* [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback
@ 2018-02-22 18:10 Yonghong Song
2018-02-22 18:18 ` Eric Dumazet
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Yonghong Song @ 2018-02-22 18:10 UTC (permalink / raw)
To: ast, daniel, edumazet, netdev; +Cc: kernel-team
Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
fixed a memory leak and removed unnecessary locks in map_free callback function.
Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on,
running tools/testing/selftests/bpf/test_lpm_map will have:
[ 98.294321] =============================
[ 98.294807] WARNING: suspicious RCU usage
[ 98.295359] 4.16.0-rc2+ #193 Not tainted
[ 98.295907] -----------------------------
[ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage!
[ 98.297657]
[ 98.297657] other info that might help us debug this:
[ 98.297657]
[ 98.298663]
[ 98.298663] rcu_scheduler_active = 2, debug_locks = 1
[ 98.299536] 2 locks held by kworker/2:1/54:
[ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
[ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
Since actual trie tree removal happens only after no other
accesses to the tree are possible, replacing
rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock))
with
rcu_dereference_protected(*slot, 1)
fixed the issue.
Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
Reported-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
kernel/bpf/lpm_trie.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
v1 -> v2:
. fix sparse warning which is introduced by v1, suggested by Eric.
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index a75e02c..b4b5b81 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -569,8 +569,7 @@ static void trie_free(struct bpf_map *map)
slot = &trie->root;
for (;;) {
- node = rcu_dereference_protected(*slot,
- lockdep_is_held(&trie->lock));
+ node = rcu_dereference_protected(*slot, 1);
if (!node)
goto out;
--
2.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback
2018-02-22 18:10 [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback Yonghong Song
@ 2018-02-22 18:18 ` Eric Dumazet
2018-02-22 18:49 ` David Miller
2018-02-22 20:30 ` Daniel Borkmann
2 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2018-02-22 18:18 UTC (permalink / raw)
To: Yonghong Song, ast, daniel, edumazet, netdev; +Cc: kernel-team
On Thu, 2018-02-22 at 10:10 -0800, Yonghong Song wrote:
> Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> fixed a memory leak and removed unnecessary locks in map_free callback function.
> Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on,
> running tools/testing/selftests/bpf/test_lpm_map will have:
>
> Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> Reported-by: Eric Dumazet <edumazet@google.com>
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
> kernel/bpf/lpm_trie.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> v1 -> v2:
> . fix sparse warning which is introduced by v1, suggested by Eric.
>
> diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
> index a75e02c..b4b5b81 100644
> --- a/kernel/bpf/lpm_trie.c
> +++ b/kernel/bpf/lpm_trie.c
> @@ -569,8 +569,7 @@ static void trie_free(struct bpf_map *map)
> slot = &trie->root;
>
> for (;;) {
> - node = rcu_dereference_protected(*slot,
> - lockdep_is_held(&trie->lock));
> + node = rcu_dereference_protected(*slot, 1);
> if (!node)
> goto out;
SGTM, thanks !
Reviewed-by: Eric Dumazet <edumazet@google.com>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback
2018-02-22 18:10 [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback Yonghong Song
2018-02-22 18:18 ` Eric Dumazet
@ 2018-02-22 18:49 ` David Miller
2018-02-22 20:30 ` Daniel Borkmann
2 siblings, 0 replies; 4+ messages in thread
From: David Miller @ 2018-02-22 18:49 UTC (permalink / raw)
To: yhs; +Cc: ast, daniel, edumazet, netdev, kernel-team
From: Yonghong Song <yhs@fb.com>
Date: Thu, 22 Feb 2018 10:10:35 -0800
> Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> fixed a memory leak and removed unnecessary locks in map_free callback function.
> Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on,
> running tools/testing/selftests/bpf/test_lpm_map will have:
>
> [ 98.294321] =============================
> [ 98.294807] WARNING: suspicious RCU usage
> [ 98.295359] 4.16.0-rc2+ #193 Not tainted
> [ 98.295907] -----------------------------
> [ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage!
> [ 98.297657]
> [ 98.297657] other info that might help us debug this:
> [ 98.297657]
> [ 98.298663]
> [ 98.298663] rcu_scheduler_active = 2, debug_locks = 1
> [ 98.299536] 2 locks held by kworker/2:1/54:
> [ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
> [ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
>
> Since actual trie tree removal happens only after no other
> accesses to the tree are possible, replacing
> rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock))
> with
> rcu_dereference_protected(*slot, 1)
> fixed the issue.
>
> Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> Reported-by: Eric Dumazet <edumazet@google.com>
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: David S. Miller <davem@davemloft.net>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback
2018-02-22 18:10 [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback Yonghong Song
2018-02-22 18:18 ` Eric Dumazet
2018-02-22 18:49 ` David Miller
@ 2018-02-22 20:30 ` Daniel Borkmann
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Borkmann @ 2018-02-22 20:30 UTC (permalink / raw)
To: Yonghong Song, ast, edumazet, netdev; +Cc: kernel-team
On 02/22/2018 07:10 PM, Yonghong Song wrote:
> Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> fixed a memory leak and removed unnecessary locks in map_free callback function.
> Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on,
> running tools/testing/selftests/bpf/test_lpm_map will have:
>
> [ 98.294321] =============================
> [ 98.294807] WARNING: suspicious RCU usage
> [ 98.295359] 4.16.0-rc2+ #193 Not tainted
> [ 98.295907] -----------------------------
> [ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage!
> [ 98.297657]
> [ 98.297657] other info that might help us debug this:
> [ 98.297657]
> [ 98.298663]
> [ 98.298663] rcu_scheduler_active = 2, debug_locks = 1
> [ 98.299536] 2 locks held by kworker/2:1/54:
> [ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
> [ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
>
> Since actual trie tree removal happens only after no other
> accesses to the tree are possible, replacing
> rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock))
> with
> rcu_dereference_protected(*slot, 1)
> fixed the issue.
>
> Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
> Reported-by: Eric Dumazet <edumazet@google.com>
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
Applied to bpf tree, thanks everyone!
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-02-22 20:30 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2018-02-22 18:10 [PATCH bpf v2] bpf: fix rcu lockdep warning for lpm_trie map_free callback Yonghong Song
2018-02-22 18:18 ` Eric Dumazet
2018-02-22 18:49 ` David Miller
2018-02-22 20:30 ` Daniel Borkmann
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