NSCondition fixes: Ensure correct use of lock()/action/unlock() sequence (#1613)

Author: spevans

Foundation/NSData.swift

@@ -210,16 +210,27 @@ open class NSData : NSObject, NSCopying, NSMutableCopying, NSSecureCoding {
         } else {
             let session = URLSession(configuration: URLSessionConfiguration.default)
             let cond = NSCondition()
+            cond.lock()
+
             var resError: Error?
             var resData: Data?
+            var taskFinished = false
             let task = session.dataTask(with: url, completionHandler: { data, response, error in
+                cond.lock()
                 resData = data
                 urlResponse = response
                 resError = error
-                cond.broadcast()
+                taskFinished = true
+                cond.signal()
+                cond.unlock()
             })
+
             task.resume()
-            cond.wait()
+            while taskFinished == false {
+                cond.wait()
+            }
+            cond.unlock()
+
             guard let data = resData else {
                 throw resError!
             }

Foundation/Process.swift

@@ -484,8 +484,8 @@ open class Process: NSObject {
 
         self.processIdentifier = pid
 
-        self.processLaunchedCondition.unlock()
         self.processLaunchedCondition.broadcast()
+        self.processLaunchedCondition.unlock()
     }
 
     open func interrupt() { NSUnimplemented() } // Not always possible. Sends SIGINT.

TestFoundation/TestNSLock.swift

@@ -76,15 +76,15 @@ class TestNSLock: XCTestCase {
 
         for t in 0..<threadCount {
             let thread = Thread() {
+                condition.lock()
                 arrayLock.lock()
                 threadsStarted[t] = true
                 arrayLock.unlock()
 
-                condition.lock()
                 condition.wait()
                 condition.unlock()
                 for _ in 1...50 {
-                    let r = (endSeconds * drand48()) / 50
+                    let r = Double.random(in: 0...0.02)
                     Thread.sleep(forTimeInterval: r)
                     if lock.lock(before: endTime) {
                         lock.unlock()

TestFoundation/TestThread.swift

@@ -54,7 +54,7 @@ class TestThread : XCTestCase {
         }
         thread.start()
 
-        let ok = condition.wait(until: Date(timeIntervalSinceNow: 10))
+        let ok = condition.wait(until: Date(timeIntervalSinceNow: 2))
         condition.unlock()
         XCTAssertTrue(ok, "NSCondition wait timed out")
     }