| Message ID | 20200325220100.7863-1-cai@lca.pw |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [v2] ipv4: fix a RCU-list lock in fib_triestat_seq_show | expand |
From: Qian Cai <cai@lca.pw> Date: Wed, 25 Mar 2020 18:01:00 -0400 > fib_triestat_seq_show() calls hlist_for_each_entry_rcu(tb, head, > tb_hlist) without rcu_read_lock() will trigger a warning, > > net/ipv4/fib_trie.c:2579 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by proc01/115277: > #0: c0000014507acf00 (&p->lock){+.+.}-{3:3}, at: seq_read+0x58/0x670 > > Call Trace: > dump_stack+0xf4/0x164 (unreliable) > lockdep_rcu_suspicious+0x140/0x164 > fib_triestat_seq_show+0x750/0x880 > seq_read+0x1a0/0x670 > proc_reg_read+0x10c/0x1b0 > __vfs_read+0x3c/0x70 > vfs_read+0xac/0x170 > ksys_read+0x7c/0x140 > system_call+0x5c/0x68 > > Fix it by adding a pair of rcu_read_lock/unlock() and use > cond_resched_rcu() to avoid the situation where walking of a large > number of items may prevent scheduling for a long time. > > Signed-off-by: Qian Cai <cai@lca.pw> Eric, please review.
On 3/26/20 8:27 PM, David Miller wrote: > From: Qian Cai <cai@lca.pw> > Date: Wed, 25 Mar 2020 18:01:00 -0400 >> Fix it by adding a pair of rcu_read_lock/unlock() and use >> cond_resched_rcu() to avoid the situation where walking of a large >> number of items may prevent scheduling for a long time. >> >> Signed-off-by: Qian Cai <cai@lca.pw> > > Eric, please review. > Patch looks good to me, thanks ! Reviewed-by: Eric Dumazet <edumazet@google.com>
From: Qian Cai <cai@lca.pw> Date: Wed, 25 Mar 2020 18:01:00 -0400 > fib_triestat_seq_show() calls hlist_for_each_entry_rcu(tb, head, > tb_hlist) without rcu_read_lock() will trigger a warning, > > net/ipv4/fib_trie.c:2579 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by proc01/115277: > #0: c0000014507acf00 (&p->lock){+.+.}-{3:3}, at: seq_read+0x58/0x670 > > Call Trace: > dump_stack+0xf4/0x164 (unreliable) > lockdep_rcu_suspicious+0x140/0x164 > fib_triestat_seq_show+0x750/0x880 > seq_read+0x1a0/0x670 > proc_reg_read+0x10c/0x1b0 > __vfs_read+0x3c/0x70 > vfs_read+0xac/0x170 > ksys_read+0x7c/0x140 > system_call+0x5c/0x68 > > Fix it by adding a pair of rcu_read_lock/unlock() and use > cond_resched_rcu() to avoid the situation where walking of a large > number of items may prevent scheduling for a long time. > > Signed-off-by: Qian Cai <cai@lca.pw> Applied and queued up for -stable, thanks.
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index ff0c24371e33..3be0affbabd3 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2577,6 +2577,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v) " %zd bytes, size of tnode: %zd bytes.\n", LEAF_SIZE, TNODE_SIZE(0)); + rcu_read_lock(); for (h = 0; h < FIB_TABLE_HASHSZ; h++) { struct hlist_head *head = &net->ipv4.fib_table_hash[h]; struct fib_table *tb; @@ -2596,7 +2597,9 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v) trie_show_usage(seq, t->stats); #endif } + cond_resched_rcu(); } + rcu_read_unlock(); return 0; }
fib_triestat_seq_show() calls hlist_for_each_entry_rcu(tb, head, tb_hlist) without rcu_read_lock() will trigger a warning, net/ipv4/fib_trie.c:2579 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by proc01/115277: #0: c0000014507acf00 (&p->lock){+.+.}-{3:3}, at: seq_read+0x58/0x670 Call Trace: dump_stack+0xf4/0x164 (unreliable) lockdep_rcu_suspicious+0x140/0x164 fib_triestat_seq_show+0x750/0x880 seq_read+0x1a0/0x670 proc_reg_read+0x10c/0x1b0 __vfs_read+0x3c/0x70 vfs_read+0xac/0x170 ksys_read+0x7c/0x140 system_call+0x5c/0x68 Fix it by adding a pair of rcu_read_lock/unlock() and use cond_resched_rcu() to avoid the situation where walking of a large number of items may prevent scheduling for a long time. Signed-off-by: Qian Cai <cai@lca.pw> --- Use cond_resched_rcu() from Eric. net/ipv4/fib_trie.c | 3 +++ 1 file changed, 3 insertions(+)