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Improved creating/attaching shared memory: there is a possibility of a stale shared memory

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under /tmp.
This commit is contained in:
Gerhard Hoffmann 2024-02-02 13:32:56 +01:00
parent 3bf3e741a0
commit fc28666946
1 changed files with 109 additions and 5 deletions
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114
src/shared_mem_buffer.cpp
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@ -1,7 +1,13 @@
#include "shared_mem_buffer.h"
#include <QDebug>
#include <QFile>
#include <QString>
#include <QTextStream>
#include <QDateTime>
#include <QCoreApplication>
#include <atomic>
#include <algorithm>
#ifdef QT_POSIX_IPC
// The POSIX backend can be explicitly selected using the -feature-ipc_posix
@ -9,33 +15,124 @@
// macro will be defined. -> we use SystemV shared memory
#error "QT_POSIX_IPC defined"
#else
#ifdef __linux__
#ifdef linux
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h> // ftok
#endif
#endif
//static bool shdMemFirstUse;
static QString read1stLineOfFile(QString fileName) { // read for instance /etc/os-release
QFile f(fileName);
if (f.exists()) {
if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
QTextStream in(&f);
in.setCodec("UTF-8");
while(!in.atEnd()) {
return in.readLine();
}
}
}
return "N/A";
}
//QSharedMemory *SharedMemBuffer::getShm(std::size_t size) {
QSharedMemory *SharedMem::getShm(std::size_t size) {
static QSharedMemory shMem;
if (size > 0) {
#ifdef __linux__
//static const long nativeKey = ftok("/etc/os-release", 'H');
//static const QString fkey = std::to_string(nativeKey).c_str();
static const QString fkey = "0123456?000=7";
#ifdef linux
static const long nativeKey = ftok("/etc/os-release", 'H');
static const QString fkey = std::to_string(nativeKey).c_str();
//static const QString fkey = "0123456?000=7";
#else
static const QString fkey = "0123456?000=9";
#endif
qCritical() << __func__ << ":" << __LINE__ << ": size" << size;
shMem.setKey(fkey);
if (!shMem.isAttached()) {
if (shMem.create(size)) {
qCritical() << __func__ << ":" << __LINE__ << ": created shared memory";
#ifdef linux
if ((size != (std::size_t)shMem.size()) || (sizeof(SharedMem) != shMem.size())) {
qCritical() << __func__ << ":" << __LINE__
<< "size=" << size
<< "shMem.size=" << shMem.size()
<< "sizeof(SharedMem)=" << sizeof(SharedMem)
<< "ABOUT TO REBOOT SYSTEM...";
if (system("reboot")) {
// reboot system -> shared memory re-created
}
}
struct SharedMem *sh = (SharedMem *)(shMem.data());
memset(sh->indat_HWversion, 0x00, sizeof(sh->indat_HWversion));
memset(sh->indat_SWversion, 0x00, sizeof(sh->indat_SWversion));
memset(sh->os_release, 0x00, sizeof(sh->os_release));
memset(sh->date_of_creation, 0x00, sizeof(sh->date_of_creation));
memset(sh->creator, 0x00, sizeof(sh->creator));
QString const &os_release = read1stLineOfFile("/etc/os-release");
strncpy(sh->os_release, os_release.toStdString().c_str(),
std::min((int)os_release.size(), (int)sizeof(sh->os_release)-1));
QString const &currentDateTime = QDateTime::currentDateTime().toString(Qt::ISODate);
char const *current = currentDateTime.toUtf8().constData();
strncpy(sh->date_of_creation, current,
std::min((int)strlen(current), (int)sizeof(sh->date_of_creation)-1));
QString const &appPid = QString("%1 (%2)").arg(QCoreApplication::applicationName())
.arg(QCoreApplication::applicationPid());
strncpy(sh->creator, appPid.toStdString().c_str(),
std::min((int)strlen(appPid.toStdString().c_str()),
(int)sizeof(sh->creator)-1));
qCritical() << "os-release:" << sh->os_release;
qCritical() << " creator:" << sh->creator;
qCritical() << " date:" << sh->date_of_creation;
#else
Q_ASSERT_X(size != shMem.size(), "compare sizes", "sizes different");
Q_ASSERT_X(sizeof(SharedMem) != shMem.size(), "compare sizes", "sizes different");
#endif
return &shMem;
} else {
if (shMem.error() == QSharedMemory::AlreadyExists) {
if (shMem.attach()) {
#ifdef linux
if ((size != (std::size_t)shMem.size()) || (sizeof(SharedMem) != shMem.size())) {
qCritical() << __func__ << ":" << __LINE__
<< "size=" << size
<< "shMem.size=" << shMem.size()
<< "sizeof(SharedMem)=" << sizeof(SharedMem)
<< "ABOUT TO REBOOT SYSTEM...";
if (system("reboot")) {
// reboot system -> shared memory re-created
}
}
#else
Q_ASSERT_X(size != shMem.size(), "compare sizes", "sizes different");
Q_ASSERT_X(sizeof(SharedMem) != shMem.size(), "compare sizes", "sizes different");
#endif
QString const &appPid = QString("%1 (%2)").arg(QCoreApplication::applicationName())
.arg(QCoreApplication::applicationPid());
qCritical() << __func__ << ":" << __LINE__ << appPid << "attached shared memory";
struct SharedMem const *sh = (SharedMem const *)(shMem.data());
qCritical() << "os-release:" << sh->os_release;
qCritical() << " creator:" << sh->creator;
qCritical() << " date:" << sh->date_of_creation;
return &shMem;
}
}
@ -43,6 +140,13 @@ QSharedMemory *SharedMem::getShm(std::size_t size) {
qCritical() << shMem.nativeKey() << shMem.key() << shMem.data()
<< shMem.error() << shMem.errorString();
return nullptr;
} else {
qCritical() << __func__ << ":" << __LINE__ << "shared memory already attached";
struct SharedMem const *sh = (SharedMem const *)(shMem.data());
qCritical() << "os-release:" << sh->os_release;
qCritical() << " creator:" << sh->creator;
qCritical() << " date:" << sh->date_of_creation;
}
}
return &shMem;