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Fix thread-safety of qt_ignore_sigpipe

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The testAndSet operation would mean another thread could see the value
of 1 and proceed to write(2)/sendto(2) before SIGPIPE had been ignored.
If the pipe or socket were already closed by then, a SIGPIPE would be
delivered to the application with its default action: terminate.

Change-Id: I62dc8f5fa14c1dd453d13e4053c642bd78fbc468
Reviewed-by: Qt Doc Bot <qt_docbot@qt-project.org>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Shane Kearns <shane.kearns@accenture.com>
Reviewed-by: Peter Hartmann <phartmann@rim.com>
This commit is contained in:
Thiago Macieira 2012-09-11 15:36:54 +02:00 committed by The Qt Project
parent 849f1f9efd
commit 3f970c20f9
2 changed files with 10 additions and 2 deletions
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6
src/corelib/io/qprocess_unix.cpp
View File

@ -953,11 +953,15 @@ static void qt_ignore_sigpipe()
{
// Set to ignore SIGPIPE once only.
static QBasicAtomicInt atom = Q_BASIC_ATOMIC_INITIALIZER(0);
if (atom.testAndSetRelaxed(0, 1)) {
if (!atom.load()) {
// More than one thread could turn off SIGPIPE at the same time
// But that's acceptable because they all would be doing the same
// action
struct sigaction noaction;
memset(&noaction, 0, sizeof(noaction));
noaction.sa_handler = SIG_IGN;
::sigaction(SIGPIPE, &noaction, 0);
atom.store(1);
}
}

6
src/network/socket/qnativesocketengine_unix.cpp
View File

@ -103,11 +103,15 @@ static void qt_ignore_sigpipe()
#ifndef Q_NO_POSIX_SIGNALS
// Set to ignore SIGPIPE once only.
static QBasicAtomicInt atom = Q_BASIC_ATOMIC_INITIALIZER(0);
if (atom.testAndSetRelaxed(0, 1)) {
if (!atom.load()) {
// More than one thread could turn off SIGPIPE at the same time
// But that's acceptable because they all would be doing the same
// action
struct sigaction noaction;
memset(&noaction, 0, sizeof(noaction));
noaction.sa_handler = SIG_IGN;
::sigaction(SIGPIPE, &noaction, 0);
atom.store(1);
}
#else
// Posix signals are not supported by the underlying platform