Date: Wed, 19 Dec 2012 13:01:35 -0800 From: Vijay Singh <vijju.singh@gmail.com> To: Navdeep Parhar <nparhar@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: use of V_tcbinfo lock for TCP syncache Message-ID: <CALCNsJS8j0wvv4dc1Q6rLckmr0RE%2BgW0%2BmUDdmSvyfjXzKugsQ@mail.gmail.com> In-Reply-To: <50D21C3B.8020803@gmail.com> References: <CALCNsJRFyQ9ZmfJ3quX2-cUuFHjs2rXw63Tq5ZH-uP1%2BoQmjLw@mail.gmail.com> <50D218BA.7080301@FreeBSD.org> <50D21C3B.8020803@gmail.com>
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>> Holding the pcbinfo lock prevents races between syncache_socket() and >> accept(). See rwatson's comment just above tcp_usr_accept. I noted >> this too (the comment above tod->tod_offload_socket() in tcp_syncache.c) >> back when I updated the TOE code in the kernel. > > er, I think I told you why tcp_usr_accept holds the pcbinfo lock, which > wasn't your original question... :-) But it helped. So I am thinking about trying a change where syncache_socket() would call soalloc() first, get a socket, setup the inp, and then do a (modified) sonewconn to place the socket in the listener's queue. Robert's comment indicated that this would be a better way to eliminate the race since we wouldn't need the pcblock when we make the sonewconn call. -vijay
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