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Change Windows multi-app launch detection.

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Instead of using a .pid file, use a named mutex. This avoids any chance of stale datacausing mis-detection.
This commit is contained in:
James Turner 2017-02-27 15:45:28 +00:00
parent 706ce325d3
commit cad283b2ce
1 changed files with 30 additions and 27 deletions
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43
src/Main/fg_init.cxx
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@ -396,6 +396,26 @@ bool fgInitHome()
return true;
}
bool result = false;
#if defined(SG_WINDOWS)
// don't use a PID file on Windows, because deleting on close is
// unreliable and causes false-positives. Instead, use a named
// mutex.
HANDLE hMutex = CreateMutexA(nullptr, FALSE, "org.flightgear.fgfs.primary");
if (hMutex == nullptr) {
printf("CreateMutex error: %d\n", GetLastError());
SG_LOG(SG_GENERAL, SG_POPUP, "Failed to create mutex for multi-app protection");
return false;
} else if (GetLastError() == ERROR_ALREADY_EXISTS) {
SG_LOG(SG_GENERAL, SG_ALERT, "flightgear instance already running, switching to FG_HOME read-only.");
fgSetBool("/sim/fghome-readonly", true);
return true;
} else {
SG_LOG(SG_GENERAL, SG_INFO, "Created multi-app mutex, we are in writeable mode");
result = true;
}
#else
// write our PID, and check writeability
SGPath pidPath(dataPath, "fgfs.pid");
if (pidPath.exists()) {
@ -407,25 +427,9 @@ bool fgInitHome()
}
char buf[16];
bool result = false;
std::string ps = pidPath.local8BitStr();
#if defined(SG_WINDOWS)
size_t len = snprintf(buf, 16, "%d", _getpid());
HANDLE f = CreateFileA(ps.c_str(), GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ, /* sharing */
NULL, /* security attributes */
CREATE_NEW, /* error if already exists */
FILE_FLAG_DELETE_ON_CLOSE,
NULL /* template */);
result = (f != INVALID_HANDLE_VALUE);
if (result) {
DWORD written;
WriteFile(f, buf, len, &written, NULL /* overlapped */);
}
#else
// POSIX, do open+unlink trick to the file is deleted on exit, even if we
// do open+unlink trick to the file is deleted on exit, even if we
// crash or exit(-1)
ssize_t len = snprintf(buf, 16, "%d", getpid());
int fd = ::open(ps.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_EXCL, 0644);
@ -434,15 +438,14 @@ bool fgInitHome()
if( ::unlink(ps.c_str()) != 0 ) // delete file when app quits
result = false;
}
#endif
fgSetBool("/sim/fghome-readonly", false);
if (!result) {
flightgear::fatalMessageBox("File permissions problem",
"Can't write to user-data storage folder, check file permissions and FG_HOME.",
"User-data at:" + dataPath.utf8Str());
}
#endif
fgSetBool("/sim/fghome-readonly", false);
return result;
}