On 09/12/2017 02:38 PM, Eric Dumazet wrote: > 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 <f.faine...@gmail.com> >> --- >> 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 ???
That's for the ethtool -S netdev stats copy (that's on me, I added that in the driver initial version), so yes, not very robust... > > Seems very wrong anyway. > > (ethtool -S does not call bcm_sysport_get_stats64() to refresh them ) Yes that might actually be the simplest way to get this fixed. > >> 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); > > -- Florian