From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manish Kumar Singh Subject: RE: [PATCH] bonding: avoid repeated display of same link status change Date: Mon, 22 Oct 2018 00:29:13 -0700 (PDT) Message-ID: <0548f1e3-1cc6-4194-99ff-20fb00205574@default> References: <20180917072059.32657-1-mk.singh@oracle.com> <33a66a80-22ed-d6b3-f6b2-4463357c5ffa@gmail.com> <78bf3185-fbd1-4a6c-ae32-70da0af2cbb4@default> <05f57c08-3ebb-7ee5-7ab2-519cb5a70bd8@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: Jay Vosburgh , Veaceslav Falico , Andy Gospodarek , "David S. Miller" , linux-kernel@vger.kernel.org To: Eric Dumazet , netdev@vger.kernel.org Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org > -----Original Message----- > From: Manish Kumar Singh > Sent: 24 =E0=A4=B8=E0=A4=BF=E0=A4=A4=E0=A4=AE=E0=A5=8D=E0=A4=AC=E0=A4=B0 = 2018 12:36 > To: Eric Dumazet; netdev@vger.kernel.org > Cc: Jay Vosburgh; Veaceslav Falico; Andy Gospodarek; David S. Miller; lin= ux- > kernel@vger.kernel.org > Subject: RE: [PATCH] bonding: avoid repeated display of same link status > change >=20 >=20 >=20 > > -----Original Message----- > > From: Eric Dumazet [mailto:eric.dumazet@gmail.com] > > Sent: 18 =E0=A4=B8=E0=A4=BF=E0=A4=A4=E0=A4=AE=E0=A5=8D=E0=A4=AC=E0=A4= =B0 2018 19:30 > > To: Manish Kumar Singh; Eric Dumazet; netdev@vger.kernel.org > > Cc: Jay Vosburgh; Veaceslav Falico; Andy Gospodarek; David S. Miller; l= inux- > > kernel@vger.kernel.org > > Subject: Re: [PATCH] bonding: avoid repeated display of same link statu= s > > change > > > > > > > > On 09/17/2018 10:05 PM, Manish Kumar Singh wrote: > > > > > > > > >> -----Original Message----- > > >> From: Eric Dumazet [mailto:eric.dumazet@gmail.com] > > >> Sent: 17 =E0=A4=B8=E0=A4=BF=E0=A4=A4=E0=A4=AE=E0=A5=8D=E0=A4=AC=E0= =A4=B0 2018 20:08 > > >> To: Manish Kumar Singh; netdev@vger.kernel.org > > >> Cc: Jay Vosburgh; Veaceslav Falico; Andy Gospodarek; David S. Miller= ; > > linux- > > >> kernel@vger.kernel.org > > >> Subject: Re: [PATCH] bonding: avoid repeated display of same link st= atus > > >> change > > >> > > >> > > >> > > >> On 09/17/2018 12:20 AM, mk.singh@oracle.com wrote: > > >>> From: Manish Kumar Singh > > >>> > > >>> When link status change needs to be committed and rtnl lock couldn'= t > be > > >>> taken, avoid redisplay of same link status change message. > > >>> > > >>> Signed-off-by: Manish Kumar Singh > > >>> --- > > >>> drivers/net/bonding/bond_main.c | 6 ++++-- > > >>> include/net/bonding.h | 1 + > > >>> 2 files changed, 5 insertions(+), 2 deletions(-) > > >>> > > >>> diff --git a/drivers/net/bonding/bond_main.c > > >> b/drivers/net/bonding/bond_main.c > > >>> index 217b790d22ed..fb4e3aff1677 100644 > > >>> --- a/drivers/net/bonding/bond_main.c > > >>> +++ b/drivers/net/bonding/bond_main.c > > >>> @@ -2087,7 +2087,7 @@ static int bond_miimon_inspect(struct > bonding > > >> *bond) > > >>> =09=09=09bond_propose_link_state(slave, BOND_LINK_FAIL); > > >>> =09=09=09commit++; > > >>> =09=09=09slave->delay =3D bond->params.downdelay; > > >>> -=09=09=09if (slave->delay) { > > >>> +=09=09=09if (slave->delay && !bond->rtnl_needed) { > > >>> =09=09=09=09netdev_info(bond->dev, "link status down > > for > > >> %sinterface %s, disabling it in %d ms\n", > > >>> =09=09=09=09=09 (BOND_MODE(bond) =3D=3D > > >>> =09=09=09=09=09 BOND_MODE_ACTIVEBACKUP) ? > > >>> @@ -2127,7 +2127,7 @@ static int bond_miimon_inspect(struct > bonding > > >> *bond) > > >>> =09=09=09commit++; > > >>> =09=09=09slave->delay =3D bond->params.updelay; > > >>> > > >>> -=09=09=09if (slave->delay) { > > >>> +=09=09=09if (slave->delay && !bond->rtnl_needed) { > > >>> =09=09=09=09netdev_info(bond->dev, "link status up for > > >> interface %s, enabling it in %d ms\n", > > >>> =09=09=09=09=09 slave->dev->name, > > >>> =09=09=09=09=09 ignore_updelay ? 0 : > > >>> @@ -2301,9 +2301,11 @@ static void bond_mii_monitor(struct > > >> work_struct *work) > > >>> =09=09if (!rtnl_trylock()) { > > >>> =09=09=09delay =3D 1; > > >>> =09=09=09should_notify_peers =3D false; > > >>> +=09=09=09bond->rtnl_needed =3D true; > > >> > > >> How can you set a shared variable with no synchronization ? > > > Thanks Eric for reviewing the patch. rtnl_needed is not a shared vari= able, > it > > is part of bonding structure, that is one per bonding driver instance. = There > > can't be two parallel instances of bond_miimon_inspect for a > single =C2=A0bonding > > driver instance at any given point of time. and only bond_miimon_inspec= t > > updates it. That=E2=80=99s why I think there is no need of any synchron= ization here. > > > > > > > > > > If rtnl_trylock() can not grab RTNL, > > there is no way the current thread can set the variable without a race= , if > the > > word including rtnl_needed is shared by other fields in the structure. > > > > Your patch adds a subtle possibility of future bugs, even if it runs fi= ne > today. > > > > Do not pave the way for future bugs, make your code robust, please. >=20 > Thankyou Eric, we are making the changes and will repost the patch after > testing it. > -Manish Please review the updated patch, I have changed the rtnl_needed to an atomi= c variable, to avoid any race condition: From: Manish Kumar Singh When link status change needs to be committed and rtnl lock couldn't be tak= en, avoid redisplay of same link status change message. Signed-off-by: Manish Kumar Singh --- drivers/net/bonding/bond_main.c | 6 ++++-- include/net/bonding.h | 1 + 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_mai= n.c index 217b790d22ed..fac5350bf19c 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2087,7 +2087,7 @@ static int bond_miimon_inspect(struct bonding *bond) =09=09=09bond_propose_link_state(slave, BOND_LINK_FAIL); =09=09=09commit++; =09=09=09slave->delay =3D bond->params.downdelay; -=09=09=09if (slave->delay) { +=09=09=09if (slave->delay && !atomic_read(&bond->rtnl_needed)) { =09=09=09=09netdev_info(bond->dev, "link status down for %sinterface %s, d= isabling it in %d ms\n", =09=09=09=09=09 (BOND_MODE(bond) =3D=3D =09=09=09=09=09 BOND_MODE_ACTIVEBACKUP) ? @@ -2127,7 +2127,7 @@ static int bond_miimon_inspect(struct bonding *bond) =09=09=09commit++; =09=09=09slave->delay =3D bond->params.updelay; =20 -=09=09=09if (slave->delay) { +=09=09=09if (slave->delay && !atomic_read(&bond->rtnl_needed)) { =09=09=09=09netdev_info(bond->dev, "link status up for interface %s, enabl= ing it in %d ms\n", =09=09=09=09=09 slave->dev->name, =09=09=09=09=09 ignore_updelay ? 0 : @@ -2301,9 +2301,11 @@ static void bond_mii_monitor(struct work_struct *wor= k) =09=09if (!rtnl_trylock()) { =09=09=09delay =3D 1; =09=09=09should_notify_peers =3D false; +=09=09=09atomic_set(&bond->rtnl_needed, 1); =09=09=09goto re_arm; =09=09} =20 +=09=09atomic_set(&bond->rtnl_needed, 0); =09=09bond_for_each_slave(bond, slave, iter) { =09=09=09bond_commit_link_state(slave, BOND_SLAVE_NOTIFY_LATER); =09=09} diff --git a/include/net/bonding.h b/include/net/bonding.h index 808f1d1673= 49..ffc1219f7a07 100644 --- a/include/net/bonding.h +++ b/include/net/bonding.h @@ -234,6 +234,7 @@ struct bonding { =09struct=09 dentry *debug_dir; #endif /* CONFIG_DEBUG_FS */ =09struct rtnl_link_stats64 bond_stats; +=09atomic_t rtnl_needed; }; =20 #define bond_slave_get_rcu(dev) \ -- 2.14.1 Thanks, Manish > > > > > > > > > > > > > >