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Terminating multiple operations without a deadlock
0
I have multiple background threads which update the UI from time to time. I need to terminate them properly from the UI thread and be sure that there's no deadlock/race condition.
Here's an example that creates 100 operations and then terminates them:
class CancellationToken {
private let updateLock = DispatchSemaphore(value: 1)
private var canceled = false
var isCanceled: Bool {
updateLock.wait()
defer { updateLock.signal() }
return canceled
}
func cancel() {
updateLock.wait()
defer { updateLock.signal() }
canceled = true
}
}
// UI thread
let processingQueue = OperationQueue()
let cancelationToken = CancelationToken()
for _ in 0..100 {
processingQueue.addOperation {
// do some stuff on background thread
...
# 2
guard !cancelationToken.isCanceled else { return }
# 3
DispatchQueue.main.async {
# 4
guard !cancelationToken.isCanceled else { return }
// update UI
}
}
}
// we are still on UI thread
cancelationToken.cancel()
for operation in processingQueue.operations {
operation.waitUntilFinished() #1
}
Is #2 -> #1 -> #3 -> deadlock possible there?
swift multithreading thread-safety
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
add a comment |
0
I have multiple background threads which update the UI from time to time. I need to terminate them properly from the UI thread and be sure that there's no deadlock/race condition.
Here's an example that creates 100 operations and then terminates them:
class CancellationToken {
private let updateLock = DispatchSemaphore(value: 1)
private var canceled = false
var isCanceled: Bool {
updateLock.wait()
defer { updateLock.signal() }
return canceled
}
func cancel() {
updateLock.wait()
defer { updateLock.signal() }
canceled = true
}
}
// UI thread
let processingQueue = OperationQueue()
let cancelationToken = CancelationToken()
for _ in 0..100 {
processingQueue.addOperation {
// do some stuff on background thread
...
# 2
guard !cancelationToken.isCanceled else { return }
# 3
DispatchQueue.main.async {
# 4
guard !cancelationToken.isCanceled else { return }
// update UI
}
}
}
// we are still on UI thread
cancelationToken.cancel()
for operation in processingQueue.operations {
operation.waitUntilFinished() #1
}
Is #2 -> #1 -> #3 -> deadlock possible there?
swift multithreading thread-safety
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
add a comment |
0
0
0
I have multiple background threads which update the UI from time to time. I need to terminate them properly from the UI thread and be sure that there's no deadlock/race condition.
Here's an example that creates 100 operations and then terminates them:
class CancellationToken {
private let updateLock = DispatchSemaphore(value: 1)
private var canceled = false
var isCanceled: Bool {
updateLock.wait()
defer { updateLock.signal() }
return canceled
}
func cancel() {
updateLock.wait()
defer { updateLock.signal() }
canceled = true
}
}
// UI thread
let processingQueue = OperationQueue()
let cancelationToken = CancelationToken()
for _ in 0..100 {
processingQueue.addOperation {
// do some stuff on background thread
...
# 2
guard !cancelationToken.isCanceled else { return }
# 3
DispatchQueue.main.async {
# 4
guard !cancelationToken.isCanceled else { return }
// update UI
}
}
}
// we are still on UI thread
cancelationToken.cancel()
for operation in processingQueue.operations {
operation.waitUntilFinished() #1
}
Is #2 -> #1 -> #3 -> deadlock possible there?
swift multithreading thread-safety
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
I have multiple background threads which update the UI from time to time. I need to terminate them properly from the UI thread and be sure that there's no deadlock/race condition.
Here's an example that creates 100 operations and then terminates them:
class CancellationToken {
private let updateLock = DispatchSemaphore(value: 1)
private var canceled = false
var isCanceled: Bool {
updateLock.wait()
defer { updateLock.signal() }
return canceled
}
func cancel() {
updateLock.wait()
defer { updateLock.signal() }
canceled = true
}
}
// UI thread
let processingQueue = OperationQueue()
let cancelationToken = CancelationToken()
for _ in 0..100 {
processingQueue.addOperation {
// do some stuff on background thread
...
# 2
guard !cancelationToken.isCanceled else { return }
# 3
DispatchQueue.main.async {
# 4
guard !cancelationToken.isCanceled else { return }
// update UI
}
}
}
// we are still on UI thread
cancelationToken.cancel()
for operation in processingQueue.operations {
operation.waitUntilFinished() #1
}
Is #2 -> #1 -> #3 -> deadlock possible there?
swift multithreading thread-safety
swift multithreading thread-safety
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
edited Nov 24 '18 at 14:25
Dan Pristupov
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
asked Nov 20 '18 at 14:07
Dan PristupovDan Pristupov
1114
1114
add a comment |
add a comment |
0
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