diff options
authorKevin Hao <haokexin@gmail.com>2014-12-03 20:05:57 +0800
committerAnders Roxell <anders.roxell@linaro.org>2015-06-01 12:03:39 +0200
commit873c6bc22569e32fa14f6310599f9a42d172c1a7 (patch)
parentea60c8a4d0c5f0ad17fcf77032c8e86c18c41a2c (diff)
netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y
For vanilla kernel we don't need to invoke rcu_read_lock/unlock_bh explicitly to mark an RCU-bh critical section in the softirq context because bh is already disabled in this case. But for a rt kernel, the commit ("rcu: Merge RCU-bh into RCU-preempt") implements the RCU-bh in term of RCU-preempt. So we have to use rcu_read_lock/unlock_bh() to mark an RCU-bh critical section even in a softirq context. Otherwise we will get a call trace like this: include/linux/netpoll.h:90 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 1 lock held by irq/177-eth0_g0/129: #0: (&per_cpu(local_softirq_locks[i], __cpu).lock){+.+...}, at: [<8002f544>] do_current_softirqs+0x12c/0x5ec stack backtrace: CPU: 0 PID: 129 Comm: irq/177-eth0_g0 Not tainted 3.14.23 #11 [<80018c0c>] (unwind_backtrace) from [<800138b0>] (show_stack+0x20/0x24) [<800138b0>] (show_stack) from [<8075c3bc>] (dump_stack+0x84/0xd0) [<8075c3bc>] (dump_stack) from [<8008111c>] (lockdep_rcu_suspicious+0xe8/0x11c) [<8008111c>] (lockdep_rcu_suspicious) from [<805e94e8>] (dev_gro_receive+0x240/0x724) [<805e94e8>] (dev_gro_receive) from [<805e9c34>] (napi_gro_receive+0x3c/0x1e8) [<805e9c34>] (napi_gro_receive) from [<804b01ac>] (gfar_clean_rx_ring+0x2d4/0x624) [<804b01ac>] (gfar_clean_rx_ring) from [<804b078c>] (gfar_poll_rx_sq+0x58/0xe8) [<804b078c>] (gfar_poll_rx_sq) from [<805eada8>] (net_rx_action+0x1c8/0x418) [<805eada8>] (net_rx_action) from [<8002f62c>] (do_current_softirqs+0x214/0x5ec) [<8002f62c>] (do_current_softirqs) from [<8002fa88>] (__local_bh_enable+0x84/0x9c) [<8002fa88>] (__local_bh_enable) from [<8002fab8>] (local_bh_enable+0x18/0x1c) [<8002fab8>] (local_bh_enable) from [<80093924>] (irq_forced_thread_fn+0x50/0x74) [<80093924>] (irq_forced_thread_fn) from [<80093c30>] (irq_thread+0x158/0x1c4) [<80093c30>] (irq_thread) from [<800555b8>] (kthread+0xd4/0xe8) [<800555b8>] (kthread) from [<8000ee88>] (ret_from_fork+0x14/0x20) Signed-off-by: Kevin Hao <kexin.hao@windriver.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 files changed, 14 insertions, 2 deletions
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index fbfdb9d8d3a7..039dd5df0ef7 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -87,9 +87,21 @@ static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
static inline bool netpoll_rx_on(struct sk_buff *skb)
- struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
+ struct netpoll_info *npinfo;
+ bool ret;
+ rcu_read_lock_bh();
+ npinfo = rcu_dereference_bh(skb->dev->npinfo);
+ ret = npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+ rcu_read_unlock_bh();
- return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+ return ret;
static inline bool netpoll_rx(struct sk_buff *skb)