From 58266ff0dc0420cd99c4cb024476115a3dd9b5e7 Mon Sep 17 00:00:00 2001
From: Tom Clegg <tom@curii.com>
Date: Tue, 23 Aug 2022 11:02:04 -0400
Subject: [PATCH] 19414: Fix concurrent map read/write.

Occurred when a block was referenced by a collection but not returned
by any keepstore index, and NumCPU > 2.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>
---
 services/keep-balance/block_state.go      |  6 +++++-
 services/keep-balance/block_state_test.go | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/services/keep-balance/block_state.go b/services/keep-balance/block_state.go
index 07c9952f90..63a994096b 100644
--- a/services/keep-balance/block_state.go
+++ b/services/keep-balance/block_state.go
@@ -151,7 +151,11 @@ func (bsm *BlockStateMap) GetConfirmedReplication(blkids []arvados.SizedDigest,
 		for _, c := range classes {
 			perclass[c] = 0
 		}
-		for _, r := range bsm.get(blkid).Replicas {
+		bs, ok := bsm.entries[blkid]
+		if !ok {
+			return 0
+		}
+		for _, r := range bs.Replicas {
 			total += r.KeepMount.Replication
 			mntclasses := r.KeepMount.StorageClasses
 			if len(mntclasses) == 0 {
diff --git a/services/keep-balance/block_state_test.go b/services/keep-balance/block_state_test.go
index 8a58be288f..c6076bbd3d 100644
--- a/services/keep-balance/block_state_test.go
+++ b/services/keep-balance/block_state_test.go
@@ -5,6 +5,7 @@
 package keepbalance
 
 import (
+	"sync"
 	"time"
 
 	"git.arvados.org/arvados.git/sdk/go/arvados"
@@ -92,3 +93,25 @@ func (s *confirmedReplicationSuite) TestBlocksOnMultipleMounts(c *check.C) {
 	n = s.blockStateMap.GetConfirmedReplication([]arvados.SizedDigest{knownBlkid(40), knownBlkid(41)}, nil)
 	c.Check(n, check.Equals, 4)
 }
+
+func (s *confirmedReplicationSuite) TestConcurrency(c *check.C) {
+	var wg sync.WaitGroup
+	for i := 1000; i < 1256; i++ {
+		i := i
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			n := s.blockStateMap.GetConfirmedReplication([]arvados.SizedDigest{knownBlkid(i), knownBlkid(i)}, []string{"default"})
+			c.Check(n, check.Equals, 0)
+		}()
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			n := s.blockStateMap.GetConfirmedReplication([]arvados.SizedDigest{knownBlkid(10)}, []string{"default"})
+			c.Check(n, check.Equals, 1)
+			n = s.blockStateMap.GetConfirmedReplication([]arvados.SizedDigest{knownBlkid(20)}, []string{"default"})
+			c.Check(n, check.Equals, 2)
+		}()
+	}
+	wg.Wait()
+}
-- 
2.30.2