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net: add atomic_long_t to net_device_stats fields

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[ Upstream commit 6c1c5097781f563b70a81683ea6fdac21637573b ]

Long standing KCSAN issues are caused by data-race around
some dev->stats changes.

Most performance critical paths already use per-cpu
variables, or per-queue ones.

It is reasonable (and more correct) to use atomic operations
for the slow paths.

This patch adds an union for each field of net_device_stats,
so that we can convert paths that are not yet protected
by a spinlock or a mutex.

netdev_stats_to_stats64() no longer has an #if BITS_PER_LONG==64

Note that the memcpy() we were using on 64bit arches
had no provision to avoid load-tearing,
while atomic_long_read() is providing the needed protection
at no cost.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2022-11-15 08:53:55 +00:00
committed by Greg Kroah-Hartman
parent e2d60023af
commit 037db10e3f
3 changed files with 40 additions and 37 deletions
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58
include/linux/netdevice.h
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@@ -166,31 +166,38 @@ static inline bool dev_xmit_complete(int rc)
* (unsigned long) so they can be read and written atomically.
*/
#define NET_DEV_STAT(FIELD) \
union { \
unsigned long FIELD; \
atomic_long_t __##FIELD; \
}
struct net_device_stats {
unsigned long rx_packets;
unsigned long tx_packets;
unsigned long rx_bytes;
unsigned long tx_bytes;
unsigned long rx_errors;
unsigned long tx_errors;
unsigned long rx_dropped;
unsigned long tx_dropped;
unsigned long multicast;
unsigned long collisions;
unsigned long rx_length_errors;
unsigned long rx_over_errors;
unsigned long rx_crc_errors;
unsigned long rx_frame_errors;
unsigned long rx_fifo_errors;
unsigned long rx_missed_errors;
unsigned long tx_aborted_errors;
unsigned long tx_carrier_errors;
unsigned long tx_fifo_errors;
unsigned long tx_heartbeat_errors;
unsigned long tx_window_errors;
unsigned long rx_compressed;
unsigned long tx_compressed;
NET_DEV_STAT(rx_packets);
NET_DEV_STAT(tx_packets);
NET_DEV_STAT(rx_bytes);
NET_DEV_STAT(tx_bytes);
NET_DEV_STAT(rx_errors);
NET_DEV_STAT(tx_errors);
NET_DEV_STAT(rx_dropped);
NET_DEV_STAT(tx_dropped);
NET_DEV_STAT(multicast);
NET_DEV_STAT(collisions);
NET_DEV_STAT(rx_length_errors);
NET_DEV_STAT(rx_over_errors);
NET_DEV_STAT(rx_crc_errors);
NET_DEV_STAT(rx_frame_errors);
NET_DEV_STAT(rx_fifo_errors);
NET_DEV_STAT(rx_missed_errors);
NET_DEV_STAT(tx_aborted_errors);
NET_DEV_STAT(tx_carrier_errors);
NET_DEV_STAT(tx_fifo_errors);
NET_DEV_STAT(tx_heartbeat_errors);
NET_DEV_STAT(tx_window_errors);
NET_DEV_STAT(rx_compressed);
NET_DEV_STAT(tx_compressed);
};
#undef NET_DEV_STAT
#include <linux/cache.h>
@@ -5256,4 +5263,9 @@ do { \
extern struct net_device *blackhole_netdev;
/* Note: Avoid these macros in fast path, prefer per-cpu or per-queue counters. */
#define DEV_STATS_INC(DEV, FIELD) atomic_long_inc(&(DEV)->stats.__##FIELD)
#define DEV_STATS_ADD(DEV, FIELD, VAL) \
atomic_long_add((VAL), &(DEV)->stats.__##FIELD)
#endif /* _LINUX_NETDEVICE_H */