From 89f011ba1348b1b7ec60b73650343be34d2d525c Mon Sep 17 00:00:00 2001
From: Banana Duck <56518282+Alhanaqtah@users.noreply.github.com>
Date: Wed, 9 Jul 2025 16:37:55 +0300
Subject: [PATCH] fix: unlock of unlocked mutex (#16332)

* fix: unlock on unlocked mutex

Signed-off-by: Usama Alhanaqtah <a.usama@yandex.ru>

* test coverage

Signed-off-by: Usama Alhanaqtah <a.usama@yandex.ru>

---------

Signed-off-by: Usama Alhanaqtah <a.usama@yandex.ru>
Co-authored-by: alhanaqtah.usama <alhanaqtah.usama@DEV-254.local>
---
 tsdb/head_append.go |  9 +++++++++
 tsdb/head_test.go   | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/tsdb/head_append.go b/tsdb/head_append.go
index 03800b2455..05299f048d 100644
--- a/tsdb/head_append.go
+++ b/tsdb/head_append.go
@@ -799,13 +799,17 @@ func (a *headAppender) AppendHistogramCTZeroSample(ref storage.SeriesRef, lset l
 			if errors.Is(err, storage.ErrOutOfOrderSample) {
 				return 0, storage.ErrOutOfOrderCT
 			}
+
+			return 0, err
 		}
+
 		// OOO is not allowed because after the first scrape, CT will be the same for most (if not all) future samples.
 		// This is to prevent the injected zero from being marked as OOO forever.
 		if isOOO {
 			s.Unlock()
 			return 0, storage.ErrOutOfOrderCT
 		}
+
 		s.pendingCommit = true
 		s.Unlock()
 		a.histograms = append(a.histograms, record.RefHistogramSample{
@@ -832,13 +836,17 @@ func (a *headAppender) AppendHistogramCTZeroSample(ref storage.SeriesRef, lset l
 			if errors.Is(err, storage.ErrOutOfOrderSample) {
 				return 0, storage.ErrOutOfOrderCT
 			}
+
+			return 0, err
 		}
+
 		// OOO is not allowed because after the first scrape, CT will be the same for most (if not all) future samples.
 		// This is to prevent the injected zero from being marked as OOO forever.
 		if isOOO {
 			s.Unlock()
 			return 0, storage.ErrOutOfOrderCT
 		}
+
 		s.pendingCommit = true
 		s.Unlock()
 		a.floatHistograms = append(a.floatHistograms, record.RefFloatHistogramSample{
@@ -852,6 +860,7 @@ func (a *headAppender) AppendHistogramCTZeroSample(ref storage.SeriesRef, lset l
 	if ct > a.maxt {
 		a.maxt = ct
 	}
+
 	return storage.SeriesRef(s.ref), nil
 }
 
diff --git a/tsdb/head_test.go b/tsdb/head_test.go
index 485b8b7b1f..fd3690e065 100644
--- a/tsdb/head_test.go
+++ b/tsdb/head_test.go
@@ -6717,6 +6717,50 @@ func TestHeadAppender_AppendCT(t *testing.T) {
 	}
 }
 
+func TestHeadAppender_AppendHistogramCTZeroSample(t *testing.T) {
+	testHistogram := tsdbutil.GenerateTestHistogram(1)
+	type appendableSamples struct {
+		ts int64
+		h  *histogram.Histogram
+		fh *histogram.FloatHistogram
+		ct int64
+	}
+	for _, tc := range []struct {
+		name              string
+		appendableSamples []appendableSamples
+		expectedError     error
+	}{
+		{
+			name: "CT lower than minValidTime initiates ErrOutOfBounds",
+			appendableSamples: []appendableSamples{
+				{ts: 100, h: testHistogram, ct: -1},
+			},
+			expectedError: storage.ErrOutOfBounds,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			h, _ := newTestHead(t, DefaultBlockDuration, compression.None, false)
+
+			defer func() {
+				require.NoError(t, h.Close())
+			}()
+
+			a := h.Appender(context.Background())
+			lbls := labels.FromStrings("foo", "bar")
+
+			for _, sample := range tc.appendableSamples {
+				ref, err := a.AppendHistogramCTZeroSample(0, lbls, sample.ts, sample.ct, sample.h, sample.fh)
+				require.ErrorIs(t, err, tc.expectedError)
+
+				_, err = a.AppendHistogram(ref, lbls, sample.ts, sample.h, sample.fh)
+				require.NoError(t, err)
+			}
+
+			require.NoError(t, a.Commit())
+		})
+	}
+}
+
 func TestHeadCompactableDoesNotCompactEmptyHead(t *testing.T) {
 	// Use a chunk range of 1 here so that if we attempted to determine if the head
 	// was compactable using default values for min and max times, `Head.compactable()`