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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>
This commit is contained in:
Kevin Hao 2014-12-03 20:05:57 +08:00 committed by Alibek Omarov
parent f13b372196
commit 085ce53a6b
1 changed files with 14 additions and 2 deletions
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16
include/linux/netpoll.h
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@ -87,9 +87,21 @@ 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;
return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
#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 ret;
}
static inline bool netpoll_rx(struct sk_buff *skb)