QPromise and QFuture created from it share the same internal state
(namely, QFutureInterface object). QPromise provides high-level
management of the shared resource, ensuring thread-safe behavior
on construction and destruction (also taking into account
QFuture::waitForFinished() semantics).
QFuture acts as a primary controller of QPromise via action
initiating methods such as suspend() or cancel(). QPromise is
equipped with methods to check the status, but the actual
handling of QFuture action "requests" is user-defined.
[ChangeLog][QtCore][QPromise] Added QPromise class to accompany
QFuture. It allows one to communicate computation results and
progress to the QFuture via a shared state.
Task-number: QTBUG-81586
Change-Id: Ibab9681d35fe63754bf394ad0e7923e2683e2457
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Deprecated the pause-related APIs of QFuture* classes and
added alternatives having "suspend" in the name instead.
With 2f15927f01ceef0aca490746302a5ea57ea9441c new
isSuspended()/suspended() APIs have been added to QFuture* classes for
checking if pause/suspension is still in progress or it already took
effect. To keep the naming more consistent, renamed:
- setPaused() -> setSuspended()
- pause() -> suspend()
- togglePaused() -> toggleSuspended()
- QFutureWatcher::paused() -> QFutureWatcher::suspending()
Note that QFuture*::isPaused() now corresponds to (isSuspending() ||
isSuspended()).
[ChangeLog][Deprecation Notice] Deprecated pause-related APIs of
QFuture and QFutureWatcher. Added alternatives having "suspend" in
the name instead.
Change-Id: Ibeb75017a118401d64d18b72fb95d78e28c4661c
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Because setting QFutureInterface to paused state does not mean that
the computations that are already in progress will stop immediately,
it may be useful to get notified when pause actually takes effect.
Introduced the QFutureWatcher::suspended() signal, to be emitted when
there are no more computations in progress, and no more result ready
or progress reporting signals will be emitted, i.e. when pause took
effect. Added {QFuture, QFutureWatcher}::isSuspended() methods for
checking if pause took effect.
QtConcurrent will now to send QFutureCallOutEvent::Suspended event
when the state is paused and there are no more active threads.
[ChangeLog][QtCore][QFutureWatcher] Added a new QFutureWatcher::suspended()
signal, to be emitted when pause took effect, meaning that there are no
more computations in progress. Added {QFuture, QFutureWatcher}::isSuspended()
methods for checking if pause took effect.
Fixes: QTBUG-12152
Change-Id: I88f2ad24d800cd6293dec63977d45bd35f9a09f0
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Replaced the internal ExceptionHolder for storing QException* by
std::exception_ptr. This will allow to report and store exceptions
of types that are not derived from QException.
Task-number: QTBUG-81588
Change-Id: I96be919d8289448b3e608310e51a16cebc586301
Reviewed-by: Vitaly Fanaskov <vitaly.fanaskov@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
QFuture's original design pre-dates C++11 and its
introduction of move semantics. QFuture is documented
as requiring copy-constructible classes and uses copy
operations for results (which in Qt's universe in general
is relatively cheap, due to the use of COW/data sharing).
QFuture::result(), QFuture::results(), QFuture::resultAt()
return copies. Now that the year is 2020, it makes some
sense to add support for move semantics and, in particular,
move-only types, like std::unique_ptr (that cannot be
obtained from QFuture using result etc.). Taking a result
or results from a QFuture renders it invalid. This patch
adds QFuture<T>::takeResults(), takeResult() and isValid().
'Taking' functions are 'enabled_if' for non-void types only
to improve the compiler's diagnostic (which would otherwise
spit some semi-articulate diagnostic).
As a bonus a bug was found in the pre-existing code (after
initially copy and pasted into the new function) - the one
where we incorrectly report ready results in (rather obscure)
filter mode.
Fixes: QTBUG-81941
Fixes: QTBUG-83182
Change-Id: I8ccdfc50aa310a3a79eef2cdc55f5ea210f889c3
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Added QFuture::then() methods to allow chaining multiple asynchronous
computations.
Continuations can use the following execution policies:
* QtFuture::Launch::Sync - the continuation will be launched in the same
thread in which the parent has been executing.
* QtFuture::Launch::Async - the continuation will be launched in a new
thread.
* QtFuture::Launch::Inherit - the continuation will inherit the launch
policy of the parent, or its thread pool (if it was using a custom one).
* Additionally then() also accepts a custom QThreadPool* instance.
Note, that if the parent future gets canceled, its continuation(s) will
be also canceled.
If the parent throws an exception, it will be propagated to the
continuation's future, unless it is caught inside the continuation
(if it has a QFuture arg).
Some example usages:
QFuture<int> future = ...;
future.then([](int res1){ ... }).then([](int res2){ ... })...
QFuture<int> future = ...;
future.then([](QFuture<int> fut1){ /* do something with fut1 */ })...
In the examples above all continuations will run in the same thread as
future.
QFuture<int> future = ...;
future.then(QtFuture::Launch::Async, [](int res1){ ... })
.then([](int res2){ ... })..
In this example the continuations will run in a new thread (but on the
same one).
QThreadPool pool;
QFuture<int> future = ...;
future.then(&pool, [](int res1){ ... })
.then([](int res2){ ... })..
In this example the continuations will run in the given thread pool.
[ChangeLog][QtCore] Added support for attaching continuations to QFuture.
Task-number: QTBUG-81587
Change-Id: I5b2e176694f7ae8ce00404aca725e9a170818955
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Move away from using 0 as pointer literal.
Done using clang-tidy. This is not complete as
run-clang-tidy can't handle all of qtbase in one go.
Change-Id: I1076a21f32aac0dab078af6f175f7508145eece0
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Ditch the QMutex *mutex() method that we had to keep around for binary
compatibility and drop the disambiguation argument of QMutex
&mutex(int) now that we don't need it anymore.
The lock_guard lines now look dangerously close to C++'s Most Vexing
Parse, so use braced initialization to make sure it's parsed as a
definition, not a declaration.
Change-Id: Ie3d70f58c9878ab6d7da8f8bd72a4cb4aff83bb7
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
We can't use qt_scoped_lock/qt_unique_lock here, so port to
std::unique_lock and std::lock_guard for now.
This is in preparation of deprecating QMutexLocker in favor
of std::unique_lock and std::scoped_lock.
In QFutureInterface, change the return type of mutex() from
QMutex* to QMutex&, so we don't need to deref when passing
to std::lock_guard. We need to keep the old method around
for BC reasons, so the new one needs an artificial function
argument for disambiguation. This will vanish come Qt 6.
Change-Id: I1a0f0205952a249512ec2dbd3f0f48dd209b1636
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Semi-automated, just needed ~20 manual fixes:
$ find \( -iname \*.cpp -or -iname \*.h \) -exec perl -pe 's/(\.|->)load\(\)/$1loadRelaxed\(\)/g' -i \{\} +
$ find \( -iname \*.cpp -or -iname \*.h \) -exec perl -pe 's/(\.|->)store\(/$1storeRelaxed\(/g' -i \{\} +
It can be easily improved (e.g. for store check that there are no commas
after the opening parens). The most common offender is QLibrary::load,
and some code using std::atomic directly.
Change-Id: I07c38a3c8ed32c924ef4999e85c7e45cf48f0f6c
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
After including windows.h, interface is a define that expands to
"struct" (unless WIN32_LEAN_AND_MEAN is defined). This name is
used as a normal identifier in multiple places within Qt.
This has already been worked around in a number of places
(in e.g. 3ba61d9baa569ea69e41a943981680c09c521ff7 and
786d23bb4966b6697ac04c43158e2312d898e133).
After qrandom.h was included in <QtCore/QtCore>, this header
implicitly includes <random>. In libc++ on windows, this header
then transitively includes windows.h, exposing the clash with
the name "interface" in even more locations than before.
For cases within qtbase internals, it could also alternatively be
handled by defining WIN32_LEAN_AND_MEAN while building QtDbus, but
for occurrences in public headers, the undef trick needs to be
used.
Change-Id: I89754f38f55ae7f2145255a2c8a71b23492be6a1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
... and make sure we can compile without it. In particular,
Qt Concurrent depends on QFuture, so we specify it as a condition,
and QtConcurrentException should not depend on future but on
concurrent.
Change-Id: I65b158021cecb19f227554cc8b5df7a139fbfe78
Reviewed-by: Martin Smith <martin.smith@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Introduce helper functions switch_{on,off,from_to} to make
the code more readable, and prepare everything for later
optimizations reducing the sizes of critical sections (by
locking the mutex later, or even never).
This commit, however, is only concerned with shutting up
tsan.
In waitForResult(), simplified the code by removing an
unneeded if guard: the condition is checked in the while
loop immediately following in the then-block, and the
local variable declaration that precedes the loop is not
worth guarding.
Change-Id: I24bfd864ca96f862302536ad8662065e6f366fa8
Reviewed-by: David Faure <david.faure@kdab.com>
This fixes a problem that occurs when a task, that is run synchronously,
throws an exception. If that happened, then the exception would not be
re-thrown, because of an early return.
Task-number: QTBUG-54831
Change-Id: Ic70c5b810ec6adce6e62bfd6832ba9f170b13a7f
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>
These variables are accessed from both the executing
thread as well as the thread waiting for results.
Note for some variables which threads access them.
Change-Id: I1c84ddff92585abb32341c42072106066e485f7e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
From Qt 5.7 -> LGPL v2.1 isn't an option anymore, see
http://blog.qt.io/blog/2016/01/13/new-agreement-with-the-kde-free-qt-foundation/
Updated license headers to use new LGPL header instead of LGPL21 one
(in those files which will be under LGPL v3)
Change-Id: I046ec3e47b1876cd7b4b0353a576b352e3a946d9
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Qt copyrights are now in The Qt Company, so we could update the source
code headers accordingly. In the same go we should also fix the links to
point to qt.io.
Outdated header.LGPL removed (use header.LGPL21 instead)
Old header.LGPL3 renamed to header.LGPL3-COMM to match actual licensing
combination. New header.LGPL-COMM taken in the use file which were
using old header.LGPL3 (src/plugins/platforms/android/extract.cpp)
Added new header.LGPL3 containing Commercial + LGPLv3 + GPLv2 license
combination
Change-Id: I6f49b819a8a20cc4f88b794a8f6726d975e8ffbe
Reviewed-by: Matti Paaso <matti.paaso@theqtcompany.com>
[ChangeLog][QtCore][QThreadPool] Added QThreadPool::cancel() which allows
removing from the job queue a job that hasn't been started yet.
Change-Id: Ib8f1c1f32a34f5eec8338c641d820b928e470164
Reviewed-by: Nick Shaforostoff <shafff@ukr.net>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Background:
It is often necessary/advisable to schedule tasks on thread pools !=
globalInstance(). As Herb Sutter writes in
http://www.drdobbs.com/parallel/use-thread-pools-correctly-keep-tasks-sh/216500409
and the Qt Training Material stresses, tasks you schedule on a (global)
thread pool should be non-blocking, which currently rules out using any of
the QtConcurrent functions for, say, file I/O.
Nonetheless it's often convenient to have thread pools also for file I/O, as
the thumbnail viewer exercise in the Qt Training Material shows. In this
case, you'd use a dedicated thead pool, leaving the global thread pool for
CPU-bound tasks.
Yet, none of the QtConcurrent functions allow to pick the QThreadPool
instance on which to schedule the work created with them.
This patch prepares for them to do so.
This is the first part of the forward-port of
https://qt.gitorious.org/qt/qt/merge_requests/1281.
Implement by using a new QThreadPool* member that defaults to nullptr,
and adding setThreadPool to set this member, then using it in lieu of
QThreadPool::globalInstance() everywhere.
I chose to leave m_pool == nullptr to mean globalInstance() to avoid
creating the global instance whenever a QFuture is created, even if the
future represents the result of a calculation not run on the global thread
pool.
[ChangeLog][QtCore][QFuture] Can now be used with any QThreadPool, not
just globalInstance().
Task-number: QTBUG-17220
Change-Id: I4e1dc18d55cf60141b2fa3d14e2d44a3e9e74858
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Rationale: a wait on a condition-variable is usually a cancellation point.
On Posix, and probably in C++ at some point, a thread cancellation is
done by (a kind of) exception unwinding the stack. To ensure that
we call reserveThread() in all cases, wrap the function pair in a RAII
class. Even if we currently don't seem to support exceptions in QtCore,
this is low-hanging fruit, and no worse than what we had before.
Change-Id: Ifb0f428ea50f9ac12be14e620615f46e00d3dd91
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Remove all trailing whitespace from the following list of files:
*.cpp *.h *.conf *.qdoc *.pro *.pri *.mm *.rc *.pl *.qps *.xpm *.txt *README
excluding 3rdparty, test-data and auto generated code.
Note A): the only non 3rdparty c++-files that still
have trailing whitespace after this change are:
* src/corelib/codecs/cp949codetbl_p.h
* src/corelib/codecs/qjpunicode.cpp
* src/corelib/codecs/qbig5codec.cpp
* src/corelib/xml/qxmlstream_p.h
* src/tools/qdoc/qmlparser/qqmljsgrammar.cpp
* src/tools/uic/ui4.cpp
* tests/auto/other/qtokenautomaton/tokenizers/*
* tests/benchmarks/corelib/tools/qstring/data.cpp
* util/lexgen/tokenizer.cpp
Note B): in about 30 files some overlapping 'leading tab' and
'TAB character in non-leading whitespace' issues have been fixed
to make the sanity bot happy. Plus some general ws-fixes here
and there as asked for during review.
Change-Id: Ia713113c34d82442d6ce4d93d8b1cf545075d11d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Following 731ba8ed08f80644b403556638c7f6229e678ebe this function is
not used anymore
Change-Id: Id908931b4b21c825bd80a4f03790630818c73c07
Reviewed-by: Christian Stromme <christian.stromme@digia.com>
To avoid leaking when converting a QFuture<T> to a QFuture<void> we need
to have a separate ref. counter for QFuture<T>. When the last QFuture<T>
goes out of scope, we need to clean out the result data.
Task-number: QTBUG-27224
Change-Id: I965a64a11fffbb191ab979cdd030a9aafd4436c2
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
This class belongs to QThreadPool/QRunnable more than to QtConcurrent, so
move to QtCore, where QThreadPool awaits it.
Change-Id: Ibf20288a986593bf779453427c2dae8db1e1423a
Reviewed-by: Qt Doc Bot <qt_docbot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
