Improved performance of PortScanRateLimiter by sleeping outside of synchronized block.

Potential carrier thread pinning through sleeping inside sync block is now being prevented

1 files changed, 17 insertions, 4 deletions

diff --git a/src/main/java/com/it_jaros/jns/scan/engine/PortScanRateLimiter.java b/src/main/java/com/it_jaros/jns/scan/engine/PortScanRateLimiter.java
index aa897a4..3411367 100644
--- a/src/main/java/com/it_jaros/jns/scan/engine/PortScanRateLimiter.java
+++ b/src/main/java/com/it_jaros/jns/scan/engine/PortScanRateLimiter.java
@@ -23,16 +23,29 @@ public class PortScanRateLimiter {
         if (delayInNanos <= 0) {
             return;
         }
+
+        long deadlineNanos;
         synchronized (lock) {
             if (cancelledToken.isCancelled()) {
                 return;
             }
             long now = System.nanoTime();
-            if (nextAllowedTime > now) {
-                LockSupport.parkNanos(nextAllowedTime - now);
-                now = System.nanoTime();  // re-read after waking
+            if (nextAllowedTime <= now) {
+                // a slot is free: claim it and proceed immediately
+                nextAllowedTime = now + delayInNanos;
+                return;
             }
-            nextAllowedTime = now + delayInNanos;
+            // claim my slot now, wait for it later
+            deadlineNanos = nextAllowedTime;
+            nextAllowedTime += delayInNanos;
+        }
+
+        // wait outside the lock so the thread is not blocked
+        // while holding the monitor (which would pin virtual threads)
+        LockSupport.parkNanos(Math.max(0, deadlineNanos - System.nanoTime()));
+
+        if (cancelledToken.isCancelled()) {
+            return;
         }
     }
 }