cc cc cc c3 cc cc cc cc 48 89 f2 89 f9 89 f0 48 c1 ea 20 0f 30 <66> 90 c3 cc cc cc cc 31 d2 e9 2f 04 49 00 0f 1f 44 00 00 40 0f6
[   36.092443] RSP: 0018:ffffc900043dfc48 EFLAGS: 00000002
[   36.092445] RAX: 000000000000000f RBX: ffff8881b96153e0 RCX: 000000000000038f
[   36.092447] RDX: 0000000000000007 RSI: 000000070000000f RDI: 000000000000038f
[   36.092449] RBP: 000000070000000f R08: ffffffffffffffff R09: ffff8881053bdaa8
[   36.092451] R10: ffff8881b9805d40 R11: 0000000000000005 R12: ffff8881b9805c00
[   36.092452] R13: 0000000000000000 R14: 0000000000000000 R15: ffff8881075ec970
[   36.092460]  ? wrmsrl+0xd/0x1b
[   36.092465]  ? wrmsrl+0xd/0x1b
[   36.092469]  </NMI>
[   36.092469]  <TASK>
[   36.092470]  __intel_pmu_enable_all.constprop.0+0x7c/0xaf
[   36.092475]  event_function+0xb6/0xd3
[   36.092478]  ? cpu_to_node+0x1a/0x1a
[   36.092482]  ? cpu_to_node+0x1a/0x1a
[   36.092485]  remote_function+0x1e/0x4c
[   36.092489]  generic_exec_single+0x48/0xb9
[   36.092492]  ? __lock_acquire+0x666/0x6ed
[   36.092497]  smp_call_function_single+0xbf/0x106
[   36.092499]  ? cpu_to_node+0x1a/0x1a
[   36.092504]  ? kvm_sched_clock_read+0x5/0x11
[   36.092508]  ? __perf_event_task_sched_in+0x13d/0x13d
[   36.092513]  cpu_function_call+0x47/0x69
[   36.092516]  ? perf_event_update_time+0x52/0x52
[   36.092519]  event_function_call+0x89/0x117
[   36.092521]  ? __perf_event_task_sched_in+0x13d/0x13d
[   36.092526]  ? _perf_event_disable+0x4a/0x4a
[   36.092528]  perf_event_for_each_child+0x3d/0x76
[   36.092532]  ? _perf_event_disable+0x4a/0x4a
[   36.092533]  _perf_ioctl+0x564/0x590
[   36.092537]  ? __lock_release+0xd5/0x1b0
[   36.092543]  ? perf_event_ctx_lock_nested+0x8e/0xba
[   36.092547]  perf_ioctl+0x42/0x5f
[   36.092551]  vfs_ioctl+0x1e/0x2f
[   36.092554]  __do_sys_ioctl+0x66/0x89
[   36.092559]  do_syscall_64+0x6d/0x84
[   36.092563]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[   36.092566] RIP: 0033:0x7fe7110f362b
[   36.092569] Code: 0f 1e fa 48 8b 05 5d b8 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2d b8 2c 00 f7 d8 64 89 018
[   36.092570] RSP: 002b:00007ffebb8e4b08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[   36.092573] RAX: ffffffffffffffda RBX: 0000000000002400 RCX: 00007fe7110f362b
[   36.092575] RDX: 0000000000000000 RSI: 0000000000002400 RDI: 0000000000000013
[   36.092576] RBP: 00007ffebb8e4b40 R08: 0000000000000001 R09: 000055c1db4a5b40
[   36.092577] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[   36.092579] R13: 000055c1db3b2a30 R14: 0000000000000000 R15: 0000000000000000
[   36.092586]  </TASK>

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
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@xpu22
xpu22 authored and Kernel Patches Daemon committed Nov 21, 2022
1 parent afc863b commit ccd40e8
Showing 1 changed file with 36 additions and 60 deletions.
96 changes: 36 additions & 60 deletions kernel/bpf/hashtab.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -80,9 +80,6 @@ struct bucket {
raw_spinlock_t raw_lock;
};

#define HASHTAB_MAP_LOCK_COUNT 8
#define HASHTAB_MAP_LOCK_MASK (HASHTAB_MAP_LOCK_COUNT - 1)

struct bpf_htab {
struct bpf_map map;
struct bpf_mem_alloc ma;
Expand All @@ -104,7 +101,6 @@ struct bpf_htab {
u32 elem_size; /* size of each element in bytes */
u32 hashrnd;
struct lock_class_key lockdep_key;
int __percpu *map_locked[HASHTAB_MAP_LOCK_COUNT];
};

/* each htab element is struct htab_elem + key + value */
Expand Down Expand Up @@ -146,35 +142,26 @@ static void htab_init_buckets(struct bpf_htab *htab)
}
}

static inline int htab_lock_bucket(const struct bpf_htab *htab,
struct bucket *b, u32 hash,
static inline int htab_lock_bucket(struct bucket *b,
unsigned long *pflags)
{
unsigned long flags;

hash = hash & HASHTAB_MAP_LOCK_MASK;

preempt_disable();
if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) {
__this_cpu_dec(*(htab->map_locked[hash]));
preempt_enable();
return -EBUSY;
if (in_nmi()) {
if (!raw_spin_trylock_irqsave(&b->raw_lock, flags))
return -EBUSY;
} else {
raw_spin_lock_irqsave(&b->raw_lock, flags);
}

raw_spin_lock_irqsave(&b->raw_lock, flags);
*pflags = flags;

return 0;
}

static inline void htab_unlock_bucket(const struct bpf_htab *htab,
struct bucket *b, u32 hash,
static inline void htab_unlock_bucket(struct bucket *b,
unsigned long flags)
{
hash = hash & HASHTAB_MAP_LOCK_MASK;
raw_spin_unlock_irqrestore(&b->raw_lock, flags);
__this_cpu_dec(*(htab->map_locked[hash]));
preempt_enable();
}

static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
Expand Down Expand Up @@ -467,7 +454,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
struct bpf_htab *htab;
int err, i;
int err;

htab = bpf_map_area_alloc(sizeof(*htab), NUMA_NO_NODE);
if (!htab)
Expand Down Expand Up @@ -512,15 +499,6 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
if (!htab->buckets)
goto free_htab;

for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) {
htab->map_locked[i] = bpf_map_alloc_percpu(&htab->map,
sizeof(int),
sizeof(int),
GFP_USER);
if (!htab->map_locked[i])
goto free_map_locked;
}

if (htab->map.map_flags & BPF_F_ZERO_SEED)
htab->hashrnd = 0;
else
Expand Down Expand Up @@ -548,13 +526,13 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
if (htab->use_percpu_counter) {
err = percpu_counter_init(&htab->pcount, 0, GFP_KERNEL);
if (err)
goto free_map_locked;
goto free_buckets;
}

if (prealloc) {
err = prealloc_init(htab);
if (err)
goto free_map_locked;
goto free_buckets;

if (!percpu && !lru) {
/* lru itself can remove the least used element, so
Expand All @@ -567,24 +545,23 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
} else {
err = bpf_mem_alloc_init(&htab->ma, htab->elem_size, false);
if (err)
goto free_map_locked;
goto free_buckets;
if (percpu) {
err = bpf_mem_alloc_init(&htab->pcpu_ma,
round_up(htab->map.value_size, 8), true);
if (err)
goto free_map_locked;
goto free_buckets;
}
}

return &htab->map;

free_prealloc:
prealloc_destroy(htab);
free_map_locked:
free_buckets:
if (htab->use_percpu_counter)
percpu_counter_destroy(&htab->pcount);
for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
free_percpu(htab->map_locked[i]);

bpf_map_area_free(htab->buckets);
bpf_mem_alloc_destroy(&htab->pcpu_ma);
bpf_mem_alloc_destroy(&htab->ma);
Expand Down Expand Up @@ -781,7 +758,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
b = __select_bucket(htab, tgt_l->hash);
head = &b->head;

ret = htab_lock_bucket(htab, b, tgt_l->hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return false;

Expand All @@ -792,7 +769,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
break;
}

htab_unlock_bucket(htab, b, tgt_l->hash, flags);
htab_unlock_bucket(b, flags);

return l == tgt_l;
}
Expand Down Expand Up @@ -1106,7 +1083,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
*/
}

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand Down Expand Up @@ -1151,7 +1128,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
}
ret = 0;
err:
htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);
return ret;
}

Expand Down Expand Up @@ -1197,7 +1174,7 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
copy_map_value(&htab->map,
l_new->key + round_up(map->key_size, 8), value);

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand All @@ -1218,7 +1195,7 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
ret = 0;

err:
htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);

if (ret)
htab_lru_push_free(htab, l_new);
Expand Down Expand Up @@ -1254,7 +1231,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
b = __select_bucket(htab, hash);
head = &b->head;

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand All @@ -1279,7 +1256,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
}
ret = 0;
err:
htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);
return ret;
}

Expand Down Expand Up @@ -1320,7 +1297,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
return -ENOMEM;
}

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand All @@ -1344,7 +1321,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
}
ret = 0;
err:
htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);
if (l_new)
bpf_lru_push_free(&htab->lru, &l_new->lru_node);
return ret;
Expand Down Expand Up @@ -1383,7 +1360,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
b = __select_bucket(htab, hash);
head = &b->head;

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand All @@ -1396,7 +1373,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
ret = -ENOENT;
}

htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);
return ret;
}

Expand All @@ -1419,7 +1396,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
b = __select_bucket(htab, hash);
head = &b->head;

ret = htab_lock_bucket(htab, b, hash, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

Expand All @@ -1430,7 +1407,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
else
ret = -ENOENT;

htab_unlock_bucket(htab, b, hash, flags);
htab_unlock_bucket(b, flags);
if (l)
htab_lru_push_free(htab, l);
return ret;
Expand Down Expand Up @@ -1493,7 +1470,6 @@ static void htab_map_free_timers(struct bpf_map *map)
static void htab_map_free(struct bpf_map *map)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
int i;

/* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback.
* bpf_free_used_maps() is called after bpf prog is no longer executing.
Expand All @@ -1515,10 +1491,10 @@ static void htab_map_free(struct bpf_map *map)
bpf_map_area_free(htab->buckets);
bpf_mem_alloc_destroy(&htab->pcpu_ma);
bpf_mem_alloc_destroy(&htab->ma);

if (htab->use_percpu_counter)
percpu_counter_destroy(&htab->pcount);
for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
free_percpu(htab->map_locked[i]);

lockdep_unregister_key(&htab->lockdep_key);
bpf_map_area_free(htab);
}
Expand Down Expand Up @@ -1562,7 +1538,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
b = __select_bucket(htab, hash);
head = &b->head;

ret = htab_lock_bucket(htab, b, hash, &bflags);
ret = htab_lock_bucket(b, &bflags);
if (ret)
return ret;

Expand Down Expand Up @@ -1600,7 +1576,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
free_htab_elem(htab, l);
}

htab_unlock_bucket(htab, b, hash, bflags);
htab_unlock_bucket(b, bflags);

if (is_lru_map && l)
htab_lru_push_free(htab, l);
Expand Down Expand Up @@ -1718,7 +1694,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
head = &b->head;
/* do not grab the lock unless need it (bucket_cnt > 0). */
if (locked) {
ret = htab_lock_bucket(htab, b, batch, &flags);
ret = htab_lock_bucket(b, &flags);
if (ret) {
rcu_read_unlock();
bpf_enable_instrumentation();
Expand All @@ -1741,7 +1717,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
/* Note that since bucket_cnt > 0 here, it is implicit
* that the locked was grabbed, so release it.
*/
htab_unlock_bucket(htab, b, batch, flags);
htab_unlock_bucket(b, flags);
rcu_read_unlock();
bpf_enable_instrumentation();
goto after_loop;
Expand All @@ -1752,7 +1728,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
/* Note that since bucket_cnt > 0 here, it is implicit
* that the locked was grabbed, so release it.
*/
htab_unlock_bucket(htab, b, batch, flags);
htab_unlock_bucket(b, flags);
rcu_read_unlock();
bpf_enable_instrumentation();
kvfree(keys);
Expand Down Expand Up @@ -1813,7 +1789,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
dst_val += value_size;
}

htab_unlock_bucket(htab, b, batch, flags);
htab_unlock_bucket(b, flags);
locked = false;

while (node_to_free) {
Expand Down

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