diff options
| author | Thiago Macieira <thiago.macieira@intel.com> | 2023-03-17 13:31:36 -0700 |
|---|---|---|
| committer | Thiago Macieira <thiago.macieira@intel.com> | 2023-05-22 10:43:53 -0700 |
| commit | c5221f6be00c16187e0abf008b33c230fea56c29 (patch) | |
| tree | b0032b37677d2b307e7d1589e1eb124285b76992 /src/corelib/io/qprocess.cpp | |
| parent | f9c87cfd44bcf4b90cb45354252ef19f647b0469 (diff) | |
QProcess/Linux: add a flag to re-enable the vfork()-like semantics
Commit 29b2fe40dc778ec73da7e5643fcfd8979d8ecebc disabled it by reverting
commit d6bf71123d3ef073f25610345cb5dc920e4fb783. We now add the promised
flag to opt-in. The flag is added to all Unix systems, but it really
only applies to Linux right now.
No ChangeLog because the whole UnixProcessParameters structure is new
and has its own changelog.
Task-number: QTBUG-104493
Task-number: QTBUG-111243
Task-number: QTBUG-111964
Change-Id: Icfe44ecf285a480fafe4fffd174d4effd3382495
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Diffstat (limited to 'src/corelib/io/qprocess.cpp')
| -rw-r--r-- | src/corelib/io/qprocess.cpp | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp index ddcd7a4768a..ff33607fa16 100644 --- a/src/corelib/io/qprocess.cpp +++ b/src/corelib/io/qprocess.cpp @@ -853,6 +853,15 @@ void QProcessPrivate::Channel::clear() is useful to ensure any ignored (\c SIG_IGN) signal does not affect the child's behavior. + \value UseVFork Requests that QProcess use \c{vfork(2)} to start the child + process. Use this flag to indicate that the callback function set + with setChildProcessModifier() is safe to execute in the child side of + a \c{vfork(2)}; that is, the callback does not modify any non-local + variables (directly or through any function it calls), nor attempts + to communicate with the parent process. It is implementation-defined + if QProcess will actually use \c{vfork(2)} and if \c{vfork(2)} is + different from standard \c{fork(2)}. + \sa setUnixProcessParameters(), unixProcessParameters() */ @@ -1646,6 +1655,16 @@ std::function<void(void)> QProcess::childProcessModifier() const "async-signal-safe" is advised). Most of the Qt API is unsafe inside this callback, including qDebug(), and may lead to deadlocks. + \note If the UnixProcessParameters::UseVFork flag is set via + setUnixProcessParameters(), QProcess may use \c{vfork()} semantics to + start the child process, so this function must obey even stricter + constraints. First, because it is still sharing memory with the parent + process, it must not write to any non-local variable and must obey proper + ordering semantics when reading from them, to avoid data races. Second, + even more library functions may misbehave; therefore, this function should + only make use of low-level system calls, such as \c{read()}, + \c{write()}, \c{setsid()}, \c{nice()}, and similar. + \sa childProcessModifier(), setUnixProcessParameters() */ void QProcess::setChildProcessModifier(const std::function<void(void)> &modifier) |