diff options
Diffstat (limited to 'drivers/net/ethernet/sfc/nic.h')
| -rw-r--r-- | drivers/net/ethernet/sfc/nic.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/drivers/net/ethernet/sfc/nic.h b/drivers/net/ethernet/sfc/nic.h index f48ccf6bb3b..bab5cd9f574 100644 --- a/drivers/net/ethernet/sfc/nic.h +++ b/drivers/net/ethernet/sfc/nic.h @@ -294,6 +294,24 @@ extern bool falcon_xmac_check_fault(struct efx_nic *efx); extern int falcon_reconfigure_xmac(struct efx_nic *efx); extern void falcon_update_stats_xmac(struct efx_nic *efx); +/* Some statistics are computed as A - B where A and B each increase + * linearly with some hardware counter(s) and the counters are read + * asynchronously. If the counters contributing to B are always read + * after those contributing to A, the computed value may be lower than + * the true value by some variable amount, and may decrease between + * subsequent computations. + * + * We should never allow statistics to decrease or to exceed the true + * value. Since the computed value will never be greater than the + * true value, we can achieve this by only storing the computed value + * when it increases. + */ +static inline void efx_update_diff_stat(u64 *stat, u64 diff) +{ + if ((s64)(diff - *stat) > 0) + *stat = diff; +} + /* Interrupts and test events */ extern int efx_nic_init_interrupt(struct efx_nic *efx); extern void efx_nic_enable_interrupts(struct efx_nic *efx); |