Fixed order of operations for RWLocks by yielding for all microtasks …

…even if not first reader
MatrixAI · Apr 1, 2022 · 8d421c0 · 8d421c0
1 parent f6463f9
commit 8d421c0
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Showing 4 changed files with 10 additions and 8 deletions.
diff --git a/src/RWLockReader.ts b/src/RWLockReader.ts
@@ -29,6 +29,9 @@ class RWLockReader {
           --this._readerCount;
           throw e;
         }
+      } else {
+        // Yield for the first reader to finish locking
+        await yieldMicro();
       }
       return [
         async () => {

diff --git a/src/RWLockWriter.ts b/src/RWLockWriter.ts
@@ -57,6 +57,9 @@ class RWLockWriter {
           --this._readerCount;
           throw e;
         }
+      } else {
+        // Yield for the first reader to finish locking
+        await yieldMicro();
       }
       return [
         async () => {

diff --git a/tests/RWLockReader.test.ts b/tests/RWLockReader.test.ts
@@ -315,7 +315,7 @@ describe(RWLockReader.name, () => {
     expect(value).toBe(2);
   });
   test('order of operations', async () => {
-    // Write-preferring order
+    // Read-preferring order
     const lock = new RWLockReader();
     const order: Array<string> = [];
     const p1 = lock.withReadF(async () => {
@@ -342,13 +342,11 @@ describe(RWLockReader.name, () => {
     await p4;
     await p5;
     await p6;
-    // Notice that `read2` happens first
-    // This can chnage if `read2` takes longer to do
     expect(order).toStrictEqual([
+      'read1',
       'read2',
       'read3',
       'read4',
-      'read1',
       'write1',
       'write2',
     ]);

diff --git a/tests/RWLockWriter.test.ts b/tests/RWLockWriter.test.ts
@@ -342,14 +342,12 @@ describe(RWLockWriter.name, () => {
     await p4;
     await p5;
     await p6;
-    // Notice that `read2` happens first
-    // This can chnage if `read2` takes longer to do
     expect(order).toStrictEqual([
-      'read2',
       'read1',
+      'read2',
       'write1',
-      'read4',
       'read3',
+      'read4',
       'write2',
     ]);
   });