tree 1721b297633a798beb166a4c8778edb1a8a474ad
parent 6afff0caa721211e8c04bdc7627ee3bff95bcb95
author Eric Dumazet <eric.dumazet@gmail.com> 1277227337 -0700
committer David S. Miller <davem@davemloft.net> 1277323187 -0700

net: Introduce u64_stats_sync infrastructure

To properly implement 64bits network statistics on 32bit or 64bit hosts,
we provide one new type and four methods, to ease conversions.

Stats producer should use following template granted it already got an
exclusive access to counters (include/linux/u64_stats_sync.h contains
some documentation about details)

    u64_stats_update_begin(&stats->syncp);
    stats->bytes64 += len;
    stats->packets64++;
    u64_stats_update_end(&stats->syncp);

While a consumer should use following template to get consistent
snapshot :

    u64 tbytes, tpackets;
    unsigned int start;

    do {
        start = u64_stats_fetch_begin(&stats->syncp);
        tbytes = stats->bytes64;
        tpackets = stats->packets64;
    } while (u64_stats_fetch_retry(&stats->lock, syncp));

Suggested by David Miller, and comments courtesy of Nick Piggin.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>