frostruan commented on code in PR #4859:
URL: https://github.com/apache/hbase/pull/4859#discussion_r1011250021
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hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionScannerImpl.java:
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@@ -130,19 +130,34 @@ private static boolean hasNonce(HRegion region, long
nonce) {
long mvccReadPoint = PackagePrivateFieldAccessor.getMvccReadPoint(scan);
this.scannerReadPoints = region.scannerReadPoints;
this.rsServices = region.getRegionServerServices();
- synchronized (scannerReadPoints) {
- if (mvccReadPoint > 0) {
- this.readPt = mvccReadPoint;
- } else if (hasNonce(region, nonce)) {
- this.readPt =
rsServices.getNonceManager().getMvccFromOperationContext(nonceGroup, nonce);
- } else {
- this.readPt = region.getReadPoint(isolationLevel);
+ if (region.useReadWriteLockForReadPoints) {
+ region.scannerReadPointsLock.readLock().lock();
+ try {
+ this.readPt = calculateReadPoint(isolationLevel, mvccReadPoint,
nonceGroup, nonce);
+ scannerReadPoints.put(this, this.readPt);
Review Comment:
Thanks for the review Duo
The scannerReadPoints is ConcurrentHashMap, which is thread-safe. So we can
modified it concurrently. Shared lock is enough. But when getSmallestReadPoint,
we need to ensure that scannerReadPoints can not be modified, we need exclusive
lock.
So when modify it, we need to acquire shared lock and when read it, we need
to acquire exclusive lock.
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