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Florian Fainelli 7095c97345 net: systemport: Fix 64-bit stats deadlock
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: 10377ba767 ("net: systemport: Support 64bit statistics")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-15 14:24:10 -07:00
arch Merge branch 'akpm' (patches from Andrew) 2017-09-09 10:30:07 -07:00
block Merge branch 'for-4.14/block-postmerge' of git://git.kernel.dk/linux-block 2017-09-09 12:49:01 -07:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: af_alg - get_page upon reassignment to TX SGL 2017-08-22 15:03:27 +08:00
Documentation Merge branch 'for-4.14/block-postmerge' of git://git.kernel.dk/linux-block 2017-09-09 12:49:01 -07:00
drivers net: systemport: Fix 64-bit stats deadlock 2017-09-15 14:24:10 -07:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs More RDMA work and some op-structure constification from Chuck Lever, 2017-09-09 13:31:49 -07:00
include sctp: potential read out of bounds in sctp_ulpevent_type_enabled() 2017-09-13 16:59:47 -07:00
init init/main.c: extract early boot entropy from the passed cmdline 2017-09-08 18:26:50 -07:00
ipc ipc: optimize semget/shmget/msgget for lots of keys 2017-09-08 18:26:51 -07:00
kernel perf/bpf: fix a clang compilation issue 2017-09-11 14:28:45 -07:00
lib cpumask: make cpumask_next() out-of-line 2017-09-08 18:26:51 -07:00
mm mem/memcg: cache rightmost node 2017-09-08 18:26:49 -07:00
net tls: make tls_sw_free_resources static 2017-09-14 09:55:21 -07:00
samples media updates for v4.14-rc1 2017-09-07 12:53:14 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2017-09-09 10:30:07 -07:00
security audit/stable-4.14 PR 20170907 2017-09-07 20:48:25 -07:00
sound linux/kernel.h: move DIV_ROUND_DOWN_ULL() macro 2017-09-08 18:26:47 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-09 11:05:20 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
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COPYING
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