From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stanislav Kinsbursky Subject: Re: [PATCH v4 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients Date: Tue, 20 Sep 2011 17:34:49 +0400 Message-ID: <4E789679.1060601@parallels.com> References: <20110920101031.9861.18444.stgit@localhost6.localdomain6> <20110920101341.9861.51453.stgit@localhost6.localdomain6> <4E788F8C.20103@netapp.com> <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD10@SACMVEXC2-PRD.hq.netapp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Schumaker, Bryan" , "linux-nfs@vger.kernel.org" , Pavel Emelianov , "neilb@suse.de" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "bfields@fieldses.org" , "davem@davemloft.net" To: "Myklebust, Trond" Return-path: In-Reply-To: <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD10@SACMVEXC2-PRD.hq.netapp.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 20.09.2011 17:15, Myklebust, Trond =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> -----Original Message----- >> From: Schumaker, Bryan >> Sent: Tuesday, September 20, 2011 9:05 AM >> To: Stanislav Kinsbursky >> Cc: Myklebust, Trond; linux-nfs@vger.kernel.org; xemul@parallels.com= ; >> neilb@suse.de; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; >> bfields@fieldses.org; davem@davemloft.net >> Subject: Re: [PATCH v4 1/8] SUNRPC: introduce helpers for reference >> counted rpcbind clients >> >> On 09/20/2011 06:13 AM, Stanislav Kinsbursky wrote: >>> This helpers will be used for dynamical creation and destruction of >>> rpcbind clients. >>> Variable rpcb_users is actually a counter of lauched RPC services. = If >>> rpcbind clients has been created already, then we just increase rpc= b_users. >>> >>> Signed-off-by: Stanislav Kinsbursky >>> >>> --- >>> net/sunrpc/rpcb_clnt.c | 50 >> ++++++++++++++++++++++++++++++++++++++++++++++++ >>> 1 files changed, 50 insertions(+), 0 deletions(-) >>> >>> diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c index >>> e45d2fb..8724780 100644 >>> --- a/net/sunrpc/rpcb_clnt.c >>> +++ b/net/sunrpc/rpcb_clnt.c >>> @@ -114,6 +114,9 @@ static struct rpc_program rpcb_program; >>> static struct rpc_clnt * rpcb_local_clnt; >>> static struct rpc_clnt * rpcb_local_clnt4; >>> >>> +DEFINE_SPINLOCK(rpcb_clnt_lock); >>> +unsigned int rpcb_users; >>> + >>> struct rpcbind_args { >>> struct rpc_xprt * r_xprt; >>> >>> @@ -161,6 +164,53 @@ static void rpcb_map_release(void *data) >>> kfree(map); >>> } >>> >>> +static int rpcb_get_local(void) >>> +{ >>> + spin_lock(&rpcb_clnt_lock); >>> + if (rpcb_users) >>> + rpcb_users++; >>> + spin_unlock(&rpcb_clnt_lock); >>> + >>> + return rpcb_users; >> ^^^^^^^^^^^^^^^^^^ >> Is it safe to use this variable outside of the rpcb_clnt_lock? >> > Nope. If rpcb_users was zero in the protected section above, nothing = guarantees that it will still be zero here, and so the caller may get t= he (wrong) impression that the counter was incremented. > Yep, you right. Will fix this races. >>> +} >>> + >>> +void rpcb_put_local(void) >>> +{ >>> + struct rpc_clnt *clnt =3D rpcb_local_clnt; >>> + struct rpc_clnt *clnt4 =3D rpcb_local_clnt4; >>> + int shutdown; >>> + >>> + spin_lock(&rpcb_clnt_lock); >>> + if (--rpcb_users =3D=3D 0) { >>> + rpcb_local_clnt =3D NULL; >>> + rpcb_local_clnt4 =3D NULL; >>> + } >>> + shutdown =3D !rpcb_users; >>> + spin_unlock(&rpcb_clnt_lock); >>> + >>> + if (shutdown) { >>> + /* >>> + * cleanup_rpcb_clnt - remove xprtsock's sysctls, unregister >>> + */ >>> + if (clnt4) >>> + rpc_shutdown_client(clnt4); >>> + if (clnt) >>> + rpc_shutdown_client(clnt); >>> + } >>> + return; >>> +} >>> + >>> +static void rpcb_set_local(struct rpc_clnt *clnt, struct rpc_clnt >>> +*clnt4) { >>> + /* Protected by rpcb_create_local_mutex */ > > Doesn't it need to be protected by rpcb_clnt_lock too? > Nope from my pow. It's protected by rpcb_create_local_mutex. I.e. no on= e will=20 change rpcb_users since it's zero. If it's non zero - we willn't get to= =20 rpcb_set_local(). >>> + rpcb_local_clnt =3D clnt; >>> + rpcb_local_clnt4 =3D clnt4; >>> + rpcb_users++; > ^^^^^^^^^^^^^^^^^^^ > >>> + dprintk("RPC: created new rpcb local clients (rpcb_local_cl= nt: " >>> + "%p, rpcb_local_clnt4: %p)\n", rpcb_local_clnt, >>> + rpcb_local_clnt4); >>> +} >>> + >>> /* >>> * Returns zero on success, otherwise a negative errno value >>> * is returned. >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-nfs= " >>> in the body of a message to majordomo@vger.kernel.org More >> majordomo >>> info at http://vger.kernel.org/majordomo-info.html > > =04=EF=BF=BD{.n=EF=BF=BD+=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BD= =EF=BF=BD=EF=BF=BD+%=EF=BF=BD=EF=BF=BDlzwm=EF=BF=BD=EF=BF=BDb=EF=BF=BD=EB= =A7=B2=EF=BF=BD=EF=BF=BDr=EF=BF=BD=EF=BF=BDzX=EF=BF=BD=EF=BF=BD=19=DF=B2= )=EF=BF=BD=EF=BF=BD=EF=BF=BDw*=1Fjg=EF=BF=BD=EF=BF=BD=EF=BF=BD=1E=EF=BF= =BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=DD=A2j/=EF=BF=BD=EF=BF=BD=EF=BF= =BDz=EF=BF=BD=DE=96=EF=BF=BD=EF=BF=BD2=EF=BF=BD=DE=99=EF=BF=BD=EF=BF=BD= =EF=BF=BD&=EF=BF=BD)=DF=A1=EF=BF=BDa=EF=BF=BD=EF=BF=BD=7F=EF=BF=BD=EF=BF= =BD=1E=EF=BF=BDG=EF=BF=BD=EF=BF=BD=EF=BF=BDh=EF=BF=BD=0F=EF=BF=BDj:+v=EF= =BF=BD=EF=BF=BD=EF=BF=BDw=EF=BF=BD=D9=A5 --=20 Best regards, Stanislav Kinsbursky