From abf01a0eb724aa82a5b2465c1dbde67bcc795727 Mon Sep 17 00:00:00 2001
From: "M@" <m@cognusion.com>
Date: Thu, 25 Apr 2024 18:46:12 -0400
Subject: [PATCH] Fixes unlocked read from logBuffer.LastTsNs that is racey.
 (#5536)

---
 weed/util/log_buffer/log_read.go | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/weed/util/log_buffer/log_read.go b/weed/util/log_buffer/log_read.go
index c3dd0f288..0d044fc14 100644
--- a/weed/util/log_buffer/log_read.go
+++ b/weed/util/log_buffer/log_read.go
@@ -66,9 +66,17 @@ func (logBuffer *LogBuffer) LoopProcessLogData(readerName string, startPosition
 				isDone = true
 				return
 			}
+			logBuffer.RLock()
 			lastTsNs := logBuffer.LastTsNs
-			for lastTsNs == logBuffer.LastTsNs {
+			logBuffer.RUnlock()
+			loopTsNs := lastTsNs // make a copy
+
+			for lastTsNs == loopTsNs {
 				if waitForDataFn() {
+					// Update loopTsNs and loop again
+					logBuffer.RLock()
+					loopTsNs = logBuffer.LastTsNs
+					logBuffer.RUnlock()
 					continue
 				} else {
 					isDone = true