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Message-Id: <1440782540-7876-1-git-send-email-razor@blackwall.org>
Date: Fri, 28 Aug 2015 10:22:20 -0700
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: netdev@...r.kernel.org
Cc: 13806511171@....com, shemminger@...ux-foundation.org,
maheshb@...gle.com, j.vosburgh@...il.com, vfalico@...il.com,
gospo@...ulusnetworks.com, davem@...emloft.net,
Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: [PATCH net v2] bonding: fix bond_poll_controller bh_enable warning
From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
The problem is rcu_read_unlock_bh() which triggers a warning when irqs are
disabled.
ndo_poll_controller can run with bh enabled, disabled or irqs disabled
so check if that is the case and acquire rcu_read_lock_bh only when not
running with disabled irqs. The only potential problem is with
netpoll_send_udp() currently because it can call find_skb() which may
invoke ndo_poll_controller.
We're okay w.r.t to rcu_bh when irqs are disabled so no need to acquire it.
Use the standard rcu_read_lock/unlock to make the non-bh rcu_dereference
happy.
To clarify currently the only user of netpoll_send_udp() is netconsole and
calls it with irqs disabled so we're fine.
[ 98.502922] bond0: making interface eth1 the new active one
[ 98.503039] ------------[ cut here ]------------
[ 98.503039] WARNING: CPU: 0 PID: 1744 at kernel/softirq.c:150 __local_bh_enable_ip+0x96/0xc0()
[ 98.503039] Modules linked in: bonding(OE) rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache netconsole ppdev joydev parport_pc serio_raw parport i2c_piix4 video acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd grace sunrpc virtio_net e1000 ata_generic pcnet32 mii virtio_pci virtio_ring virtio pata_acpi
[ 98.503039] CPU: 0 PID: 1744 Comm: ifenslave Tainted: G OE 4.2.0-rc7+ #56
[ 98.503039] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 98.503039] 0000000000000000 00000000e96ba230 ffff880020c236b8 ffffffff8183f105
[ 98.503039] 0000000000000000 0000000000000000 ffff880020c236f8 ffffffff810a9496
[ 98.503039] ffff88002ea99e08 0000000000000200 ffffffffa02a8e06 ffff88002ea99e08
[ 98.503039] Call Trace:
[ 98.503039] [<ffffffff8183f105>] dump_stack+0x4c/0x65
[ 98.503039] [<ffffffff810a9496>] warn_slowpath_common+0x86/0xc0
[ 98.503039] [<ffffffffa02a8e06>] ? bond_poll_controller+0x146/0x250 [bonding]
[ 98.503039] [<ffffffff810a95ca>] warn_slowpath_null+0x1a/0x20
[ 98.503039] [<ffffffff810ae376>] __local_bh_enable_ip+0x96/0xc0
[ 98.503039] [<ffffffffa02a8e2f>] bond_poll_controller+0x16f/0x250 [bonding]
[ 98.503039] [<ffffffffa02a8cf3>] ? bond_poll_controller+0x33/0x250 [bonding]
[ 98.503039] [<ffffffff810feaed>] ? trace_hardirqs_off+0xd/0x10
[ 98.503039] [<ffffffff81848afb>] ? _raw_spin_unlock_irqrestore+0x5b/0x60
[ 98.503039] [<ffffffff816ec48e>] netpoll_poll_dev+0x6e/0x350
[ 98.503039] [<ffffffff816eb977>] ? netpoll_start_xmit+0x137/0x1d0
[ 98.503039] [<ffffffff816b2e8b>] ? __alloc_skb+0x5b/0x210
[ 98.503039] [<ffffffff816ec89d>] netpoll_send_skb_on_dev+0x12d/0x2a0
[ 98.503039] [<ffffffff816eccde>] netpoll_send_udp+0x2ce/0x430
[ 98.503039] [<ffffffffa0190850>] write_msg+0xb0/0xf0 [netconsole]
[ 98.503039] [<ffffffff81116b63>] call_console_drivers.constprop.25+0x133/0x260
[ 98.503039] [<ffffffff81117934>] console_unlock+0x2f4/0x580
[ 98.503039] [<ffffffff81117ea5>] ? vprintk_emit+0x2e5/0x630
[ 98.503039] [<ffffffff81117ee5>] vprintk_emit+0x325/0x630
[ 98.503039] [<ffffffff81118379>] vprintk_default+0x29/0x40
[ 98.503039] [<ffffffff8183de4f>] printk+0x55/0x6b
[ 98.503039] [<ffffffff816c754c>] __netdev_printk+0x16c/0x260
[ 98.503039] [<ffffffff816c7a12>] netdev_info+0x62/0x80
[ 98.503039] [<ffffffffa02ab464>] bond_change_active_slave+0x134/0x6a0 [bonding]
[ 98.503039] [<ffffffffa02aba95>] bond_select_active_slave+0xc5/0x310 [bonding]
[ 98.503039] [<ffffffffa02aeb78>] bond_enslave+0x1088/0x10c0 [bonding]
[ 98.503039] [<ffffffffa02af46b>] bond_do_ioctl+0x37b/0x400 [bonding]
[ 98.503039] [<ffffffff81101d8d>] ? trace_hardirqs_on+0xd/0x10
[ 98.503039] [<ffffffff816dc437>] ? rtnl_lock+0x17/0x20
[ 98.503039] [<ffffffff816e5fd1>] dev_ifsioc+0x331/0x3e0
[ 98.503039] [<ffffffff816e62dc>] dev_ioctl+0xec/0x6c0
[ 98.503039] [<ffffffff816a6c6a>] sock_do_ioctl+0x4a/0x60
[ 98.503039] [<ffffffff816a7300>] sock_ioctl+0x1c0/0x250
[ 98.503039] [<ffffffff81271bfe>] do_vfs_ioctl+0x2ee/0x540
[ 98.503039] [<ffffffff810fd943>] ? up_read+0x23/0x40
[ 98.503039] [<ffffffff81070993>] ? __do_page_fault+0x1d3/0x420
[ 98.503039] [<ffffffff8127e246>] ? __fget_light+0x66/0x90
[ 98.503039] [<ffffffff81271ec9>] SyS_ioctl+0x79/0x90
[ 98.503039] [<ffffffff8184936e>] entry_SYSCALL_64_fastpath+0x12/0x76
[ 98.503039] ---[ end trace 00cfa804b0670051 ]---
Fixes: 616f45416ca0 ("bonding: implement bond_poll_controller()")
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
v2: make sure we're either running with irqs disabled or have rcu_bh
Making it this way to protect against future potential users of
netpoll_send_udp() which may not disable interrupts, if we agree that
it can't be called without disabling interrupts then I can resubmit this
patch without the conditional rcu_bh and possibly add a warn to catch any
future offenders that use it without disabling interrupts.
drivers/net/bonding/bond_main.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a98dd4f1b0e3..3197a2180978 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -974,12 +974,17 @@ static void bond_poll_controller(struct net_device *bond_dev)
struct ad_info ad_info;
struct netpoll_info *ni;
const struct net_device_ops *ops;
+ bool rcubh_taken = false;
if (BOND_MODE(bond) == BOND_MODE_8023AD)
if (bond_3ad_get_active_agg_info(bond, &ad_info))
return;
- rcu_read_lock_bh();
+ if (!in_irq() && !irqs_disabled()) {
+ rcu_read_lock_bh();
+ rcubh_taken = true;
+ }
+ rcu_read_lock();
bond_for_each_slave_rcu(bond, slave, iter) {
ops = slave->dev->netdev_ops;
if (!bond_slave_is_up(slave) || !ops->ndo_poll_controller)
@@ -1000,7 +1005,9 @@ static void bond_poll_controller(struct net_device *bond_dev)
ops->ndo_poll_controller(slave->dev);
up(&ni->dev_lock);
}
- rcu_read_unlock_bh();
+ rcu_read_unlock();
+ if (rcubh_taken)
+ rcu_read_unlock_bh();
}
static void bond_netpoll_cleanup(struct net_device *bond_dev)
--
2.4.3
--
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