why concurrentQueue.sync DON'T cause deadlock
This code will deadlock because:
- they are in same thread
- print(2) has to wait print(3)
- print(3) has to wait print(2)
For example:
DispatchQueue.main.async
print(Thread.current)
DispatchQueue.main.sync
print(Thread.current)
print(2)
print(3)
Why in the concurrentQueue won't cause deadlock? They are also in same thread.
DispatchQueue.global().async
print(Thread.current)
DispatchQueue.global().sync
print(Thread.current)
print(2)
print(3)
ios concurrency grand-central-dispatch deadlock
edited Dec 22 '18 at 2:15
Rob
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
add a comment |
This code will deadlock because:
- they are in same thread
- print(2) has to wait print(3)
- print(3) has to wait print(2)
For example:
DispatchQueue.main.async
print(Thread.current)
DispatchQueue.main.sync
print(Thread.current)
print(2)
print(3)
Why in the concurrentQueue won't cause deadlock? They are also in same thread.
DispatchQueue.global().async
print(Thread.current)
DispatchQueue.global().sync
print(Thread.current)
print(2)
print(3)
ios concurrency grand-central-dispatch deadlock
edited Dec 22 '18 at 2:15
Rob
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
add a comment |
This code will deadlock because:
- they are in same thread
- print(2) has to wait print(3)
- print(3) has to wait print(2)
For example:
DispatchQueue.main.async
print(Thread.current)
DispatchQueue.main.sync
print(Thread.current)
print(2)
print(3)
Why in the concurrentQueue won't cause deadlock? They are also in same thread.
DispatchQueue.global().async
print(Thread.current)
DispatchQueue.global().sync
print(Thread.current)
print(2)
print(3)
ios concurrency grand-central-dispatch deadlock
edited Dec 22 '18 at 2:15
Rob
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
This code will deadlock because:
- they are in same thread
- print(2) has to wait print(3)
- print(3) has to wait print(2)
For example:
DispatchQueue.main.async
print(Thread.current)
DispatchQueue.main.sync
print(Thread.current)
print(2)
print(3)
Why in the concurrentQueue won't cause deadlock? They are also in same thread.
DispatchQueue.global().async
print(Thread.current)
DispatchQueue.global().sync
print(Thread.current)
print(2)
print(3)
ios concurrency grand-central-dispatch deadlock
ios concurrency grand-central-dispatch deadlock
edited Dec 22 '18 at 2:15
Rob
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
edited Dec 22 '18 at 2:15
Rob
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
edited Dec 22 '18 at 2:15
Rob
302k49564734
edited Dec 22 '18 at 2:15
Rob
302k49564734
edited Dec 22 '18 at 2:15
Rob
302k49564734
302k49564734
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
asked Nov 14 '18 at 5:56
pangyuleipangyulei
66
66
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You ask:
Why in the
concurrentQueuewon't cause deadlock? They are also in same thread.
No, they're not in the same thread. They're in the same queue, but not the same thread.
This is the whole idea behind "concurrent queues" is that they can run individual dispatched tasks on different threads. That's how they permit concurrent operation. One dispatched task on concurrent queue can run on one thread while another dispatched task on that same queue can run on a separate thread.
As the old Concurrency Programming Guide says in its definition of a "concurrent queue":
The currently executing tasks run on distinct threads that are managed by the dispatch queue.
Or, as the DispatchQueue documentation says:
DispatchQueuemanages the execution of work items. Each work item submitted to a queue is processed on a pool of threads managed by the system. [emphasis added]
answered Dec 22 '18 at 2:13
RobRob
302k49564734
add a comment |
Your Answer
StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53293965%2fwhy-concurrentqueue-sync-dont-cause-deadlock%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You ask:
Why in the
concurrentQueuewon't cause deadlock? They are also in same thread.
No, they're not in the same thread. They're in the same queue, but not the same thread.
This is the whole idea behind "concurrent queues" is that they can run individual dispatched tasks on different threads. That's how they permit concurrent operation. One dispatched task on concurrent queue can run on one thread while another dispatched task on that same queue can run on a separate thread.
As the old Concurrency Programming Guide says in its definition of a "concurrent queue":
The currently executing tasks run on distinct threads that are managed by the dispatch queue.
Or, as the DispatchQueue documentation says:
DispatchQueuemanages the execution of work items. Each work item submitted to a queue is processed on a pool of threads managed by the system. [emphasis added]
answered Dec 22 '18 at 2:13
RobRob
302k49564734
add a comment |
You ask:
Why in the
concurrentQueuewon't cause deadlock? They are also in same thread.
No, they're not in the same thread. They're in the same queue, but not the same thread.
This is the whole idea behind "concurrent queues" is that they can run individual dispatched tasks on different threads. That's how they permit concurrent operation. One dispatched task on concurrent queue can run on one thread while another dispatched task on that same queue can run on a separate thread.
As the old Concurrency Programming Guide says in its definition of a "concurrent queue":
The currently executing tasks run on distinct threads that are managed by the dispatch queue.
Or, as the DispatchQueue documentation says:
DispatchQueuemanages the execution of work items. Each work item submitted to a queue is processed on a pool of threads managed by the system. [emphasis added]
answered Dec 22 '18 at 2:13
RobRob
302k49564734
add a comment |
You ask:
Why in the
concurrentQueuewon't cause deadlock? They are also in same thread.
No, they're not in the same thread. They're in the same queue, but not the same thread.
This is the whole idea behind "concurrent queues" is that they can run individual dispatched tasks on different threads. That's how they permit concurrent operation. One dispatched task on concurrent queue can run on one thread while another dispatched task on that same queue can run on a separate thread.
As the old Concurrency Programming Guide says in its definition of a "concurrent queue":
The currently executing tasks run on distinct threads that are managed by the dispatch queue.
Or, as the DispatchQueue documentation says:
DispatchQueuemanages the execution of work items. Each work item submitted to a queue is processed on a pool of threads managed by the system. [emphasis added]
answered Dec 22 '18 at 2:13
RobRob
302k49564734
You ask:
Why in the
concurrentQueuewon't cause deadlock? They are also in same thread.
No, they're not in the same thread. They're in the same queue, but not the same thread.
This is the whole idea behind "concurrent queues" is that they can run individual dispatched tasks on different threads. That's how they permit concurrent operation. One dispatched task on concurrent queue can run on one thread while another dispatched task on that same queue can run on a separate thread.
As the old Concurrency Programming Guide says in its definition of a "concurrent queue":
The currently executing tasks run on distinct threads that are managed by the dispatch queue.
Or, as the DispatchQueue documentation says:
DispatchQueuemanages the execution of work items. Each work item submitted to a queue is processed on a pool of threads managed by the system. [emphasis added]
answered Dec 22 '18 at 2:13
RobRob
302k49564734
edited Dec 22 '18 at 18:16
answered Dec 22 '18 at 2:13
RobRob
302k49564734
answered Dec 22 '18 at 2:13
RobRob
302k49564734
answered Dec 22 '18 at 2:13
RobRob
302k49564734
302k49564734
add a comment |
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53293965%2fwhy-concurrentqueue-sync-dont-cause-deadlock%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
