diff options
Diffstat (limited to 'tdecore/klockfile.cpp')
| -rw-r--r-- | tdecore/klockfile.cpp | 376 |
1 files changed, 376 insertions, 0 deletions
diff --git a/tdecore/klockfile.cpp b/tdecore/klockfile.cpp new file mode 100644 index 000000000..3bd6edb30 --- /dev/null +++ b/tdecore/klockfile.cpp @@ -0,0 +1,376 @@ +/* + This file is part of the KDE libraries + Copyright (c) 2004 Waldo Bastian <bastian@kde.org> + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public + License version 2 as published by the Free Software Foundation. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public License + along with this library; see the file COPYING.LIB. If not, write to + the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, + Boston, MA 02110-1301, USA. +*/ + +#include <klockfile.h> + +#include <config.h> + +#include <sys/types.h> +#ifdef HAVE_SYS_STAT_H +#include <sys/stat.h> +#endif +#ifdef HAVE_SYS_TIME_H +#include <sys/time.h> +#endif +#include <signal.h> +#include <errno.h> +#include <stdlib.h> +#include <unistd.h> + +#include <tqfile.h> +#include <tqtextstream.h> + +#include <kde_file.h> +#include <kapplication.h> +#include <kcmdlineargs.h> +#include <kglobal.h> +#include <ktempfile.h> + +// TODO: http://www.spinnaker.de/linux/nfs-locking.html +// TODO: Make regression test + +class KLockFile::KLockFilePrivate { +public: + TQString file; + int staleTime; + bool isLocked; + bool recoverLock; + bool linkCountSupport; + TQTime staleTimer; + KDE_struct_stat statBuf; + int pid; + TQString hostname; + TQString instance; + TQString lockRecoverFile; +}; + + +// 30 seconds +KLockFile::KLockFile(const TQString &file) +{ + d = new KLockFilePrivate(); + d->file = file; + d->staleTime = 30; + d->isLocked = false; + d->recoverLock = false; + d->linkCountSupport = true; +} + +KLockFile::~KLockFile() +{ + unlock(); + delete d; +} + +int +KLockFile::staleTime() const +{ + return d->staleTime; +} + + +void +KLockFile::setStaleTime(int _staleTime) +{ + d->staleTime = _staleTime; +} + +static bool statResultIsEqual(KDE_struct_stat &st_buf1, KDE_struct_stat &st_buf2) +{ +#define FIELD_EQ(what) (st_buf1.what == st_buf2.what) + return FIELD_EQ(st_dev) && FIELD_EQ(st_ino) && + FIELD_EQ(st_uid) && FIELD_EQ(st_gid) && FIELD_EQ(st_nlink); +#undef FIELD_EQ +} + +static bool testLinkCountSupport(const TQCString &fileName) +{ + KDE_struct_stat st_buf; + // Check if hardlinks raise the link count at all? + ::link( fileName, fileName+".test" ); + int result = KDE_lstat( fileName, &st_buf ); + ::unlink( fileName+".test" ); + return ((result == 0) && (st_buf.st_nlink == 2)); +} + +static KLockFile::LockResult lockFile(const TQString &lockFile, KDE_struct_stat &st_buf, bool &linkCountSupport) +{ + TQCString lockFileName = TQFile::encodeName( lockFile ); + int result = KDE_lstat( lockFileName, &st_buf ); + if (result == 0) + return KLockFile::LockFail; + + KTempFile uniqueFile(lockFile, TQString::null, 0644); + uniqueFile.setAutoDelete(true); + if (uniqueFile.status() != 0) + return KLockFile::LockError; + + char hostname[256]; + hostname[0] = 0; + gethostname(hostname, 255); + hostname[255] = 0; + TQCString instanceName = KCmdLineArgs::appName(); + + (*(uniqueFile.textStream())) << TQString::number(getpid()) << endl + << instanceName << endl + << hostname << endl; + uniqueFile.close(); + + TQCString uniqueName = TQFile::encodeName( uniqueFile.name() ); + +#ifdef Q_OS_UNIX + // Create lock file + result = ::link( uniqueName, lockFileName ); + if (result != 0) + return KLockFile::LockError; + + if (!linkCountSupport) + return KLockFile::LockOK; +#else + //TODO for win32 + return KLockFile::LockOK; +#endif + + KDE_struct_stat st_buf2; + result = KDE_lstat( uniqueName, &st_buf2 ); + if (result != 0) + return KLockFile::LockError; + + result = KDE_lstat( lockFileName, &st_buf ); + if (result != 0) + return KLockFile::LockError; + + if (!statResultIsEqual(st_buf, st_buf2) || S_ISLNK(st_buf.st_mode) || S_ISLNK(st_buf2.st_mode)) + { + // SMBFS supports hardlinks by copying the file, as a result the above test will always fail + if ((st_buf.st_nlink == 1) && (st_buf2.st_nlink == 1) && (st_buf.st_ino != st_buf2.st_ino)) + { + linkCountSupport = testLinkCountSupport(uniqueName); + if (!linkCountSupport) + return KLockFile::LockOK; // Link count support is missing... assume everything is OK. + } + return KLockFile::LockFail; + } + + return KLockFile::LockOK; +} + +static KLockFile::LockResult deleteStaleLock(const TQString &lockFile, KDE_struct_stat &st_buf, bool &linkCountSupport) +{ + // This is dangerous, we could be deleting a new lock instead of + // the old stale one, let's be very careful + + // Create temp file + KTempFile ktmpFile(lockFile); + if (ktmpFile.status() != 0) + return KLockFile::LockError; + + TQCString lckFile = TQFile::encodeName(lockFile); + TQCString tmpFile = TQFile::encodeName(ktmpFile.name()); + ktmpFile.close(); + ktmpFile.unlink(); + +#ifdef Q_OS_UNIX + // link to lock file + if (::link(lckFile, tmpFile) != 0) + return KLockFile::LockFail; // Try again later +#else + //TODO for win32 + return KLockFile::LockOK; +#endif + + // check if link count increased with exactly one + // and if the lock file still matches + KDE_struct_stat st_buf1; + KDE_struct_stat st_buf2; + memcpy(&st_buf1, &st_buf, sizeof(KDE_struct_stat)); + st_buf1.st_nlink++; + if ((KDE_lstat(tmpFile, &st_buf2) == 0) && statResultIsEqual(st_buf1, st_buf2)) + { + if ((KDE_lstat(lckFile, &st_buf2) == 0) && statResultIsEqual(st_buf1, st_buf2)) + { + // - - if yes, delete lock file, delete temp file, retry lock + qWarning("WARNING: deleting stale lockfile %s", lckFile.data()); + ::unlink(lckFile); + ::unlink(tmpFile); + return KLockFile::LockOK; + } + } + + // SMBFS supports hardlinks by copying the file, as a result the above test will always fail + if (linkCountSupport) + { + linkCountSupport = testLinkCountSupport(tmpFile); + } + + if (!linkCountSupport && + (KDE_lstat(lckFile, &st_buf2) == 0) && + statResultIsEqual(st_buf, st_buf2)) + { + // Without support for link counts we will have a little race condition + qWarning("WARNING: deleting stale lockfile %s", lckFile.data()); + ::unlink(lckFile); + ::unlink(tmpFile); + return KLockFile::LockOK; + } + + // Failed to delete stale lock file + qWarning("WARNING: Problem deleting stale lockfile %s", lckFile.data()); + ::unlink(tmpFile); + return KLockFile::LockFail; +} + + +KLockFile::LockResult KLockFile::lock(int options) +{ + if (d->isLocked) + return KLockFile::LockOK; + + KLockFile::LockResult result; + int hardErrors = 5; + int n = 5; + while(true) + { + KDE_struct_stat st_buf; + result = lockFile(d->file, st_buf, d->linkCountSupport); + if (result == KLockFile::LockOK) + { + d->staleTimer = TQTime(); + break; + } + else if (result == KLockFile::LockError) + { + d->staleTimer = TQTime(); + if (--hardErrors == 0) + { + break; + } + } + else // KLockFile::Fail + { + if (!d->staleTimer.isNull() && !statResultIsEqual(d->statBuf, st_buf)) + d->staleTimer = TQTime(); + + if (!d->staleTimer.isNull()) + { + bool isStale = false; + if ((d->pid > 0) && !d->hostname.isEmpty()) + { + // Check if hostname is us + char hostname[256]; + hostname[0] = 0; + gethostname(hostname, 255); + hostname[255] = 0; + + if (d->hostname == hostname) + { + // Check if pid still exists + int res = ::kill(d->pid, 0); + if ((res == -1) && (errno == ESRCH)) + isStale = true; + } + } + if (d->staleTimer.elapsed() > (d->staleTime*1000)) + isStale = true; + + if (isStale) + { + if ((options & LockForce) == 0) + return KLockFile::LockStale; + + result = deleteStaleLock(d->file, d->statBuf, d->linkCountSupport); + + if (result == KLockFile::LockOK) + { + // Lock deletion successful + d->staleTimer = TQTime(); + continue; // Now try to get the new lock + } + else if (result != KLockFile::LockFail) + { + return result; + } + } + } + else + { + memcpy(&(d->statBuf), &st_buf, sizeof(KDE_struct_stat)); + d->staleTimer.start(); + + d->pid = -1; + d->hostname = TQString::null; + d->instance = TQString::null; + + TQFile file(d->file); + if (file.open(IO_ReadOnly)) + { + TQTextStream ts(&file); + if (!ts.atEnd()) + d->pid = ts.readLine().toInt(); + if (!ts.atEnd()) + d->instance = ts.readLine(); + if (!ts.atEnd()) + d->hostname = ts.readLine(); + } + } + } + + if ((options & LockNoBlock) != 0) + break; + + struct timeval tv; + tv.tv_sec = 0; + tv.tv_usec = n*((KApplication::random() % 200)+100); + if (n < 2000) + n = n * 2; + +#ifdef Q_OS_UNIX + select(0, 0, 0, 0, &tv); +#else + //TODO for win32 +#endif + } + if (result == LockOK) + d->isLocked = true; + return result; +} + +bool KLockFile::isLocked() const +{ + return d->isLocked; +} + +void KLockFile::unlock() +{ + if (d->isLocked) + { + ::unlink(TQFile::encodeName(d->file)); + d->isLocked = false; + } +} + +bool KLockFile::getLockInfo(int &pid, TQString &hostname, TQString &appname) +{ + if (d->pid == -1) + return false; + pid = d->pid; + hostname = d->hostname; + appname = d->instance; + return true; +} |