implement POSIX IPC based QSystemSemaphore and QSharedMemory backends

Merge-request: 1259
Reviewed-by: Harald Fernengel <harald.fernengel@nokia.com>

7 files changed, 293 insertions, 5 deletions

diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 08f9eb0..c927556 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -2747,12 +2747,10 @@ QT_LICENSED_MODULE(DBus)
 #endif
 
 #ifdef Q_OS_QNX
-// QNX doesn't have SYSV style shared memory. Multiprocess QWS apps,
-// shared fonts and QSystemSemaphore + QSharedMemory are not available
+// QNX doesn't have SYSV style shared memory. Multiprocess QWS apps
+// and shared fonts are not available
 #  define QT_NO_QWS_MULTIPROCESS
 #  define QT_NO_QWS_SHARE_FONTS
-#  define QT_NO_SYSTEMSEMAPHORE
-#  define QT_NO_SHAREDMEMORY
 #endif
 
 #if defined (__ELF__)
diff --git a/src/corelib/kernel/qsharedmemory.cpp b/src/corelib/kernel/qsharedmemory.cpp
index 2882279..371974c 100644
--- a/src/corelib/kernel/qsharedmemory.cpp
+++ b/src/corelib/kernel/qsharedmemory.cpp
@@ -80,6 +80,8 @@ QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
     return result;
 #elif defined(Q_OS_SYMBIAN)
     return result.left(KMaxKernelName);
+#elif defined(QT_POSIX_IPC)
+    return QLatin1Char('/') + result;
 #else
     return QDir::tempPath() + QLatin1Char('/') + result;
 #endif
@@ -117,6 +119,9 @@ QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
   process crashes without running the QSharedMemory destructor, the
   shared memory segment survives the crash.
 
+  \o QNX: Due to possible race conditions in the POSIX IPC implementation, create()
+  should be called prior to any attach() calls (even across multiple threads).
+
   \o HP-UX: Only one attach to a shared memory segment is allowed per
   process. This means that QSharedMemory should not be used across
   multiple threads in the same process in HP-UX.
diff --git a/src/corelib/kernel/qsharedmemory_p.h b/src/corelib/kernel/qsharedmemory_p.h
index 21b8612..780e52e 100644
--- a/src/corelib/kernel/qsharedmemory_p.h
+++ b/src/corelib/kernel/qsharedmemory_p.h
@@ -135,6 +135,8 @@ public:
             const QString &prefix = QLatin1String("qipc_sharedmemory_"));
 #ifdef Q_OS_WIN
     HANDLE handle();
+#elif defined(QT_POSIX_IPC)
+    int handle();
 #else
     key_t handle();
 #endif
@@ -166,6 +168,8 @@ private:
     HANDLE hand;
 #elif defined(Q_OS_SYMBIAN)
     RChunk chunk;
+#elif defined(QT_POSIX_IPC)
+    int hand;
 #else
     key_t unix_key;
 #endif
diff --git a/src/corelib/kernel/qsharedmemory_unix.cpp b/src/corelib/kernel/qsharedmemory_unix.cpp
index e991ce9..a086acd 100644
--- a/src/corelib/kernel/qsharedmemory_unix.cpp
+++ b/src/corelib/kernel/qsharedmemory_unix.cpp
@@ -50,8 +50,12 @@
 #ifndef QT_NO_SHAREDMEMORY
 #include <sys/types.h>
 #include <sys/ipc.h>
+#ifndef QT_POSIX_IPC
 #include <sys/shm.h>
+#else
+#include <sys/mman.h>
 #include <sys/stat.h>
+#endif
 #include <fcntl.h>
 #include <unistd.h>
 #endif // QT_NO_SHAREDMEMORY
@@ -70,7 +74,11 @@ QSharedMemoryPrivate::QSharedMemoryPrivate()
 #ifndef QT_NO_SYSTEMSEMAPHORE
       systemSemaphore(QString()), lockedByMe(false),
 #endif
+#ifndef QT_POSIX_IPC
       unix_key(0)
+#else
+      hand(0)
+#endif
 {
 }
 
@@ -91,12 +99,18 @@ void QSharedMemoryPrivate::setErrorString(const QString &function)
         errorString = QSharedMemory::tr("%1: doesn't exist").arg(function);
         error = QSharedMemory::NotFound;
         break;
+    case EAGAIN:
     case EMFILE:
+    case ENFILE:
     case ENOMEM:
     case ENOSPC:
         errorString = QSharedMemory::tr("%1: out of resources").arg(function);
         error = QSharedMemory::OutOfResources;
         break;
+    case EOVERFLOW:
+        errorString = QSharedMemory::tr("%1: invalid size").arg(function);
+        error = QSharedMemory::InvalidSize;
+        break;
     default:
         errorString = QSharedMemory::tr("%1: unknown error %2").arg(function).arg(errno);
         error = QSharedMemory::UnknownError;
@@ -112,6 +126,7 @@ void QSharedMemoryPrivate::setErrorString(const QString &function)
 
     If not already made create the handle used for accessing the shared memory.
 */
+#ifndef QT_POSIX_IPC
 key_t QSharedMemoryPrivate::handle()
 {
     // already made
@@ -140,6 +155,20 @@ key_t QSharedMemoryPrivate::handle()
     }
     return unix_key;
 }
+#else
+int QSharedMemoryPrivate::handle()
+{
+    // don't allow making handles on empty keys
+    QString safeKey = makePlatformSafeKey(key);
+    if (safeKey.isEmpty()) {
+        errorString = QSharedMemory::tr("%1: key is empty").arg(QLatin1String("QSharedMemory::handle"));
+        error = QSharedMemory::KeyError;
+        return 0;
+    }
+
+    return 1;
+}
+#endif // QT_POSIX_IPC
 
 #endif // QT_NO_SHAREDMEMORY
 
@@ -155,6 +184,7 @@ key_t QSharedMemoryPrivate::handle()
 */
 int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
 {
+#ifndef QT_POSIX_IPC
     if (QFile::exists(fileName))
         return 0;
 
@@ -168,6 +198,11 @@ int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
         qt_safe_close(fd);
     }
     return 1;
+#else
+    Q_UNUSED(fileName);
+    // nothing to do
+    return -1;
+#endif
 }
 #endif // QT_NO_SHAREDMEMORY && QT_NO_SYSTEMSEMAPHORE
 
@@ -175,11 +210,17 @@ int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
 
 void QSharedMemoryPrivate::cleanHandle()
 {
+#ifndef QT_POSIX_IPC
     unix_key = 0;
+#else
+    qt_safe_close(hand);
+    hand = 0;
+#endif
 }
 
 bool QSharedMemoryPrivate::create(int size)
 {
+#ifndef QT_POSIX_IPC
     // build file if needed
     int built = createUnixKeyFile(nativeKey);
     if (built == -1) {
@@ -211,12 +252,46 @@ bool QSharedMemoryPrivate::create(int size)
             QFile::remove(nativeKey);
         return false;
     }
+#else
+    if (!handle())
+        return false;
+
+    QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+
+    int fd;
+    EINTR_LOOP(fd, shm_open(shmName.constData(), O_RDWR | O_CREAT | O_EXCL, 0666));
+    if (fd == -1) {
+        QString function = QLatin1String("QSharedMemory::create");
+        switch (errno) {
+        case ENAMETOOLONG:
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: bad name").arg(function);
+            error = QSharedMemory::KeyError;
+            break;
+        default:
+            setErrorString(function);
+        }
+        return false;
+    }
+
+    // the size may only be set once; ignore errors
+    int ret;
+    EINTR_LOOP(ret, ftruncate(fd, size));
+    if (ret == -1) {
+        setErrorString(QLatin1String("QSharedMemory::create (ftruncate)"));
+        qt_safe_close(fd);
+        return false;
+    }
+
+    qt_safe_close(fd);
+#endif // QT_POSIX_IPC
 
     return true;
 }
 
 bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
 {
+#ifndef QT_POSIX_IPC
     // grab the shared memory segment id
     int id = shmget(unix_key, 0, (mode == QSharedMemory::ReadOnly ? 0444 : 0660));
     if (-1 == id) {
@@ -240,12 +315,55 @@ bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
         setErrorString(QLatin1String("QSharedMemory::attach (shmctl)"));
         return false;
     }
+#else
+    QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+
+    int oflag = (mode == QSharedMemory::ReadOnly ? O_RDONLY : O_RDWR);
+    mode_t omode = (mode == QSharedMemory::ReadOnly ? 0444 : 0660);
+
+    EINTR_LOOP(hand, shm_open(shmName.constData(), oflag, omode));
+    if (hand == -1) {
+        QString function = QLatin1String("QSharedMemory::attach (shm_open)");
+        switch (errno) {
+        case ENAMETOOLONG:
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: bad name").arg(function);
+            error = QSharedMemory::KeyError;
+            break;
+        default:
+            setErrorString(function);
+        }
+        hand = 0;
+        return false;
+    }
+
+    // grab the size
+    QT_STATBUF st;
+    if (QT_FSTAT(hand, &st) == -1) {
+        setErrorString(QLatin1String("QSharedMemory::attach (fstat)"));
+        cleanHandle();
+        return false;
+    }
+    size = st.st_size;
+
+    // grab the memory
+    int mprot = (mode == QSharedMemory::ReadOnly ? PROT_READ : PROT_READ | PROT_WRITE);
+    memory = mmap(0, size, mprot, MAP_SHARED, hand, 0);
+    if (memory == MAP_FAILED || !memory) {
+        setErrorString(QLatin1String("QSharedMemory::attach (mmap)"));
+        cleanHandle();
+        memory = 0;
+        size = 0;
+        return false;
+    }
+#endif // QT_POSIX_IPC
 
     return true;
 }
 
 bool QSharedMemoryPrivate::detach()
 {
+#ifndef QT_POSIX_IPC
     // detach from the memory segment
     if (-1 == shmdt(memory)) {
         QString function = QLatin1String("QSharedMemory::detach");
@@ -292,6 +410,31 @@ bool QSharedMemoryPrivate::detach()
         if (!QFile::remove(nativeKey))
             return false;
     }
+#else
+    // detach from the memory segment
+    if (munmap(memory, size) == -1) {
+        setErrorString(QLatin1String("QSharedMemory::detach (munmap)"));
+        return false;
+    }
+    memory = 0;
+    size = 0;
+
+    // get the number of current attachments
+    int shm_nattch = 0;
+    QT_STATBUF st;
+    if (QT_FSTAT(hand, &st) == 0) {
+        // subtract 2 from linkcount: one for our own open and one for the dir entry
+        shm_nattch = st.st_nlink - 2;
+    }
+    cleanHandle();
+    // if there are no attachments then unlink the shared memory
+    if (shm_nattch == 0) {
+        QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+        if (shm_unlink(shmName.constData()) == -1 && errno != ENOENT)
+            setErrorString(QLatin1String("QSharedMemory::detach (shm_unlink)"));
+    }
+#endif // QT_POSIX_IPC
+
     return true;
 }
 
diff --git a/src/corelib/kernel/qsystemsemaphore.cpp b/src/corelib/kernel/qsystemsemaphore.cpp
index 98ee6f4..ae30348 100644
--- a/src/corelib/kernel/qsystemsemaphore.cpp
+++ b/src/corelib/kernel/qsystemsemaphore.cpp
@@ -151,6 +151,11 @@ QT_BEGIN_NAMESPACE
   creates a new semaphore for that key and sets its resource count to
   \a initialValue.
 
+  In QNX, if the \a mode is \l {QSystemSemaphore::} {Create} and the
+  system already has a semaphore identified by \a key, that semaphore
+  will be deleted and the new one will be created for that key with
+  a resource count set to \a initialValue.
+
   In Windows and in Symbian, \a mode is ignored, and the system always tries to
   create a semaphore for the specified \a key. If the system does not
   already have a semaphore identified as \a key, it creates the
@@ -234,7 +239,7 @@ void QSystemSemaphore::setKey(const QString &key, int initialValue, AccessMode m
         return;
     d->error = NoError;
     d->errorString = QString();
-#if !defined(Q_OS_WIN) && !defined(Q_OS_SYMBIAN)
+#if !defined(Q_OS_WIN) && !defined(Q_OS_SYMBIAN) && !defined(QT_POSIX_IPC)
     // optimization to not destroy/create the file & semaphore
     if (key == d->key && mode == Create && d->createdSemaphore && d->createdFile) {
         d->initialValue = initialValue;
diff --git a/src/corelib/kernel/qsystemsemaphore_p.h b/src/corelib/kernel/qsystemsemaphore_p.h
index 3e5f737..d84d416 100644
--- a/src/corelib/kernel/qsystemsemaphore_p.h
+++ b/src/corelib/kernel/qsystemsemaphore_p.h
@@ -61,6 +61,9 @@
 #ifndef Q_OS_WINCE
 #  include <sys/types.h>
 #endif
+#ifdef QT_POSIX_IPC
+#  include <semaphore.h>
+#endif
 
 #ifdef Q_OS_SYMBIAN
 class RSemaphore;
@@ -84,6 +87,9 @@ public:
 #elif defined(Q_OS_SYMBIAN)
     int handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
     void setErrorString(const QString &function,int err = 0);
+#elif defined(QT_POSIX_IPC)
+    bool handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
+    void setErrorString(const QString &function);
 #else
     key_t handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
     void setErrorString(const QString &function);
@@ -99,6 +105,9 @@ public:
     HANDLE semaphoreLock;
 #elif defined(Q_OS_SYMBIAN)
     RSemaphore semaphore;
+#elif defined(QT_POSIX_IPC)
+    sem_t *semaphore;
+    bool createdSemaphore;
 #else
     key_t unix_key;
     int semaphore;
diff --git a/src/corelib/kernel/qsystemsemaphore_unix.cpp b/src/corelib/kernel/qsystemsemaphore_unix.cpp
index 704afaf..ebf7d6f 100644
--- a/src/corelib/kernel/qsystemsemaphore_unix.cpp
+++ b/src/corelib/kernel/qsystemsemaphore_unix.cpp
@@ -50,7 +50,9 @@
 
 #include <sys/types.h>
 #include <sys/ipc.h>
+#ifndef QT_POSIX_IPC
 #include <sys/sem.h>
+#endif
 #include <fcntl.h>
 #include <errno.h>
 
@@ -67,7 +69,11 @@
 QT_BEGIN_NAMESPACE
 
 QSystemSemaphorePrivate::QSystemSemaphorePrivate() :
+#ifndef QT_POSIX_IPC
     unix_key(-1), semaphore(-1), createdFile(false),
+#else
+    semaphore(SEM_FAILED),
+#endif
     createdSemaphore(false), error(QSystemSemaphore::NoError)
 {
 }
@@ -90,10 +96,18 @@ void QSystemSemaphorePrivate::setErrorString(const QString &function)
         error = QSystemSemaphore::NotFound;
         break;
     case ERANGE:
+    case ENOMEM:
     case ENOSPC:
+    case EMFILE:
+    case ENFILE:
+    case EOVERFLOW:
         errorString = QCoreApplication::translate("QSystemSemaphore", "%1: out of resources").arg(function);
         error = QSystemSemaphore::OutOfResources;
         break;
+    case ENAMETOOLONG:
+        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: name error").arg(function);
+        error = QSystemSemaphore::KeyError;
+        break;
     default:
         errorString = QCoreApplication::translate("QSystemSemaphore", "%1: unknown error %2").arg(function).arg(errno);
         error = QSystemSemaphore::UnknownError;
@@ -109,6 +123,7 @@ void QSystemSemaphorePrivate::setErrorString(const QString &function)
 
     Initialise the semaphore
 */
+#ifndef QT_POSIX_IPC
 key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 {
     if (-1 != unix_key)
@@ -170,6 +185,54 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 
     return unix_key;
 }
+#else
+bool QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
+{
+    if (semaphore != SEM_FAILED)
+        return true;  // we already have a semaphore
+
+    if (fileName.isEmpty()) {
+        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));
+        error = QSystemSemaphore::KeyError;
+        return false;
+    }
+
+    QByteArray semName = QFile::encodeName(fileName);
+
+    // Always try with O_EXCL so we know whether we created the semaphore.
+    int oflag = O_CREAT | O_EXCL;
+    for (int tryNum = 0, maxTries = 1; tryNum < maxTries; ++tryNum) {
+        do {
+            semaphore = sem_open(semName.constData(), oflag, 0666, initialValue);
+        } while (semaphore == SEM_FAILED && errno == EINTR);
+        if (semaphore == SEM_FAILED && errno == EEXIST) {
+            if (mode == QSystemSemaphore::Create) {
+                if (sem_unlink(semName.constData()) == -1 && errno != ENOENT) {
+                    setErrorString(QLatin1String("QSystemSemaphore::handle (sem_unlink)"));
+                    return false;
+                }
+                // Race condition: the semaphore might be recreated before
+                // we call sem_open again, so we'll retry several times.
+                maxTries = 3;
+            } else {
+                // Race condition: if it no longer exists at the next sem_open
+                // call, we won't realise we created it, so we'll leak it later.
+                oflag &= ~O_EXCL;
+                maxTries = 2;
+            }
+        } else {
+            break;
+        }
+    }
+    if (semaphore == SEM_FAILED) {
+        setErrorString(QLatin1String("QSystemSemaphore::handle"));
+        return false;
+    }
+
+    createdSemaphore = (oflag & O_EXCL) != 0;
+    return true;
+}
+#endif // QT_POSIX_IPC
 
 /*!
     \internal
@@ -178,6 +241,7 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 */
 void QSystemSemaphorePrivate::cleanHandle()
 {
+#ifndef QT_POSIX_IPC
     unix_key = -1;
 
     // remove the file if we made it
@@ -198,6 +262,27 @@ void QSystemSemaphorePrivate::cleanHandle()
         }
         createdSemaphore = false;
     }
+#else
+    if (semaphore != SEM_FAILED) {
+        if (sem_close(semaphore) == -1) {
+            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_close)"));
+#ifdef QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_close failed.");
+#endif
+        }
+        semaphore = SEM_FAILED;
+    }
+
+    if (createdSemaphore) {
+        if (sem_unlink(QFile::encodeName(fileName).constData()) == -1 && errno != ENOENT) {
+            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_unlink)"));
+#ifdef QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_unlink failed.");
+#endif
+        }
+        createdSemaphore = false;
+    }
+#endif // QT_POSIX_IPC
 }
 
 /*!
@@ -205,6 +290,7 @@ void QSystemSemaphorePrivate::cleanHandle()
 */
 bool QSystemSemaphorePrivate::modifySemaphore(int count)
 {
+#ifndef QT_POSIX_IPC
     if (-1 == handle())
         return false;
 
@@ -229,6 +315,44 @@ bool QSystemSemaphorePrivate::modifySemaphore(int count)
 #endif
         return false;
     }
+#else
+    if (!handle())
+        return false;
+
+    if (count > 0) {
+        int cnt = count;
+        do {
+            if (sem_post(semaphore) == -1) {
+                setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_post)"));
+#ifdef QSYSTEMSEMAPHORE_DEBUG
+                qDebug() << QLatin1String("QSystemSemaphore::modify sem_post failed") << count << errno;
+#endif
+                // rollback changes to preserve the SysV semaphore behavior
+                for ( ; cnt < count; ++cnt) {
+                    register int res;
+                    EINTR_LOOP(res, sem_wait(semaphore));
+                }
+                return false;
+            }
+            --cnt;
+        } while (cnt > 0);
+    } else {
+        register int res;
+        EINTR_LOOP(res, sem_wait(semaphore));
+        if (res == -1) {
+            // If the semaphore was removed be nice and create it and then modifySemaphore again
+            if (errno == EINVAL || errno == EIDRM) {
+                semaphore = SEM_FAILED;
+                return modifySemaphore(count);
+            }
+            setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_wait)"));
+#ifdef QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::modify sem_wait failed") << count << errno;
+#endif
+            return false;
+        }
+    }
+#endif // QT_POSIX_IPC
 
     return true;
 }