From: Willy Tarreau <w@1wt.eu>
Date: Tue, 6 May 2025 03:11:56 +0000 (+0200)
Subject: DEBUG: threads: display held locks in threads dumps
X-Git-Tag: v3.2-dev15~28
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3bb6eea6d56d0328437ed34ac97d4479051ee2c9;p=thirdparty%2Fhaproxy.git

DEBUG: threads: display held locks in threads dumps

Based on the lock history, we can spot some locks that are still held
by checking the last operation that happened on them: if it's not an
unlock, then we know the lock is held. In this case we append the list
after "locked:" with their label and state like below:

  U:QUEUE S:IDLE_CONNS U:IDLE_CONNS R:TASK_WQ U:TASK_WQ S:QUEUE S:QUEUE S:QUEUE locked: QUEUE(S)
  S:IDLE_CONNS U:IDLE_CONNS S:TASK_RQ U:TASK_RQ S:QUEUE U:QUEUE S:IDLE_CONNS locked: IDLE_CONNS(S)
  R:TASK_WQ S:TASK_WQ R:TASK_WQ S:TASK_WQ R:TASK_WQ S:TASK_WQ R:TASK_WQ locked: TASK_WQ(R)
  W:STK_TABLE W:STK_TABLE_UPDT U:STK_TABLE_UPDT W:STK_TABLE W:STK_TABLE_UPDT U:STK_TABLE_UPDT W:STK_TABLE W:STK_TABLE_UPDT locked: STK_TABLE(W) STK_TABLE_UPDT(W)

The format is slightly different (label(status)) so as to easily
differentiate them visually from the history.
---

diff --git a/src/debug.c b/src/debug.c
index 1d6b30a7a..f92b5ff80 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -355,7 +355,8 @@ void ha_thread_dump_one(struct buffer *buf, int is_caller)
 #if defined(USE_THREAD) && ((DEBUG_THREAD > 0) || defined(DEBUG_FULL))
 	/* List the lock history */
 	if (th_ctx->lock_history) {
-		int lkh, lkl;
+		int lkh, lkl, lbl;
+		int done;
 
 		chunk_appendf(buf, "             lock_hist:");
 		for (lkl = 7; lkl >= 0; lkl--) {
@@ -365,6 +366,29 @@ void ha_thread_dump_one(struct buffer *buf, int is_caller)
 			chunk_appendf(buf, " %c:%s",
 				      "URSW"[lkh & 3], lock_label((lkh >> 2) - 1));
 		}
+
+		/* now rescan the list to only show those that remain */
+		done = 0;
+		for (lbl = 0; lbl < LOCK_LABELS; lbl++) {
+			/* find the latest occurrence of each label */
+			for (lkl = 0; lkl < 8; lkl++) {
+				lkh = (th_ctx->lock_history >> (lkl * 8)) & 0xff;
+				if (!lkh)
+					continue;
+				if ((lkh >> 2) == lbl)
+					break;
+			}
+			if (lkl == 8) // not found
+				continue;
+			if ((lkh & 3) == _LK_UN)
+				continue;
+			if (!done)
+				chunk_appendf(buf, " locked:");
+			chunk_appendf(buf, " %s(%c)",
+				      lock_label((lkh >> 2) - 1),
+				      "URSW"[lkh & 3]);
+			done++;
+		}
 		chunk_appendf(buf, "\n");
 	}
 #endif