Change the title.
Remove the first \brief as there are two briefs in the document
so that the new title makes sense with the second brief in
"All Qt Examples" doc page.
Task-number: QTBUG-108859
Pick-to: 6.6 6.5
Change-Id: I8b0370c9a85179e172918231ae48a3c52845bf21
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Notification of a conditional variable shouldn't be under the locked
mutex, as it may affect extra mutex contentions.
Pick-to: 6.5 6.6
Change-Id: Ie8429eca3f36e9a6e8e5ad2e0337bbf508f5b326
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This allows us to use absolute times on Linux (today) and FreeBSD
(soon), plus simplifies both QMutex and QSemaphore.
Change-Id: I63b988479db546dabffcfffd17675a182aa528fa
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Fixes GCC 11 C++17 unity-build (didn't investigate which one is the
problem) error:
qsemaphore.cpp:275:7: error: ‘QSemaphorePrivate’ has a base ‘{anonymous}::QtSemaphorePrivate::Layout1’ whose type uses the anonymous namespace [-Werror=subobject-linkage]
275 | class QSemaphorePrivate : public QtSemaphorePrivate::Members
| ^~~~~~~~~~~~~~~~~
Amends fbc491230fe62f739925e8113d05f4108e2738ef.
Change-Id: I3b95a35822ec62aabd4c310b02bf58679bb9651f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
They existed because INTEGRITY hadn't yet been updated to the C++11
Standard Library, with a minor for broken MinGW cross-compilation builds
that forgot to enable gthreads support in libstdc++. The former appears
to have been since fixed and the latter is a massive toolchain
configuration mistake.
Change-Id: I63b988479db546dabffcfffd1766b55132371f9b
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
They are now ordered so that the mutex and the wait condition are in
different cache lines, to avoid false sharing situations, if the types
are holding the actual threading primitive structures, not mere pointers
to some other structure elsewhere.
For 64-bit systems:
OS | mutex | cond | Remark
--------------------+-------+-------+------------------
Darwin | 64 | 48 |
FreeBSD | 8 | 8 |
INTEGRITY | 8 | 8 | QMutex & QWaitCondition
Linux | 24 | 48 | Always uses futex
MinGW (Winpthreads) | 8 | 8 | Always uses futex
MSVC (MS STL) | 32 | 16 | Always uses futex
NetBSD | 48 | 40 |
OpenBSD | 8 | 8 |
QNX | ? | ? |
Change-Id: I63b988479db546dabffcfffd176698e4f0097e90
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
futexSemaphoreTryAcquire_loop() always waits on 32-bit portions of
QSemaphore. The current implementations only look at the pointer address
and don't care what size the waiter used. That's not the case for the
Darwin/macOS implementation:
In xnu/bsd/kern/sys_ulock.c:ulock_wake[1]:
if (opcode != ull->ull_opcode) {
ret = EDOM;
goto out_ull_put;
}
[1] 5c2921b07a/bsd/kern/sys_ulock.c (L970-L973)
Change-Id: I63b988479db546dabffcfffd1766c5eae61187f0
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
The QSemaphore acquire & release functions, plus the constructor and
destructor, can be made noexcept on platforms that use futexes
(currently, Linux and Windows; likely macOS by the time we make 7.0). I
didn't make the change right now because the acquire and release
functions have narrow contracts on the int n values. I didn't make that
change now because it make a mess of the code, for little gain as this
class isn't used that often.
Plus, we may want to investigate whether we want to keep the multi-token
semaphore functionality around (something neither POSIX sem_t nor
std::counting_semaphore have), or split that off into a separate class
like QBasicMutex / QMutex / QRecursiveMutex was done.
Change-Id: Ieab617d69f3b4b54ab30fffd175b27813728f2ce
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
This removes the last use of QtPrivate::convertToMilliseconds().
Change-Id: I6f518d59e63249ddbf43fffd1759fee2e00d36f4
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
error: right shift count >= width of type [-Werror=shift-count-overflow]
Pick-to: 6.4
Fixes: QTBUG-105687
Change-Id: Ic6547f8247454b47baa8fffd170bd9cd0e2a8ca3
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Found by codespell
Pick-to: 6.4
Change-Id: Ie3e301a23830c773a2e9aff487c702a223d246eb
Reviewed-by: Nicholas Bennett <nicholas.bennett@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Replace the current license disclaimer in files by
a SPDX-License-Identifier.
Files that have to be modified by hand are modified.
License files are organized under LICENSES directory.
Task-number: QTBUG-67283
Change-Id: Id880c92784c40f3bbde861c0d93f58151c18b9f1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
The std variant is faster and more compact.
Use the QtPrivate wrappers to avoid the Integrity mess.
Change-Id: I4a1b1626d29472af059fee55ca26c31d9522b179
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Add one and reset the wakeAll bit atomically.
This avoids a race in a case where an acquiring thread
is owning the semaphore, and deleting it after a
set number of releases (one for each thread referencing the semaphore).
Two releasing threads could enter the if statement under
futexNeedsWake(prevValue), the counter been incremented at
this point and reached the value being acquired, meaning the thread
acquiring can be awakened by just one of the two releasers,
delete the semaphore, and then the second releaser would access
the now deleted semaphore.
The patch avoids that by unsetting and reading the wakeAll bit
atomically, so only one thread will try to wake all threads.
Pick-to: 6.3 6.2 5.15
Fixes: QTBUG-102484
Change-Id: I32172ed44d74378c627918e19b9e1aaadb5c6d1d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
src/corelib/kernel/qmetatype.cpp:1605: (qdoc) warning: Command '\snippet (//! [[implicit]])' failed at end of file 'qmetatyp>
src/corelib/kernel/qmetatype.cpp:1615: (qdoc) warning: Command '\snippet (//! [[member]])' failed at end of file 'qmetatype/>
src/corelib/kernel/qmetatype.cpp:1626: (qdoc) warning: Command '\snippet (//! [[memberOk]])' failed at end of file 'qmetatyp>
src/corelib/kernel/qmetatype.cpp:1639: (qdoc) warning: Command '\snippet (//! [[unaryfunc]])' failed at end of file 'qmetaty>
src/corelib/text/qbytearraymatcher.cpp:233: (qdoc) warning: No such parameter 'view' in QByteArrayMatcher::indexIn()
src/corelib/time/qdatetime.cpp:1854: (qdoc) warning: Can't link to 'QLocaleie:pmText()'
src/corelib/thread/qsemaphore.cpp:494: (qdoc) warning: Undocumented return value (hint: use 'return' or 'returns' in the text
src/corelib/thread/qsemaphore.cpp:505: (qdoc) warning: Undocumented parameter 'timeout' in QSemaphore::try_acquire_for()
src/corelib/thread/qsemaphore.cpp:505: (qdoc) warning: Undocumented return value (hint: use 'return' or 'returns' in the text
src/corelib/thread/qsemaphore.cpp:516: (qdoc) warning: Undocumented parameter 'tp' in QSemaphore::try_acquire_until()
src/corelib/thread/qsemaphore.cpp:516: (qdoc) warning: Undocumented return value (hint: use 'return' or 'returns' in the text
Change-Id: Ib612c69525ec7542f2ad3dd9a07e89f266718fd8
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
std::chrono values are passed by const reference.
Still warnings from undocumented parameters, but rephrasing
the documentation doesn't make it better in this case, so perhaps
qdoc needs a way to suppress the warning. Adding an \omit block
where the parameters or return values are mentioned doesn't help.
Change-Id: I7d495d73d8367d9d90dd33a4880ac7c978382d19
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
... and C++20 std::counting_semaphore API compatibility.
[ChangeLog][QtCore][QSemaphore] tryAcquire() now optionally takes a
<chrono> duration as timeout, not just int milliseconds.
[ChangeLog][QtCore][QSemaphore] Added try_acquire{,_for,_until}() for
C++20 std::counting_semaphore compatibility.
Change-Id: I34b6b4bf57a54745d4b97349903d090c4995338a
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Either the mix of futex and atomic, or the mix of 32-bit futex and
64-bit atomic doesn't work. In any case, the existing code leads to
bad behavior.
Pick-to: 6.1 5.15
Fixes: QTBUG-92188
Change-Id: Icc6ba28d6e2465c373d00e84f4da2b92c037e797
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
It was mistaking semaphore values over 0 as waiters, regardless of
actual waiters.
Pick-to: 6.1
Change-Id: Icebd01592ca8bdc1687a29dc569e3b630a262606
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
We do this by making the 'futexNeedsWakeAllBit' to be part of both the
expectedValue and the pointer we're waiting on.
This makes sense since having the 'futexNeedsWakeAllBit' set is a
requirement for starting a sleep. Thus we should condition
sleeping on whether or not another thread unset it.
Since the futexNeedsWakeAllBit is in the "topmost" bit of the pointer we
wait on we'll need to use the full 64-bits on 64-bit platforms.
This isn't enabled (nor was it an issue) for configurations with
'futexHasWaiterCount' since that works differently, and waits for the
high 32 bits.
Fixes: QTBUG-92148
Change-Id: I424c605f0120ea5e647c5bb19b00ff35eaf1608a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
We might return false a few lines down, without decreasing the count.
Change-Id: I0a90c07f279860987e41539e9d5f3b5d2cb15207
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This reverts commit ff69227a49119c00f703cf89c9d72db7eeeeaa66.
Reason for revert: 64-bit atomics on 32-bit systems are often
(but not always) worse than the 32-bit semaphore as it was
implemented. Plus the High32 and Low32 functions are returning
the same thing, forgetting the endianness check.
Change-Id: I5d5ade6e9bc7086600ff2302546385151e32142b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
This simplifies the implementation so that we don't
need separate code paths for 32 and 64 bit anymore.
Change-Id: I823612865e7d648fb0bd1632385ce67b5a452b8a
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Both normal and relaxed constexpr are required by our new minimum of
C++17.
Change-Id: Ic028b88a2e7a6cb7d5925f3133b9d54859a81744
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
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>
Replace null and '\c nullptr' with \nullptr in the documentation.
Change-Id: Ib9e0cfc2eb2830b213e6523773603d56180b0998
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
We need to override this snippet for the documentation
we generate for Qt for Python, and it is easier to have
it on a separate file.
Task-number: PYSIDE-801
Task-number: PYSIDE-691
Change-Id: Ideb5b6af25024279f167137d3b65660bb9c96a7e
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Add it to configure.json and replace all occurrences of QT_NO_THREAD
with QT_CONFIG(thread). Add conditions for other features that depend
on thread support. Remove conditions where we can use the QMutex and
QThreadStorage stubs.
Change-Id: I284e5d794fda9a4c6f4a1ab29e55aa686272a0eb
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
The original design for the 64-bit futex had the token count replicated
in the high part. But the constructor wasn't setting it. This is one of
the issues I had noticed when investigating QTBUG-66875, but didn't need
to address since the the fix I ended up applying in commit
081c001deb75fa38385d3ff8cbbdb4f788529133 made that unnecessary: the high
part only had the number of waiters.
Unfortunately, when commit f502270c0f06daba75c1da381bd1658d81aa7bba
brought back the token count in the high part, I failed to correct that
problem. As a consequence, every QSemaphore that was initialized in the
constructor to a non-zero value would eventually deadlock.
This commit fixes that oversight.
Task-number: QTBUG-67481
Change-Id: I662b8f168c74440ab1a8fffd1522be6b85adb4d0
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Svenn-Arne Dragly <svenn-arne.dragly@qt.io>
This time, the issue was that we could race a wait and a wake. A multi-
token waiter would not notice that the number of tokens changed because
it only performed a fetch-and-OR, then waited on the high part which did
not change. That means the futex_wait() would succeed, when we wanted it
to have failed.
So we have to bring back a portion of what commit
081c001deb75fa38385d3ff8cbbdb4f788529133 removed: we need to keep both
the token count and the waiter count in the high word.
Task-number: QTBUG-67214
Change-Id: I04a43ee94975482f9e32fffd151e467a9e0030b3
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Since we won't use the high bit of the low 32-bit word at all, we don't
need the AND with 0x7fffffff either. Just cast.
Change-Id: I72f5230ad59948f784eafffd151aa5a7dee995db
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
When the thread that got woken up by release() is supposed to release()
to wake up another thread, we were deadlocking. This happened because we
cleared the bit indicating that there was contention when the first
release(). Instead of storing a single bit, we now store the number of
threads waiting.
Task-number: QTBUG-66875
Change-Id: I72f5230ad59948f784eafffd15193873502ecba4
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Since pthread_cond_timedwait takes absolute time instead of relative
time like most POSIX API, there's a small gain in performance here: we
avoid an extra system call to get the current time.
Task-number: QTBUG-64266
Change-Id: I25d85d86649448d5b2b3fffd1451138568091f50
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
The issue was introduced by eaee1209f0ead5be786e81db8aee604ccfea85b0, so
it affected only 5.9.2.
[ChangeLog][QtCore][QSemaphore] Fixed a regression that would make
tryAcquire() not to wait forever if the timeout was a negative
value. Note: new code is advised to only use -1 to indicate "forever",
as some other functions taking timeout periods do not accept other
values.
Task-number: QTBUG-64413
Change-Id: I57a1bd6e0c194530b732fffd14f58fce60d5dfc9
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
We don't actually need it in that case, but as the code that uses it is
disabled by a constant expression we cannot disable the variable itself
by a macro. The static_cast makes sure the compiler does not complain
about implicitly casting a 64bit value to a 32bit one.
thread/qsemaphore.cpp:156:59: error: large integer implicitly truncated to unsigned type [-Werror=overflow]
Task-number: QTBUG-64261
Change-Id: I96f53e28b290e57033737b4f994f8af5b5666587
Reviewed-by: Liang Qi <liang.qi@qt.io>
By judiciously positioning of the bits, we can optimize for the case of
threads trying to acquire a single token, which is what QSemaphore
should be mostly used for, as it matches the POSIX Semaphore API
(sem_wait, sem_timedwait and sem_trywait). If there are only waiters
waiting for a single token, we know that adding n tokens means n threads
can wake up.
This optimizes for multi-token waiters too. For example, if we have 50
single-token waiters and 50 multi-token waiters, a sem.release(5) will
wake up 55 threads instead of 100.
Change-Id: I209fcd5dbc2b4e5381cffffd14de5550c75d2600
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This is interesting because QSemaphore now needs to allocate no memory:
it's just a simple 31-bit counter and the contention flag.
Change-Id: I6e9274c1e7444ad48c81fffd14dbc0ab42bc2e00
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
