We can enter a deadlock situation because there is no sufficient protection
when ndo_get_stats64() runs in process context to guard against RX or TX NAPI
contexts running in softirq, this can lead to the following lockdep splat and
actual deadlock was experienced as well with an iperf session in the background
and a while loop doing ifconfig + ethtool.
[ 5.780350] ================================
[ 5.784679] WARNING: inconsistent lock state
[ 5.789011] 4.13.0-rc7-02179-g32fae27c725d #70 Not tainted
[ 5.794561] --------------------------------
[ 5.798890] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 5.804971] swapper/0/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
[ 5.810175] (&syncp->seq#2){+.?...}, at: [<c0768a28>] bcm_sysport_tx_reclaim+0x30/0x54
[ 5.818327] {SOFTIRQ-ON-W} state was registered at:
[ 5.823278] bcm_sysport_get_stats64+0x17c/0x258
[ 5.828053] dev_get_stats+0x38/0xac
[ 5.831776] rtnl_fill_stats+0x30/0x118
[ 5.835761] rtnl_fill_ifinfo+0x538/0xe24
[ 5.839921] rtmsg_ifinfo_build_skb+0x6c/0xd8
[ 5.844430] rtmsg_ifinfo_event.part.5+0x14/0x44
[ 5.849201] rtmsg_ifinfo+0x20/0x28
[ 5.852837] register_netdevice+0x628/0x6b8
[ 5.857171] register_netdev+0x14/0x24
[ 5.861051] bcm_sysport_probe+0x30c/0x438
[ 5.865280] platform_drv_probe+0x50/0xb0
[ 5.869418] driver_probe_device+0x2e8/0x450
[ 5.873817] __driver_attach+0x104/0x120
[ 5.877871] bus_for_each_dev+0x7c/0xc0
[ 5.881834] bus_add_driver+0x1b0/0x270
[ 5.885797] driver_register+0x78/0xf4
[ 5.889675] do_one_initcall+0x54/0x190
[ 5.893646] kernel_init_freeable+0x144/0x1d0
[ 5.898135] kernel_init+0x8/0x110
[ 5.901665] ret_from_fork+0x14/0x2c
[ 5.905363] irq event stamp: 24263
[ 5.908804] hardirqs last enabled at (24262): [<c08eecf0>] net_rx_action+0xc4/0x4e4
[ 5.916624] hardirqs last disabled at (24263): [<c0a7da00>] _raw_spin_lock_irqsave+0x1c/0x98
[ 5.925143] softirqs last enabled at (24258): [<c022a7fc>] irq_enter+0x84/0x98
[ 5.932524] softirqs last disabled at (24259): [<c022a918>] irq_exit+0x108/0x16c
[ 5.939985]
[ 5.939985] other info that might help us debug this:
[ 5.946576] Possible unsafe locking scenario:
[ 5.946576]
[ 5.952556] CPU0
[ 5.955031] ----
[ 5.957506] lock(&syncp->seq#2);
[ 5.960955] <Interrupt>
[ 5.963604] lock(&syncp->seq#2);
[ 5.967227]
[ 5.967227] *** DEADLOCK ***
[ 5.967227]
[ 5.973222] 1 lock held by swapper/0/0:
[ 5.977092] #0: (&(&ring->lock)->rlock){..-...}, at: [<c0768a18>] bcm_sysport_tx_reclaim+0x20/0x54
So just remove the u64_stats_update_begin()/end() pair in ndo_get_stats64()
since it does not appear to be useful for anything. No inconsistency was
observed with either ifconfig or ethtool, global TX counts equal the sum of
per-queue TX counts on a 32-bit architecture.
Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
drivers/net/ethernet/broadcom/bcmsysport.c | 3 ---
1 file changed, 3 deletions(-)
From: Eric Dumazet <hidden> Date: 2017-09-12 21:38:15
On Tue, 2017-09-12 at 13:14 -0700, Florian Fainelli wrote:
We can enter a deadlock situation because there is no sufficient protection
when ndo_get_stats64() runs in process context to guard against RX or TX NAPI
contexts running in softirq, this can lead to the following lockdep splat and
actual deadlock was experienced as well with an iperf session in the background
and a while loop doing ifconfig + ethtool.
quoted hunk
So just remove the u64_stats_update_begin()/end() pair in ndo_get_stats64()
since it does not appear to be useful for anything. No inconsistency was
observed with either ifconfig or ethtool, global TX counts equal the sum of
per-queue TX counts on a 32-bit architecture.
Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
drivers/net/ethernet/broadcom/bcmsysport.c | 3 ---
1 file changed, 3 deletions(-)
Yes, this u64_stats_update_begin()/u64_stats_update_end() is bogus
But why do we even write on tx_bytes/tx_packets here ???
Seems very wrong anyway.
(ethtool -S does not call bcm_sysport_get_stats64() to refresh them )
On Tue, 2017-09-12 at 13:14 -0700, Florian Fainelli wrote:
quoted
We can enter a deadlock situation because there is no sufficient protection
when ndo_get_stats64() runs in process context to guard against RX or TX NAPI
contexts running in softirq, this can lead to the following lockdep splat and
actual deadlock was experienced as well with an iperf session in the background
and a while loop doing ifconfig + ethtool.
quoted
So just remove the u64_stats_update_begin()/end() pair in ndo_get_stats64()
since it does not appear to be useful for anything. No inconsistency was
observed with either ifconfig or ethtool, global TX counts equal the sum of
per-queue TX counts on a 32-bit architecture.
Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
drivers/net/ethernet/broadcom/bcmsysport.c | 3 ---
1 file changed, 3 deletions(-)
We can enter a deadlock situation because there is no sufficient protection
when ndo_get_stats64() runs in process context to guard against RX or TX NAPI
contexts running in softirq, this can lead to the following lockdep splat and
actual deadlock was experienced as well with an iperf session in the background
and a while loop doing ifconfig + ethtool.
...
So just remove the u64_stats_update_begin()/end() pair in ndo_get_stats64()
since it does not appear to be useful for anything. No inconsistency was
observed with either ifconfig or ethtool, global TX counts equal the sum of
per-queue TX counts on a 32-bit architecture.
Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
We can enter a deadlock situation because there is no sufficient
protection
quoted
when ndo_get_stats64() runs in process context to guard against RX or
TX NAPI
quoted
contexts running in softirq, this can lead to the following lockdep
splat and
quoted
actual deadlock was experienced as well with an iperf session in the
background
quoted
and a while loop doing ifconfig + ethtool.
...
quoted
So just remove the u64_stats_update_begin()/end() pair in
ndo_get_stats64()
quoted
since it does not appear to be useful for anything. No inconsistency
was
quoted
observed with either ifconfig or ethtool, global TX counts equal the
sum of
quoted
per-queue TX counts on a 32-bit architecture.
Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Applied.
FYI, there is another patch needed to ensure consistency between ethtool reported stats and netdevice stats, will submit that after some more testing. Thanks!
--
Florian
FYI, there is another patch needed to ensure consistency between
ethtool reported stats and netdevice stats, will submit that after
some more testing. Thanks!