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Date: Mon, 21 Nov 2022 18:05:21 +0800
From: xiangxia.m.yue@...il.com
To: unlisted-recipients:; (no To-header on input)
Cc: netdev@...r.kernel.org, Tonghao Zhang <xiangxia.m.yue@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>
Subject: [net-next] bpf: avoid hashtab deadlock with try_lock
From: Tonghao Zhang <xiangxia.m.yue@...il.com>
The commit 20b6cc34ea74 ("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@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Song Liu <song@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: KP Singh <kpsingh@...nel.org>
Cc: Stanislav Fomichev <sdf@...gle.com>
Cc: Hao Luo <haoluo@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
---
kernel/bpf/hashtab.c | 96 +++++++++++++++++---------------------------
1 file changed, 36 insertions(+), 60 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 22855d6ff6d3..429acd97c869 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -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;
@@ -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 */
@@ -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);
@@ -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)
@@ -513,15 +500,6 @@ 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
@@ -549,13 +527,13 @@ 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
@@ -568,12 +546,12 @@ 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;
}
}
@@ -581,11 +559,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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);
@@ -782,7 +759,7 @@ 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;
@@ -793,7 +770,7 @@ 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;
}
@@ -1107,7 +1084,7 @@ 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;
@@ -1152,7 +1129,7 @@ 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;
}
@@ -1198,7 +1175,7 @@ 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;
@@ -1219,7 +1196,7 @@ 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);
@@ -1255,7 +1232,7 @@ 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;
@@ -1280,7 +1257,7 @@ 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;
}
@@ -1321,7 +1298,7 @@ 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;
@@ -1345,7 +1322,7 @@ 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;
@@ -1384,7 +1361,7 @@ 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;
@@ -1397,7 +1374,7 @@ 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;
}
@@ -1420,7 +1397,7 @@ 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;
@@ -1431,7 +1408,7 @@ 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;
@@ -1494,7 +1471,6 @@ 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.
@@ -1517,10 +1493,10 @@ 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);
}
@@ -1564,7 +1540,7 @@ 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;
@@ -1602,7 +1578,7 @@ 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);
@@ -1720,7 +1696,7 @@ __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();
@@ -1743,7 +1719,7 @@ __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;
@@ -1754,7 +1730,7 @@ __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);
@@ -1815,7 +1791,7 @@ __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) {
--
2.27.0
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