From: Vladimir Oltean <olteanv@gmail.com> To: Jakub Kicinski <kuba@kernel.org>, "David S. Miller" <davem@davemloft.net> Cc: Andrew Lunn <andrew@lunn.ch>, Vivien Didelot <vivien.didelot@gmail.com>, Florian Fainelli <f.fainelli@gmail.com>, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bridge@lists.linux-foundation.org, Roopa Prabhu <roopa@nvidia.com>, Nikolay Aleksandrov <nikolay@nvidia.com>, Jiri Pirko <jiri@resnulli.us>, Ido Schimmel <idosch@idosch.org>, Claudiu Manoil <claudiu.manoil@nxp.com>, Alexandre Belloni <alexandre.belloni@bootlin.com>, UNGLinuxDriver@microchip.com, Vadym Kochan <vkochan@marvell.com>, Taras Chornyi <tchornyi@marvell.com>, Grygorii Strashko <grygorii.strashko@ti.com>, Ioana Ciornei <ioana.ciornei@nxp.com>, Ivan Vecera <ivecera@redhat.com>, linux-omap@vger.kernel.org Subject: [PATCH v3 net-next 08/11] net: bridge: put SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS on the blocking call chain Date: Wed, 10 Feb 2021 11:14:42 +0200 [thread overview] Message-ID: <20210210091445.741269-9-olteanv@gmail.com> (raw) In-Reply-To: <20210210091445.741269-1-olteanv@gmail.com> From: Vladimir Oltean <vladimir.oltean@nxp.com> Since we would like br_switchdev_set_port_flag to not use an atomic notifier, it should be called from outside spinlock context. We can temporarily drop br->lock, but that creates some concurrency complications (example below is given for sysfs): - There might be an "echo 1 > multicast_flood" simultaneous with an "echo 0 > multicast_flood". The result of this is nondeterministic either way, so I'm not too concerned as long as the result is consistent (no other flags have changed). - There might be an "echo 1 > multicast_flood" simultaneous with an "echo 0 > learning". My expectation is that none of the two writes are "eaten", and the final flags contain BR_MCAST_FLOOD=1 and BR_LEARNING=0 regardless of the order of execution. That is actually possible if, on the commit path, we don't do a trivial "p->flags = flags" which might overwrite bits outside of our mask, but instead we just change the flags corresponding to our mask. Now that br_switchdev_set_port_flag is never called from under br->lock, it runs in sleepable context. All switchdev drivers handle SWITCHDEV_PORT_ATTR_SET as both blocking and atomic, so no changes are needed on that front. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- Changes in v3: - Drop the br->lock around br_switchdev_set_port_flag in this patch, for both sysfs and netlink. - Only set/restore the masked bits in p->flags to avoid concurrency issues. Changes in v2: Patch is new. net/bridge/br_netlink.c | 10 +++++++--- net/bridge/br_switchdev.c | 5 ++--- net/bridge/br_sysfs_if.c | 22 ++++++++++++++-------- 3 files changed, 23 insertions(+), 14 deletions(-) diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index b7731614c036..8f09106966c4 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -869,7 +869,7 @@ static void br_set_port_flag(struct net_bridge_port *p, struct nlattr *tb[], static int br_setport(struct net_bridge_port *p, struct nlattr *tb[], struct netlink_ext_ack *extack) { - unsigned long old_flags, changed_mask; + unsigned long flags, old_flags, changed_mask; bool br_vlan_tunnel_old; int err; @@ -896,10 +896,14 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[], br_set_port_flag(p, tb, IFLA_BRPORT_ISOLATED, BR_ISOLATED); changed_mask = old_flags ^ p->flags; + flags = p->flags; - err = br_switchdev_set_port_flag(p, p->flags, changed_mask, extack); + spin_unlock_bh(&p->br->lock); + err = br_switchdev_set_port_flag(p, flags, changed_mask, extack); + spin_lock_bh(&p->br->lock); if (err) { - p->flags = old_flags; + p->flags &= ~changed_mask; + p->flags |= (old_flags & changed_mask); goto out; } diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c index dbd94156960f..a79164ee65b9 100644 --- a/net/bridge/br_switchdev.c +++ b/net/bridge/br_switchdev.c @@ -79,9 +79,8 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p, attr.u.brport_flags.val = flags & mask; attr.u.brport_flags.mask = mask; - /* We run from atomic context here */ - err = call_switchdev_notifiers(SWITCHDEV_PORT_ATTR_SET, p->dev, - &info.info, extack); + err = call_switchdev_blocking_notifiers(SWITCHDEV_PORT_ATTR_SET, p->dev, + &info.info, extack); err = notifier_to_errno(err); if (err == -EOPNOTSUPP) return 0; diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c index 72e92376eef1..3f21fdd1cdaa 100644 --- a/net/bridge/br_sysfs_if.c +++ b/net/bridge/br_sysfs_if.c @@ -68,16 +68,22 @@ static int store_flag(struct net_bridge_port *p, unsigned long v, else flags &= ~mask; - if (flags != p->flags) { - err = br_switchdev_set_port_flag(p, flags, mask, &extack); - if (err) { - netdev_err(p->dev, "%s\n", extack._msg); - return err; - } + if (flags == p->flags) + return 0; - p->flags = flags; - br_port_flags_change(p, mask); + spin_unlock_bh(&p->br->lock); + err = br_switchdev_set_port_flag(p, flags, mask, &extack); + spin_lock_bh(&p->br->lock); + if (err) { + netdev_err(p->dev, "%s\n", extack._msg); + return err; } + + p->flags &= ~mask; + p->flags |= (flags & mask); + + br_port_flags_change(p, mask); + return 0; } -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Vladimir Oltean <olteanv@gmail.com> To: Jakub Kicinski <kuba@kernel.org>, "David S. Miller" <davem@davemloft.net> Cc: Ivan Vecera <ivecera@redhat.com>, Andrew Lunn <andrew@lunn.ch>, Alexandre Belloni <alexandre.belloni@bootlin.com>, Florian Fainelli <f.fainelli@gmail.com>, Jiri Pirko <jiri@resnulli.us>, Vadym Kochan <vkochan@marvell.com>, netdev@vger.kernel.org, bridge@lists.linux-foundation.org, Ioana Ciornei <ioana.ciornei@nxp.com>, linux-kernel@vger.kernel.org, UNGLinuxDriver@microchip.com, Taras Chornyi <tchornyi@marvell.com>, Ido Schimmel <idosch@idosch.org>, Claudiu Manoil <claudiu.manoil@nxp.com>, Grygorii Strashko <grygorii.strashko@ti.com>, Nikolay Aleksandrov <nikolay@nvidia.com>, Roopa Prabhu <roopa@nvidia.com>, linux-omap@vger.kernel.org, Vivien Didelot <vivien.didelot@gmail.com> Subject: [Bridge] [PATCH v3 net-next 08/11] net: bridge: put SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS on the blocking call chain Date: Wed, 10 Feb 2021 11:14:42 +0200 [thread overview] Message-ID: <20210210091445.741269-9-olteanv@gmail.com> (raw) In-Reply-To: <20210210091445.741269-1-olteanv@gmail.com> From: Vladimir Oltean <vladimir.oltean@nxp.com> Since we would like br_switchdev_set_port_flag to not use an atomic notifier, it should be called from outside spinlock context. We can temporarily drop br->lock, but that creates some concurrency complications (example below is given for sysfs): - There might be an "echo 1 > multicast_flood" simultaneous with an "echo 0 > multicast_flood". The result of this is nondeterministic either way, so I'm not too concerned as long as the result is consistent (no other flags have changed). - There might be an "echo 1 > multicast_flood" simultaneous with an "echo 0 > learning". My expectation is that none of the two writes are "eaten", and the final flags contain BR_MCAST_FLOOD=1 and BR_LEARNING=0 regardless of the order of execution. That is actually possible if, on the commit path, we don't do a trivial "p->flags = flags" which might overwrite bits outside of our mask, but instead we just change the flags corresponding to our mask. Now that br_switchdev_set_port_flag is never called from under br->lock, it runs in sleepable context. All switchdev drivers handle SWITCHDEV_PORT_ATTR_SET as both blocking and atomic, so no changes are needed on that front. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- Changes in v3: - Drop the br->lock around br_switchdev_set_port_flag in this patch, for both sysfs and netlink. - Only set/restore the masked bits in p->flags to avoid concurrency issues. Changes in v2: Patch is new. net/bridge/br_netlink.c | 10 +++++++--- net/bridge/br_switchdev.c | 5 ++--- net/bridge/br_sysfs_if.c | 22 ++++++++++++++-------- 3 files changed, 23 insertions(+), 14 deletions(-) diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index b7731614c036..8f09106966c4 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -869,7 +869,7 @@ static void br_set_port_flag(struct net_bridge_port *p, struct nlattr *tb[], static int br_setport(struct net_bridge_port *p, struct nlattr *tb[], struct netlink_ext_ack *extack) { - unsigned long old_flags, changed_mask; + unsigned long flags, old_flags, changed_mask; bool br_vlan_tunnel_old; int err; @@ -896,10 +896,14 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[], br_set_port_flag(p, tb, IFLA_BRPORT_ISOLATED, BR_ISOLATED); changed_mask = old_flags ^ p->flags; + flags = p->flags; - err = br_switchdev_set_port_flag(p, p->flags, changed_mask, extack); + spin_unlock_bh(&p->br->lock); + err = br_switchdev_set_port_flag(p, flags, changed_mask, extack); + spin_lock_bh(&p->br->lock); if (err) { - p->flags = old_flags; + p->flags &= ~changed_mask; + p->flags |= (old_flags & changed_mask); goto out; } diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c index dbd94156960f..a79164ee65b9 100644 --- a/net/bridge/br_switchdev.c +++ b/net/bridge/br_switchdev.c @@ -79,9 +79,8 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p, attr.u.brport_flags.val = flags & mask; attr.u.brport_flags.mask = mask; - /* We run from atomic context here */ - err = call_switchdev_notifiers(SWITCHDEV_PORT_ATTR_SET, p->dev, - &info.info, extack); + err = call_switchdev_blocking_notifiers(SWITCHDEV_PORT_ATTR_SET, p->dev, + &info.info, extack); err = notifier_to_errno(err); if (err == -EOPNOTSUPP) return 0; diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c index 72e92376eef1..3f21fdd1cdaa 100644 --- a/net/bridge/br_sysfs_if.c +++ b/net/bridge/br_sysfs_if.c @@ -68,16 +68,22 @@ static int store_flag(struct net_bridge_port *p, unsigned long v, else flags &= ~mask; - if (flags != p->flags) { - err = br_switchdev_set_port_flag(p, flags, mask, &extack); - if (err) { - netdev_err(p->dev, "%s\n", extack._msg); - return err; - } + if (flags == p->flags) + return 0; - p->flags = flags; - br_port_flags_change(p, mask); + spin_unlock_bh(&p->br->lock); + err = br_switchdev_set_port_flag(p, flags, mask, &extack); + spin_lock_bh(&p->br->lock); + if (err) { + netdev_err(p->dev, "%s\n", extack._msg); + return err; } + + p->flags &= ~mask; + p->flags |= (flags & mask); + + br_port_flags_change(p, mask); + return 0; } -- 2.25.1
next prev parent reply other threads:[~2021-02-10 9:27 UTC|newest] Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-02-10 9:14 [PATCH v3 net-next 00/11] Cleanup in brport flags switchdev offload for DSA Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 9:14 ` [PATCH v3 net-next 01/11] net: switchdev: propagate extack to port attributes Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-11 4:12 ` Florian Fainelli 2021-02-11 4:12 ` [Bridge] " Florian Fainelli 2021-02-10 9:14 ` [PATCH v3 net-next 02/11] net: bridge: offload all port flags at once in br_setport Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 9:14 ` [PATCH v3 net-next 03/11] net: bridge: don't print in br_switchdev_set_port_flag Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 9:14 ` [PATCH v3 net-next 04/11] net: dsa: configure proper brport flags when ports leave the bridge Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-11 4:16 ` Florian Fainelli 2021-02-11 4:16 ` [Bridge] " Florian Fainelli 2021-02-10 9:14 ` [PATCH v3 net-next 05/11] net: squash switchdev attributes PRE_BRIDGE_FLAGS and BRIDGE_FLAGS Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 9:14 ` [PATCH v3 net-next 06/11] net: dsa: kill .port_egress_floods overengineering Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-11 4:18 ` Florian Fainelli 2021-02-11 4:18 ` [Bridge] " Florian Fainelli 2021-02-10 9:14 ` [PATCH v3 net-next 07/11] net: prep switchdev drivers for concurrent SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 10:12 ` Ido Schimmel 2021-02-10 10:12 ` [Bridge] " Ido Schimmel 2021-02-10 10:23 ` Vladimir Oltean 2021-02-10 10:23 ` [Bridge] " Vladimir Oltean 2021-02-10 23:34 ` David Miller 2021-02-10 23:34 ` [Bridge] " David Miller 2021-02-10 9:14 ` Vladimir Oltean [this message] 2021-02-10 9:14 ` [Bridge] [PATCH v3 net-next 08/11] net: bridge: put SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS on the blocking call chain Vladimir Oltean 2021-02-10 10:14 ` Nikolay Aleksandrov 2021-02-10 10:14 ` [Bridge] " Nikolay Aleksandrov 2021-02-10 9:14 ` [PATCH v3 net-next 09/11] net: mscc: ocelot: use separate flooding PGID for broadcast Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-11 4:19 ` Florian Fainelli 2021-02-11 4:19 ` [Bridge] " Florian Fainelli 2021-02-10 9:14 ` [PATCH v3 net-next 10/11] net: mscc: ocelot: offload bridge port flags to device Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-11 4:20 ` Florian Fainelli 2021-02-11 4:20 ` [Bridge] " Florian Fainelli 2021-02-10 9:14 ` [PATCH v3 net-next 11/11] net: dsa: sja1105: " Vladimir Oltean 2021-02-10 9:14 ` [Bridge] " Vladimir Oltean 2021-02-10 10:31 ` [PATCH v3 net-next 00/11] Cleanup in brport flags switchdev offload for DSA Nikolay Aleksandrov 2021-02-10 10:31 ` [Bridge] " Nikolay Aleksandrov 2021-02-10 10:45 ` Vladimir Oltean 2021-02-10 10:45 ` [Bridge] " Vladimir Oltean 2021-02-10 10:52 ` Nikolay Aleksandrov 2021-02-10 10:52 ` [Bridge] " Nikolay Aleksandrov 2021-02-10 11:01 ` Vladimir Oltean 2021-02-10 11:01 ` [Bridge] " Vladimir Oltean 2021-02-10 11:05 ` Nikolay Aleksandrov 2021-02-10 11:05 ` [Bridge] " Nikolay Aleksandrov 2021-02-10 12:01 ` Vladimir Oltean 2021-02-10 12:01 ` [Bridge] " Vladimir Oltean 2021-02-10 12:10 ` Nikolay Aleksandrov 2021-02-10 12:10 ` [Bridge] " Nikolay Aleksandrov 2021-02-10 12:21 ` Ido Schimmel 2021-02-10 12:21 ` [Bridge] " Ido Schimmel 2021-02-10 12:29 ` Vladimir Oltean 2021-02-10 12:29 ` [Bridge] " Vladimir Oltean 2021-02-10 12:38 ` Ido Schimmel 2021-02-10 12:38 ` [Bridge] " Ido Schimmel 2021-02-10 12:55 ` Vladimir Oltean 2021-02-10 12:55 ` [Bridge] " Vladimir Oltean 2021-02-10 12:59 ` Ido Schimmel 2021-02-10 12:59 ` [Bridge] " Ido Schimmel
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