Message ID | 1425056838.5130.27.camel@edumazet-glaptop2.roam.corp.google.com |
---|---|
State | Superseded, archived |
Delegated to: | David Miller |
Headers | show |
On 02/27/2015 06:07 PM, Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > We did a failed attempt in the past to only use rcu in rtnl dump > operations (commit e67f88dd12f6 "net: dont hold rtnl mutex during > netlink dump callbacks") > > Now that dumps are holding RTNL anyway, there is no need to also > use rcu locking, as it forbids any scheduling ability, like > GFP_KERNEL allocations that controlling path should use instead > of GFP_ATOMIC whenever possible. > > This should fix following splat Cong Wang reported : > > =============================== [ Btw, I think patchwork has an issue with above line when fetching the mbox : it thinks commit description ends here. :( Prefixing with a space char should help to not get it lost. ] -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2015-02-27 at 18:19 +0100, Daniel Borkmann wrote: > On 02/27/2015 06:07 PM, Eric Dumazet wrote: > > From: Eric Dumazet <edumazet@google.com> > > > > We did a failed attempt in the past to only use rcu in rtnl dump > > operations (commit e67f88dd12f6 "net: dont hold rtnl mutex during > > netlink dump callbacks") > > > > Now that dumps are holding RTNL anyway, there is no need to also > > use rcu locking, as it forbids any scheduling ability, like > > GFP_KERNEL allocations that controlling path should use instead > > of GFP_ATOMIC whenever possible. > > > > This should fix following splat Cong Wang reported : > > > > =============================== > > [ Btw, I think patchwork has an issue with above line when fetching > the mbox : it thinks commit description ends here. :( > > Prefixing with a space char should help to not get it lost. ] Thanks Daniel for this hint, will send a v2. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Feb 27, 2015 at 9:19 AM, Daniel Borkmann <daniel@iogearbox.net> wrote: > On 02/27/2015 06:07 PM, Eric Dumazet wrote: >> >> From: Eric Dumazet <edumazet@google.com> >> >> We did a failed attempt in the past to only use rcu in rtnl dump >> operations (commit e67f88dd12f6 "net: dont hold rtnl mutex during >> netlink dump callbacks") >> >> Now that dumps are holding RTNL anyway, there is no need to also >> use rcu locking, as it forbids any scheduling ability, like >> GFP_KERNEL allocations that controlling path should use instead >> of GFP_ATOMIC whenever possible. >> >> This should fix following splat Cong Wang reported : >> >> =============================== > > > [ Btw, I think patchwork has an issue with above line when fetching > the mbox : it thinks commit description ends here. :( > > Prefixing with a space char should help to not get it lost. ] To save everyone's time, either fix patchwork or teach checkpatch. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
=============================== [ INFO: suspicious RCU usage. ] 3.19.0+ #805 Tainted: G W ------------------------------- include/linux/rcupdate.h:538 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 2 locks held by ip/771: #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff8182b8f4>] netlink_dump+0x21/0x26c #1: (rcu_read_lock){......}, at: [<ffffffff817d785b>] rcu_read_lock+0x0/0x6e stack backtrace: CPU: 3 PID: 771 Comm: ip Tainted: G W 3.19.0+ #805 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 0000000000000001 ffff8800d51e7718 ffffffff81a27457 0000000029e729e6 ffff8800d6108000 ffff8800d51e7748 ffffffff810b539b ffffffff820013dd 00000000000001c8 0000000000000000 ffff8800d7448088 ffff8800d51e7758 Call Trace: [<ffffffff81a27457>] dump_stack+0x4c/0x65 [<ffffffff810b539b>] lockdep_rcu_suspicious+0x107/0x110 [<ffffffff8109796f>] rcu_preempt_sleep_check+0x45/0x47 [<ffffffff8109e457>] ___might_sleep+0x1d/0x1cb [<ffffffff8109e67d>] __might_sleep+0x78/0x80 [<ffffffff814b9b1f>] idr_alloc+0x45/0xd1 [<ffffffff810cb7ab>] ? rcu_read_lock_held+0x3b/0x3d [<ffffffff814b9f9d>] ? idr_for_each+0x53/0x101 [<ffffffff817c1383>] alloc_netid+0x61/0x69 [<ffffffff817c14c3>] __peernet2id+0x79/0x8d [<ffffffff817c1ab7>] peernet2id+0x13/0x1f [<ffffffff817d8673>] rtnl_fill_ifinfo+0xa8d/0xc20 [<ffffffff810b17d9>] ? __lock_is_held+0x39/0x52 [<ffffffff817d894f>] rtnl_dump_ifinfo+0x149/0x213 [<ffffffff8182b9c2>] netlink_dump+0xef/0x26c [<ffffffff8182bcba>] netlink_recvmsg+0x17b/0x2c5 [<ffffffff817b0adc>] __sock_recvmsg+0x4e/0x59 [<ffffffff817b1b40>] sock_recvmsg+0x3f/0x51 [<ffffffff817b1f9a>] ___sys_recvmsg+0xf6/0x1d9 [<ffffffff8115dc67>] ? handle_pte_fault+0x6e1/0xd3d [<ffffffff8100a3a0>] ? native_sched_clock+0x35/0x37 [<ffffffff8109f45b>] ? sched_clock_local+0x12/0x72 [<ffffffff8109f6ac>] ? sched_clock_cpu+0x9e/0xb7 [<ffffffff810cb7ab>] ? rcu_read_lock_held+0x3b/0x3d [<ffffffff811abde8>] ? __fcheck_files+0x4c/0x58 [<ffffffff811ac556>] ? __fget_light+0x2d/0x52 [<ffffffff817b376f>] __sys_recvmsg+0x42/0x60 [<ffffffff817b379f>] SyS_recvmsg+0x12/0x1c Signed-off-by: Eric Dumazet <edumazet@google.com> Fixes: commit 0c7aecd4bde4b7302 ("netns: add rtnl cmd to add and get peer netns ids") Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com> Reported-by: Cong Wang <xiyou.wangcong@gmail.com> --- net/core/rtnetlink.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 1385de0fa080..74ce25d2cded 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -1300,7 +1300,6 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) s_h = cb->args[0]; s_idx = cb->args[1]; - rcu_read_lock(); cb->seq = net->dev_base_seq; /* A hack to preserve kernel<->userspace interface. @@ -1322,7 +1321,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) { idx = 0; head = &net->dev_index_head[h]; - hlist_for_each_entry_rcu(dev, head, index_hlist) { + hlist_for_each_entry(dev, head, index_hlist) { if (idx < s_idx) goto cont; err = rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK, @@ -1344,7 +1343,6 @@ cont: } } out: - rcu_read_unlock(); cb->args[1] = idx; cb->args[0] = h;
From: Eric Dumazet <edumazet@google.com> We did a failed attempt in the past to only use rcu in rtnl dump operations (commit e67f88dd12f6 "net: dont hold rtnl mutex during netlink dump callbacks") Now that dumps are holding RTNL anyway, there is no need to also use rcu locking, as it forbids any scheduling ability, like GFP_KERNEL allocations that controlling path should use instead of GFP_ATOMIC whenever possible. This should fix following splat Cong Wang reported : -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html