tree 7909f1fdcc05475f9575ff450356086a2c949c32
parent b5997f740b21ebb197e10a0f2fe9dc13163e1772
author Christopher Faulet <cfaulet@haproxy.com> 1507794549 +0200
committer Willy Tarreau <w@1wt.eu> 1509454712 +0100
encoding latin1

MEDIUM: threads/freq_ctr: Make the frequency counters thread-safe

When a frequency counter must be updated, we use the curr_sec/curr_tick fields
as a lock, by setting the MSB to 1 in a compare-and-swap to lock and by reseting
it to unlock. And when we need to read it, we loop until the counter is
unlocked. This way, the frequency counters are thread-safe without any external
lock. It is important to avoid increasing the size of many structures (global,
proxy, server, stick_table).