lkml.org 
[lkml]   [2020]   [Mar]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2] ipv4: fix a RCU-list lock in fib_triestat_seq_show
From
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.

\
 
 \ /
  Last update: 2020-03-27 04:27    [W:0.052 / U:18.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site