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Message-Id: <658DEBCA-6BE2-4388-AFE8-58C6A71029AC@cumulusnetworks.com>
Date: Fri, 28 Aug 2015 08:33:35 -0700
From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: netdev@...r.kernel.org, 13806511171@....com,
shemminger@...ux-foundation.org, maheshb@...gle.com,
j.vosburgh@...il.com, vfalico@...il.com, gospo@...ulusnetworks.com,
davem@...emloft.net
Subject: Re: [PATCH net] bonding: fix bond_poll_controller bh_enable warning
> On Aug 27, 2015, at 6:54 PM, Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>
> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>
> The problem is rcu_read_unlock_bh() which triggers a warning.
> ndo_poll_controller is supposed to be running with either irqs disabled
> or bh disabled already, so we don't need to take rcu_read_lock_bh.
> Use the standard rcu_read_lock/unlock to make the non-bh rcu_dereference
> happy.
>
Actually I was wrong here, e.g. netpoll_send_udp(). It is currently only used by netconsole
with irqs disabled but that doesn’t have to be true for future users.
I wanted to avoid conditional lock acquiring but we may have to go that way.
I’ll post a v2 in a few hours.
Please drop this patch.
Thanks,
Nik
> This patch fixes https://bugzilla.kernel.org/show_bug.cgi?id=102181
>
> [ 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>
> ---
> drivers/net/bonding/bond_main.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index a98dd4f1b0e3..1b4b24218807 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -979,7 +979,7 @@ static void bond_poll_controller(struct net_device *bond_dev)
> if (bond_3ad_get_active_agg_info(bond, &ad_info))
> return;
>
> - rcu_read_lock_bh();
> + 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 +1000,7 @@ 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();
> }
>
> static void bond_netpoll_cleanup(struct net_device *bond_dev)
> --
> 2.4.3
>
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