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.
> 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 <[email protected]>
> ---
> drivers/net/ethernet/broadcom/bcmsysport.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c
> b/drivers/net/ethernet/broadcom/bcmsysport.c
> index a6572b51435a..c3c53f6cd9e6 100644
> --- a/drivers/net/ethernet/broadcom/bcmsysport.c
> +++ b/drivers/net/ethernet/broadcom/bcmsysport.c
> @@ -1735,11 +1735,8 @@ static void bcm_sysport_get_stats64(struct net_device
> *dev,
> stats->tx_packets += tx_packets;
> }
>
> - /* lockless update tx_bytes and tx_packets */
> - u64_stats_update_begin(&priv->syncp);
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 )
> stats64->tx_bytes = stats->tx_bytes;
> stats64->tx_packets = stats->tx_packets;
> - u64_stats_update_end(&priv->syncp);
>
> do {
> start = u64_stats_fetch_begin_irq(&priv->syncp);
