netdev - Re: [PATCH net v3] bonding: fix bond_poll_controller bh

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Message-ID: <CAF2d9jiuEpRRdbW3V4Kiu0Z5N62C_5Zy08o9CHfOtTBZvMC-dg@mail.gmail.com>
Date:	Fri, 28 Aug 2015 15:32:47 -0700
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	Nikolay Aleksandrov <razor@...ckwall.org>
Cc:	linux-netdev <netdev@...r.kernel.org>, 13806511171@....com,
	shemminger@...ux-foundation.org, j.vosburgh@...il.com,
	vfalico@...il.com, gospo@...ulusnetworks.com,
	David Miller <davem@...emloft.net>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: Re: [PATCH net v3] bonding: fix bond_poll_controller bh_enable warning

On Fri, Aug 28, 2015 at 3:05 PM, Nikolay Aleksandrov
<razor@...ckwall.org> wrote:
>
> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>
> The problem is rcu_read_unlock_bh() which triggers a warning when irqs are
> disabled. ndo_poll_controller should run with irqs disabled always so we
> can drop the rcu_read_lock_bh.
>
> [   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>
Acked-by: Mahesh Bandewar <maheshb@...gle.com>
> ---
> v3: After Dave made it clear that poll_controller should always be called
> with interrupts disabled we can simply drop the rcu bh lock.
>
I agree with Dave's logic and future users probably have to follow the
same logic.

>  drivers/net/bonding/bond_main.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index a98dd4f1b0e3..7ab72692d7fd 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -979,7 +979,6 @@ 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();
>         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 +999,6 @@ static void bond_poll_controller(struct net_device *bond_dev)
>                 ops->ndo_poll_controller(slave->dev);
>                 up(&ni->dev_lock);
>         }
> -       rcu_read_unlock_bh();
>  }
>
>  static void bond_netpoll_cleanup(struct net_device *bond_dev)
> --
> 2.4.3
>
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