WIP: atomic warning?

This approach is easy (we initialize from a few places + dnspatrol),
but this would make a section not portable to knot-dns verbatim.

diff --git a/lib/kru.inc.c b/lib/kru.inc.c
index 35dd2e2908a5a153edba0649601cb34309ff9252..04f77f5903c33c4c00939672598a3aa32a9237d0 100644 (file)
--- a/lib/kru.inc.c
+++ b/lib/kru.inc.c
@@ -233,6 +233,15 @@ static bool kru_initialize(struct kru *kru, int capacity_log, kru_price_t max_de
 
        decay_initialize(&kru->decay, max_decay);
 
+       // We use atomic_ ops on uint16_t and uint32_t, but those don't have their own macros.
+       bool ok = ATOMIC_CHAR16_T_LOCK_FREE == 2 && ATOMIC_CHAR32_T_LOCK_FREE == 2;
+       static bool warned = false;
+       if (!ok && !warned) {
+               warned = true;
+               kr_log_warning(SYSTEM, "warning: KRU might be surprisingly slow\n");
+               // practically this happens on pre-ARMv7 systems
+       }
+
        return true;
 }
 
@@ -493,7 +502,6 @@ static inline bool kru_limited_update(struct kru *kru, struct query_ctx *ctx, bo
                load_at = (_Atomic uint16_t *)ctx->load;
        }
 
-       static_assert(ATOMIC_CHAR16_T_LOCK_FREE == 2, "insufficient atomics");
        const uint16_t price = ctx->price16;
        const uint32_t limit = ctx->limit16;  // 2^16 has to be representable
        uint16_t load_orig = atomic_load_explicit(load_at, memory_order_relaxed);