Hi folks, In setting up a socket, there are two functions I make use of that in turn wind up calling static_key_slow_inc: setup_udp_tunnel_sock and sk_set_memalloc. These both make use of static_key_slow_inc because they selectively enable certain important code paths.
This is all fine, except it poses some problems when calling these functions inside of .ndo_open. In that case, I get ugly (debug) warnings like this: WARNING: CPU: 1 PID: 2002 at kernel/locking/mutex.c:526 mutex_lock_nested+0x39b/0x3b0() DEBUG_LOCKS_WARN_ON(in_interrupt()) [<ffffffff81621d0e>] dump_stack+0x45/0x57 [<ffffffff810505ca>] warn_slowpath_common+0x8a/0xc0 [<ffffffff81050655>] warn_slowpath_fmt+0x55/0x70 [<ffffffff8162513b>] mutex_lock_nested+0x39b/0x3b0 [<ffffffff8113d699>] static_key_slow_inc+0x59/0xc0 [<ffffffff8154ebc0>] udp_encap_enable+0x20/0x30 [<ffffffff8157a885>] setup_udp_tunnel_sock+0x55/0x70 [<ffffffff816028ac>] socket_init+0x1cc/0x3a0 [<ffffffff81600341>] open+0x21/0x1b0 [<ffffffff81476af0>] __dev_open+0xb0/0x110 [<ffffffff81476e01>] __dev_change_flags+0xa1/0x160 [<ffffffff81476ee9>] dev_change_flags+0x29/0x70 [<ffffffff8148652a>] do_setlink+0x5da/0xa80 [<ffffffff81487bed>] rtnl_newlink+0x50d/0x8a0 [<ffffffff81485141>] rtnetlink_rcv_msg+0xa1/0x240 [<ffffffff8149f1fb>] netlink_rcv_skb+0x9b/0xc0 [<ffffffff8148508e>] rtnetlink_rcv+0x2e/0x40 [<ffffffff8149ec3f>] netlink_unicast+0x16f/0x200 [<ffffffff8149f009>] netlink_sendmsg+0x339/0x380 [<ffffffff814559d9>] ___sys_sendmsg+0x2f9/0x310 [<ffffffff814566d7>] __sys_sendmsg+0x57/0xa0 [<ffffffff81456732>] SyS_sendmsg+0x12/0x20 [<ffffffff816295b2>] entry_SYSCALL_64_fastpath+0x16/0x7a The reason is that the static key code makes use of mutexes. And the mutex debug code ensures that in_interrupt() is zero; otherwise it prints that warning. In this case, in_interrupt() has a value of 512. So, questions: 1. Is the best thing to do just move my socket creation routine into a workqueue, and avoid this issue all together? 2. Is it, in fact, incorrect to check for in_interrupt(), and the debug assertion is actually wrong? 3. Is it a bug that in_interrupt() is returning non-zero in relation to a syscall? Thanks, Jason -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
