diff options
| author | Kevin Hao <haokexin@gmail.com> | 2014-12-03 20:05:57 +0800 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2015-03-18 09:26:38 -0400 |
| commit | 6f0c637f85eae331ca99a3ccca178e3ef8437929 (patch) | |
| tree | f99c6f0c5cff0fc0c59b7ff48b9c0346dfd564bd | |
| parent | b5f4a3d424b7b76bc89ef18569c402c14dbdeff0 (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>
| -rw-r--r-- | include/linux/netpoll.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index f3c7c24bec1c..5a77fc924892 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -86,9 +86,21 @@ static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb) #ifdef CONFIG_NETPOLL 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; + +#ifdef CONFIG_PREEMPT_RT_FULL + rcu_read_lock_bh(); +#endif + + npinfo = rcu_dereference_bh(skb->dev->npinfo); + ret = npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags); + +#ifdef CONFIG_PREEMPT_RT_FULL + rcu_read_unlock_bh(); +#endif - return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags); + return ret; } static inline bool netpoll_rx(struct sk_buff *skb) |