Le dimanche 06 mars 2011 Ã 08:45 +0900, Simon Horman a Ãcrit :
> From: Julian Anastasov <ja@xxxxxx>
>
> Zero the new percpu stats because we copy from there.
>
> Signed-off-by: Julian Anastasov <ja@xxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
> ---
> net/netfilter/ipvs/ip_vs_ctl.c | 17 +++++++++++++++++
> 1 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index a2a67ad..fd74527 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -715,8 +715,25 @@ static void ip_vs_trash_cleanup(struct net *net)
> static void
> ip_vs_zero_stats(struct ip_vs_stats *stats)
> {
> + struct ip_vs_cpu_stats *cpustats = stats->cpustats;
> + int i;
> +
> spin_lock_bh(&stats->lock);
>
> + for_each_possible_cpu(i) {
> + struct ip_vs_cpu_stats *u = per_cpu_ptr(cpustats, i);
> + unsigned int start;
> +
> + /* Do not pretend to be writer, it is enough to
> + * sync with writers that modify the u64 counters
> + * because under stats->lock we are the only reader.
> + */
> + do {
> + start = u64_stats_fetch_begin(&u->syncp);
> + memset(&u->ustats, 0, sizeof(u->ustats));
> + } while (u64_stats_fetch_retry(&u->syncp, start));
Sorry this makes no sense to me.
This code _is_ a writer, and hardly a hot path.
Why try to pretend its a reader and confuse people ?
Either :
- Another writer can modify the counters in same time, and we must
synchronize with them (we are a writer after all)
- Another reader can read the counters in same time, and we must let
them catch we mihjt have cleared half of their values.
- No reader or writer can access data, no synch is needed, a pure
memset() is OK.
> + }
> +
> memset(&stats->ustats, 0, sizeof(stats->ustats));
> ip_vs_zero_estimator(stats);
>
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