On Fri, 2014-05-30 at 16:03 -0400, Neil Horman wrote: > On Fri, May 30, 2014 at 10:58:11AM -0700, Michael Chan wrote: > > On Fri, 2014-05-30 at 11:00 -0400, Neil Horman wrote: > > > The Cnic driver handles lots of ulp operations in its netdevice event > > > hanlder. > > > To do this, it accesses the ulp_ops array, which is an rcu protected > > > array. > > > However, some ulp operations (like bnx2fc_indicate_netevent) try to lock > > > mutexes, which might sleep (somthing that you can't do while holding rcu > > > read > > > side locks if you've configured non-preemptive rcu. > > > > > > Fix this by changing the dereference method. All accesses to the ulp_ops > > > array > > > for a cnic dev are modified under the protection of the rtnl lock, and so > > > we can > > > safely just use rcu_dereference_rtnl, and remove the rcu_read_lock here > > > > Because the bnx2fc function can sleep, we need a more complete fix to > > prevent the ulp_ops from going away when the device is unregistered. > > synchronize_rcu() won't be able to protect it. I'll post the patch > > later today. Thanks. > > > The device can't be unregistered while we hold rtnl, can it? Since we hold it > in this path it seems safe to me, even if we sleep, or am I missing something? > Neil > The netdev cannot be unregistered of course, but I am talking about bnx2fc unregistering the cnic device. For example if someone does fcoeadm -d or bnx2fc gets unloaded. >
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