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Revert "Fix for a race condition in URLSession (#949)" #1188

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Merged
merged 1 commit into from
Sep 7, 2017
Merged

Revert "Fix for a race condition in URLSession (#949)" #1188

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56 changes: 19 additions & 37 deletions Foundation/URLSession/http/MultiHandle.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -39,11 +39,7 @@ extension URLSession {
let group = DispatchGroup()
fileprivate var easyHandles: [_EasyHandle] = []
fileprivate var timeoutSource: _TimeoutSource? = nil

//SR-4567: we need to synchronize the register/unregister commands to the epoll machinery in libdispatch
fileprivate let commandQueue: DispatchQueue = DispatchQueue(label: "Register-unregister synchronization")
fileprivate var cancelInProgress: DispatchSemaphore? = nil


init(configuration: URLSession._Configuration, workQueue: DispatchQueue) {
queue = DispatchQueue(label: "MultiHandle.isolation", target: workQueue)
setupCallbacks()
Expand Down Expand Up @@ -103,33 +99,25 @@ fileprivate extension URLSession._MultiHandle {
// through libdispatch (DispatchSource) and store the source(s) inside
// a `SocketSources` which we in turn store inside libcurl's multi handle
// by means of curl_multi_assign() -- we retain the object fist.
commandQueue.async {
self.cancelInProgress?.wait()
self.cancelInProgress = nil

let action = _SocketRegisterAction(rawValue: CFURLSessionPoll(value: what))
var socketSources = _SocketSources.from(socketSourcePtr: socketSourcePtr)
if socketSources == nil && action.needsSource {
let s = _SocketSources()
let p = Unmanaged.passRetained(s).toOpaque()
CFURLSessionMultiHandleAssign(self.rawHandle, socket, UnsafeMutableRawPointer(p))
socketSources = s
} else if socketSources != nil && action == .unregister {
//the beginning of an unregister operation
self.cancelInProgress = DispatchSemaphore(value: 0)
// We need to release the stored pointer:
if let opaque = socketSourcePtr {
Unmanaged<_SocketSources>.fromOpaque(opaque).release()
}
socketSources?.tearDown(self.cancelInProgress)
socketSources = nil
let action = _SocketRegisterAction(rawValue: CFURLSessionPoll(value: what))
var socketSources = _SocketSources.from(socketSourcePtr: socketSourcePtr)
if socketSources == nil && action.needsSource {
let s = _SocketSources()
let p = Unmanaged.passRetained(s).toOpaque()
CFURLSessionMultiHandleAssign(rawHandle, socket, UnsafeMutableRawPointer(p))
socketSources = s
} else if socketSources != nil && action == .unregister {
// We need to release the stored pointer:
if let opaque = socketSourcePtr {
Unmanaged<_SocketSources>.fromOpaque(opaque).release()
}
if let ss = socketSources {
let handler = DispatchWorkItem { [weak self] in
self?.performAction(for: socket)
}
ss.createSources(with: action, fileDescriptor: Int(socket), queue: self.queue, handler: handler)
socketSources = nil
}
if let ss = socketSources {
let handler = DispatchWorkItem { [weak self] in
self?.performAction(for: socket)
}
ss.createSources(with: action, fileDescriptor: Int(socket), queue: queue, handler: handler)
}
return 0
}
Expand Down Expand Up @@ -411,18 +399,12 @@ fileprivate class _SocketSources {
s.resume()
}

func tearDown(_ cancelInProgress: DispatchSemaphore?) {
let cancelHandler = DispatchWorkItem {
//the real end of an unregister operation!
cancelInProgress?.signal()
}
func tearDown() {
if let s = readSource {
s.setCancelHandler(handler: cancelHandler)
s.cancel()
}
readSource = nil
if let s = writeSource {
s.setCancelHandler(handler: cancelHandler)
s.cancel()
}
writeSource = nil
Expand Down