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net: qualcomm: rmnet: don't over-count statistics

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[ Upstream commit 994c393bb6 ]

The purpose of the loop using u64_stats_fetch_*_irq() is to ensure
statistics on a given CPU are collected atomically. If one of the
statistics values gets updated within the begin/retry window, the
loop will run again.

Currently the statistics totals are updated inside that window.
This means that if the loop ever retries, the statistics for the
CPU will be counted more than once.

Fix this by taking a snapshot of a CPU's statistics inside the
protected window, and then updating the counters with the snapshot
values after exiting the loop.

(Also add a newline at the end of this file...)

Fixes: 192c4b5d48 ("net: qualcomm: rmnet: Add support for 64 bit stats")
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alex Elder 2021-06-11 13:26:00 -05:00 committed by Greg Kroah-Hartman
parent e3577776d6
commit 0e185a7b28
1 changed files with 9 additions and 9 deletions
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18
drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
View file

@ -125,24 +125,24 @@ static void rmnet_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *s)
{
struct rmnet_priv *priv = netdev_priv(dev);
struct rmnet_vnd_stats total_stats;
struct rmnet_vnd_stats total_stats = { };
struct rmnet_pcpu_stats *pcpu_ptr;
struct rmnet_vnd_stats snapshot;
unsigned int cpu, start;
memset(&total_stats, 0, sizeof(struct rmnet_vnd_stats));
for_each_possible_cpu(cpu) {
pcpu_ptr = per_cpu_ptr(priv->pcpu_stats, cpu);
do {
start = u64_stats_fetch_begin_irq(&pcpu_ptr->syncp);
total_stats.rx_pkts += pcpu_ptr->stats.rx_pkts;
total_stats.rx_bytes += pcpu_ptr->stats.rx_bytes;
total_stats.tx_pkts += pcpu_ptr->stats.tx_pkts;
total_stats.tx_bytes += pcpu_ptr->stats.tx_bytes;
snapshot = pcpu_ptr->stats; /* struct assignment */
} while (u64_stats_fetch_retry_irq(&pcpu_ptr->syncp, start));
total_stats.tx_drops += pcpu_ptr->stats.tx_drops;
total_stats.rx_pkts += snapshot.rx_pkts;
total_stats.rx_bytes += snapshot.rx_bytes;
total_stats.tx_pkts += snapshot.tx_pkts;
total_stats.tx_bytes += snapshot.tx_bytes;
total_stats.tx_drops += snapshot.tx_drops;
}
s->rx_packets = total_stats.rx_pkts;
@ -353,4 +353,4 @@ int rmnet_vnd_update_dev_mtu(struct rmnet_port *port,
}
return 0;
}
}