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Date: Wed, 1 Nov 2017 21:02:03 +0800 From: Jason Wang <jasowang@...hat.com> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, willemdebruijn.kernel@...il.com, tom@...bertland.com Subject: Re: [PATCH net-next V2 3/3] tun: add eBPF based queue selection method On 2017年11月01日 00:45, Michael S. Tsirkin wrote: >> +static void __tun_set_steering_ebpf(struct tun_struct *tun, >> + struct bpf_prog *new) >> +{ >> + struct bpf_prog *old; >> + >> + old = rtnl_dereference(tun->steering_prog); >> + rcu_assign_pointer(tun->steering_prog, new); >> + >> + if (old) { >> + synchronize_net(); >> + bpf_prog_destroy(old); >> + } >> +} >> + > Is this really called under rtnl? Yes it is __tun_chr_ioctl() will call rtnl_lock(). > If no then rtnl_dereference > is wrong. If yes I'm not sure you can call synchronize_net > under rtnl. > Are you worrying about the long wait? Looking at synchronize_net(), it does: void synchronize_net(void) { might_sleep(); if (rtnl_is_locked()) synchronize_rcu_expedited(); else synchronize_rcu(); } EXPORT_SYMBOL(synchronize_net); Thanks
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