/*
** 2004 May 22
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific to Unix systems.
*/
#include "sqliteInt.h"
#include "os.h"
#if OS_UNIX /* This file is used on unix only */
/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it. If the OS lacks
** large file support, these should be no-ops.
**
** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
** on the compiler command line. This is necessary if you are compiling
** on a recent machine (ex: RedHat 7.2) but you want your code to work
** on an older machine (ex: RedHat 6.0). If you compile on RedHat 7.2
** without this option, LFS is enable. But LFS does not exist in the kernel
** in RedHat 6.0, so the code won't work. Hence, for maximum binary
** portability you should omit LFS.
*/
#ifndef SQLITE_DISABLE_LFS
# define _LARGE_FILE 1
# ifndef _FILE_OFFSET_BITS
# define _FILE_OFFSET_BITS 64
# endif
# define _LARGEFILE_SOURCE 1
#endif
/*
** standard include files.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
/*
** If we are to be thread-safe, include the pthreads header and define
** the SQLITE_UNIX_THREADS macro.
*/
#if defined(THREADSAFE) && THREADSAFE
# include <pthread.h>
# define SQLITE_UNIX_THREADS 1
#endif
/*
** Default permissions when creating a new file
*/
#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
#endif
/*
** The unixFile structure is subclass of OsFile specific for the unix
** protability layer.
*/
typedef struct unixFile unixFile;
struct unixFile {
IoMethod const *pMethod; /* Always the first entry */
struct openCnt *pOpen; /* Info about all open fd's on this inode */
struct lockInfo *pLock; /* Info about locks on this inode */
int h; /* The file descriptor */
unsigned char locktype; /* The type of lock held on this fd */
unsigned char isOpen; /* True if needs to be closed */
unsigned char fullSync; /* Use F_FULLSYNC if available */
int dirfd; /* File descriptor for the directory */
i64 offset; /* Seek offset */
#ifdef SQLITE_UNIX_THREADS
pthread_t tid; /* The thread that "owns" this OsFile */
#endif
};
/*
** Provide the ability to override some OS-layer functions during
** testing. This is used to simulate OS crashes to verify that
** commits are atomic even in the event of an OS crash.
*/
#ifdef SQLITE_CRASH_TEST
extern int sqlite3CrashTestEnable;
extern int sqlite3CrashOpenReadWrite(const char*, OsFile**, int*);
extern int sqlite3CrashOpenExclusive(const char*, OsFile**, int);
extern int sqlite3CrashOpenReadOnly(const char*, OsFile**, int);
# define CRASH_TEST_OVERRIDE(X,A,B,C) \
if(sqlite3CrashTestEnable){ return X(A,B,C); }
#else
# define CRASH_TEST_OVERRIDE(X,A,B,C) /* no-op */
#endif
/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"
/*
** Do not include any of the File I/O interface procedures if the
** SQLITE_OMIT_DISKIO macro is defined (indicating that the database
** will be in-memory only)
*/
#ifndef SQLITE_OMIT_DISKIO
/*
** Define various macros that are missing from some systems.
*/
#ifndef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifdef SQLITE_DISABLE_LFS
# undef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
#ifndef O_BINARY
# define O_BINARY 0
#endif
/*
** The DJGPP compiler environment looks mostly like Unix, but it
** lacks the fcntl() system call. So redefine fcntl() to be something
** that always succeeds. This means that locking does not occur under
** DJGPP. But it's DOS - what did you expect?
*/
#ifdef __DJGPP__
# define fcntl(A,B,C) 0
#endif
/*
** The threadid macro resolves to the thread-id or to 0. Used for
** testing and debugging only.
*/
#ifdef SQLITE_UNIX_THREADS
#define threadid pthread_self()
#else
#define threadid 0
#endif
/*
** Set or check the OsFile.tid field. This field is set when an OsFile
** is first opened. All subsequent uses of the OsFile verify that the
** same thread is operating on the OsFile. Some operating systems do
** not allow locks to be overridden by other threads and that restriction
** means that sqlite3* database handles cannot be moved from one thread
** to another. This logic makes sure a user does not try to do that
** by mistake.
**
** Version 3.3.1 (2006-01-15): OsFiles can be moved from one thread to
** another as long as we are running on a system that supports threads
** overriding each others locks (which now the most common behavior)
** or if no locks are held. But the OsFile.pLock field needs to be
** recomputed because its key includes the thread-id. See the
** transferOwnership() function below for additional information
*/
#if defined(SQLITE_UNIX_THREADS)
# define SET_THREADID(X) (X)->tid = pthread_self()
# define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \
!pthread_equal((X)->tid, pthread_self()))
#else
# define SET_THREADID(X)
# define CHECK_THREADID(X) 0
#endif
/*
** Here is the dirt on POSIX advisory locks: ANSI STD 1003.1 (1996)
** section 6.5.2.2 lines 483 through 490 specify that when a process
** sets or clears a lock, that operation overrides any prior locks set
** by the same process. It does not explicitly say so, but this implies
** that it overrides locks set by the same process using a different
** file descriptor. Consider this test case:
**
** int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
** int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
**
** Suppose ./file1 and ./file2 are really the same file (because
** one is a hard or symbolic link to the other) then if you set
** an exclusive lock on fd1, then try to get an exclusive lock
** on fd2, it works. I would have expected the second lock to
** fail since there was already a lock on the file due to fd1.
** But not so. Since both locks came from the same process, the
** second overrides the first, even though they were on different
** file descriptors opened on different file names.
**
** Bummer. If you ask me, this is broken. Badly broken. It means
** that we cannot use POSIX locks to synchronize file access among
** competing threads of the same process. POSIX locks will work fine
** to synchronize access for threads in separate processes, but not
** threads within the same process.
**
** To work around the problem, SQLite has to manage file locks internally
** on its own. Whenever a new database is opened, we have to find the
** specific inode of the database file (the inode is determined by the
** st_dev and st_ino fields of the stat structure that fstat() fills in)
** and check for locks already existing on that inode. When locks are
** created or removed, we have to look at our own internal record of the
** locks to see if another thread has previously set a lock on that same
** inode.
**
** The OsFile structure for POSIX is no longer just an integer file
** descriptor. It is now a structure that holds the integer file
** descriptor and a pointer to a structure that describes the internal
** locks on the corresponding inode. There is one locking structure
** per inode, so if the same inode is opened twice, both OsFile structures
** point to the same locking structure. The locking structure keeps
** a reference count (so we will know when to delete it) and a "cnt"
** field that tells us its internal lock status. cnt==0 means the
** file is unlocked. cnt==-1 means the file has an exclusive lock.
** cnt>0 means there are cnt shared locks on the file.
**
** Any attempt to lock or unlock a file first checks the locking
** structure. The fcntl() system call is only invoked to set a
** POSIX lock if the internal lock structure transitions between
** a locked and an unlocked state.
**
** 2004-Jan-11:
** More recent discoveries about POSIX advisory locks. (The more
** I discover, the more I realize the a POSIX advisory locks are
** an abomination.)
**
** If you close a file descriptor that points to a file that has locks,
** all locks on that file that are owned by the current process are
** released. To work around this problem, each OsFile structure contains
** a pointer to an openCnt structure. There is one openCnt structure
** per open inode, which means that multiple OsFiles can point to a single
** openCnt. When an attempt is made to close an OsFile, if there are
** other OsFiles open on the same inode that are holding locks, the call
** to close() the file descriptor is deferred until all of the locks clear.
** The openCnt structure keeps a list of file descriptors that need to
** be closed and that list is walked (and cleared) when the last lock
** clears.
**
** First, under Linux threads, because each thread has a separate
** process ID, lock operations in one thread do not override locks
** to the same file in other threads. Linux threads behave like
** separate processes in this respect. But, if you close a file
** descriptor in linux threads, all locks are cleared, even locks
** on other threads and even though the other threads have different
** process IDs. Linux threads is inconsistent in this respect.
** (I'm beginning to think that linux threads is an abomination too.)
** The consequence of this all is that the hash table for the lockInfo
** structure has to include the process id as part of its key because
** locks in different threads are treated as distinct. But the
** openCnt structure should not include the process id in its
** key because close() clears lock on all threads, not just the current
** thread. Were it not for this goofiness in linux threads, we could
** combine the lockInfo and openCnt structures into a single structure.
**
** 2004-Jun-28:
** On some versions of linux, threads can override each others locks.
** On others not. Sometimes you can change the behavior on the same
** system by setting the LD_ASSUME_KERNEL environment variable. The
** POSIX standard is silent as to which behavior is correct, as far
** as I can tell, so other versions of unix might show the same
** inconsistency. There is no little doubt in my mind that posix
** advisory locks and linux threads are profoundly broken.
**
** To work around the inconsistencies, we have to test at runtime
** whether or not threads can override each others locks. This test
** is run once, the first time any lock is attempted. A static
** variable is set to record the results of this test for future
** use.
*/
/*
** An instance of the following structure serves as the key used
** to locate a particular lockInfo structure given its inode.
**
** If threads cannot override each others locks, then we set the
** lockKey.tid field to the thread ID. If threads can override
** each others locks then tid is always set to zero. tid is omitted
** if we compile without threading support.
*/
struct lockKey {
dev_t dev; /* Device number */
ino_t ino; /* Inode number */
#ifdef SQLITE_UNIX_THREADS
pthread_t tid; /* Thread ID or zero if threads can override each other */
#endif
};
/*
** An instance of the following structure is allocated for each open
** inode on each thread with a different process ID. (Threads have
** different process IDs on linux, but not on most other unixes.)
**
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
struct lockKey key; /* The lookup key */
int cnt; /* Number of SHARED locks held */
int locktype; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
int nRef; /* Number of pointers to this structure */
};
/*
** An instance of the following structure serves as the key used
** to locate a particular openCnt structure given its inode. This
** is the same as the lockKey except that the thread ID is omitted.
*/
struct openKey {
dev_t dev; /* Device number */
ino_t ino; /* Inode number */
};
/*
** An instance of the following structure is allocated for each open
** inode. This structure keeps track of the number of locks on that
** inode. If a close is attempted against an inode that is holding
** locks, the close is deferred until all locks clear by adding the
** file descriptor to be closed to the pending list.
*/
struct openCnt {
struct openKey key; /* The lookup key */
int nRef; /* Number of pointers to this structure */
int nLock; /* Number of outstanding locks */
int nPending; /* Number of pending close() operations */
int *aPending; /* Malloced space holding fd's awaiting a close() */
};
/*
** These hash tables map inodes and file descriptors (really, lockKey and
** openKey structures) into lockInfo and openCnt structures. Access to
** these hash tables must be protected by a mutex.
*/
static Hash lockHash = {SQLITE_HASH_BINARY, 0, 0, 0,
sqlite3ThreadSafeMalloc, sqlite3ThreadSafeFree, 0, 0};
static Hash openHash = {SQLITE_HASH_BINARY, 0, 0, 0,
sqlite3ThreadSafeMalloc, sqlite3ThreadSafeFree, 0, 0};
#ifdef SQLITE_UNIX_THREADS
/*
** This variable records whether or not threads can override each others
** locks.
**
** 0: No. Threads cannot override each others locks.
** 1: Yes. Threads can override each others locks.
** -1: We don't know yet.
**
** On some systems, we know at compile-time if threads can override each
** others locks. On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro
** will be set appropriately. On other systems, we have to check at
** runtime. On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is
** undefined.
**
** This variable normally has file scope only. But during testing, we make
** it a global so that the test code can change its value in order to verify
** that the right stuff happens in either case.
*/
#ifndef SQLITE_THREAD_OVERRIDE_LOCK
# define SQLITE_THREAD_OVERRIDE_LOCK -1
#endif
#ifdef SQLITE_TEST
int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
#else
static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
#endif
/*
** This structure holds information passed into individual test
** threads by the testThreadLockingBehavior() routine.
*/
struct threadTestData {
int fd; /* File to be locked */
struct flock lock; /* The locking operation */
int result; /* Result of the locking operation */
};
#ifdef SQLITE_LOCK_TRACE
/*
** Print out information about all locking operations.
**
** This routine is used for troubleshooting locks on multithreaded
** platforms. Enable by compiling with the -DSQLITE_LOCK_TRACE
** command-line option on the compiler. This code is normally
** turned off.
*/
static int lockTrace(int fd, int op, struct flock *p){
char *zOpName, *zType;
int s;
int savedErrno;
if( op==F_GETLK ){
zOpName = "GETLK";
}else if( op==F_SETLK ){
zOpName = "SETLK";
}else{
s = fcntl(fd, op, p);
sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
return s;
}
if( p->l_type==F_RDLCK ){
zType = "RDLCK";
}else if( p->l_type==F_WRLCK ){
zType = "WRLCK";
}else if( p->l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
assert( p->l_whence==SEEK_SET );
s = fcntl(fd, op, p);
savedErrno = errno;
sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
(int)p->l_pid, s);
if( s && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
struct flock l2;
l2 = *p;
fcntl(fd, F_GETLK, &l2);
if( l2.l_type==F_RDLCK ){
zType = "RDLCK";
}else if( l2.l_type==F_WRLCK ){
zType = "WRLCK";
}else if( l2.l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
}
errno = savedErrno;
return s;
}
#define fcntl lockTrace
#endif /* SQLITE_LOCK_TRACE */
/*
** The testThreadLockingBehavior() routine launches two separate
** threads on this routine. This routine attempts to lock a file
** descriptor then returns. The success or failure of that attempt
** allows the testThreadLockingBehavior() procedure to determine
** whether or not threads can override each others locks.
*/
static void *threadLockingTest(void *pArg){
struct threadTestData *pData = (struct threadTestData*)pArg;
pData->result = fcntl(pData->fd, F_SETLK, &pData->lock);
return pArg;
}
/*
** This procedure attempts to determine whether or not threads
** can override each others locks then sets the
** threadsOverrideEachOthersLocks variable appropriately.
*/
static void testThreadLockingBehavior(int fd_orig){
int fd;
struct threadTestData d[2];
pthread_t t[2];
fd = dup(fd_orig);
if( fd<0 ) return;
memset(d, 0, sizeof(d));
d[0].fd = fd;
d[0].lock.l_type = F_RDLCK;
d[0].lock.l_len = 1;
d[0].lock.l_start = 0;
d[0].lock.l_whence = SEEK_SET;
d[1] = d[0];
d[1].lock.l_type = F_WRLCK;
pthread_create(&t[0], 0, threadLockingTest, &d[0]);
pthread_create(&t[1], 0, threadLockingTest, &d[1]);
pthread_join(t[0], 0);
pthread_join(t[1], 0);
close(fd);
threadsOverrideEachOthersLocks = d[0].result==0 && d[1].result==0;
}
#endif /* SQLITE_UNIX_THREADS */
/*
** Release a lockInfo structure previously allocated by findLockInfo().
*/
static void releaseLockInfo(struct lockInfo *pLock){
assert( sqlite3OsInMutex(1) );
pLock->nRef--;
if( pLock->nRef==0 ){
sqlite3HashInsert(&lockHash, &pLock->key, sizeof(pLock->key), 0);
sqlite3ThreadSafeFree(pLock);
}
}
/*
** Release a openCnt structure previously allocated by findLockInfo().
*/
static void releaseOpenCnt(struct openCnt *pOpen){
assert( sqlite3OsInMutex(1) );
pOpen->nRef--;
if( pOpen->nRef==0 ){
sqlite3HashInsert(&openHash, &pOpen->key, sizeof(pOpen->key), 0);
free(pOpen->aPending);
sqlite3ThreadSafeFree(pOpen);
}
}
/*
** Given a file descriptor, locate lockInfo and openCnt structures that
** describes that file descriptor. Create new ones if necessary. The
** return values might be uninitialized if an error occurs.
**
** Return the number of errors.
*/
static int findLockInfo(
int fd, /* The file descriptor used in the key */
struct lockInfo **ppLock, /* Return the lockInfo structure here */
struct openCnt **ppOpen /* Return the openCnt structure here */
){
int rc;
struct lockKey key1;
struct openKey key2;
struct stat statbuf;
struct lockInfo *pLock;
struct openCnt *pOpen;
rc = fstat(fd, &statbuf);
if( rc!=0 ) return 1;
assert( sqlite3OsInMutex(1) );
memset(&key1, 0, sizeof(key1));
key1.dev = statbuf.st_dev;
key1.ino = statbuf.st_ino;
#ifdef SQLITE_UNIX_THREADS
if( threadsOverrideEachOthersLocks<0 ){
testThreadLockingBehavior(fd);
}
key1.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
#endif
memset(&key2, 0, sizeof(key2));
key2.dev = statbuf.st_dev;
key2.ino = statbuf.st_ino;
pLock = (struct lockInfo*)sqlite3HashFind(&lockHash, &key1, sizeof(key1));
if( pLock==0 ){
struct lockInfo *pOld;
pLock = sqlite3ThreadSafeMalloc( sizeof(*pLock) );
if( pLock==0 ){
rc = 1;
goto exit_findlockinfo;
}
pLock->key = key1;
pLock->nRef = 1;
pLock->cnt = 0;
pLock->locktype = 0;
pOld = sqlite3HashInsert(&lockHash, &pLock->key, sizeof(key1), pLock);
if( pOld!=0 ){
assert( pOld==pLock );
sqlite3ThreadSafeFree(pLock);
rc = 1;
goto exit_findlockinfo;
}
}else{
pLock->nRef++;
}
*ppLock = pLock;
if( ppOpen!=0 ){
pOpen = (struct openCnt*)sqlite3HashFind(&openHash, &key2, sizeof(key2));
if( pOpen==0 ){
struct openCnt *pOld;
pOpen = sqlite3ThreadSafeMalloc( sizeof(*pOpen) );
if( pOpen==0 ){
releaseLockInfo(pLock);
rc = 1;
goto exit_findlockinfo;
}
pOpen->key = key2;
pOpen->nRef = 1;
pOpen->nLock = 0;
pOpen->nPending = 0;
pOpen->aPending = 0;
pOld = sqlite3HashInsert(&openHash, &pOpen->key, sizeof(key2), pOpen);
if( pOld!=0 ){
assert( pOld==pOpen );
sqlite3ThreadSafeFree(pOpen);
releaseLockInfo(pLock);
rc = 1;
goto exit_findlockinfo;
}
}else{
pOpen->nRef++;
}
*ppOpen = pOpen;
}
exit_findlockinfo:
return rc;
}
#ifdef SQLITE_DEBUG
/*
** Helper function for printing out trace information from debugging
** binaries. This returns the string represetation of the supplied
** integer lock-type.
*/
static const char *locktypeName(int locktype){
switch( locktype ){
case NO_LOCK: return "NONE";
case SHARED_LOCK: return "SHARED";
case RESERVED_LOCK: return "RESERVED";
case PENDING_LOCK: return "PENDING";
case EXCLUSIVE_LOCK: return "EXCLUSIVE";
}
return "ERROR";
}
#endif
/*
** If we are currently in a different thread than the thread that the
** unixFile argument belongs to, then transfer ownership of the unixFile
** over to the current thread.
**
** A unixFile is only owned by a thread on systems where one thread is
** unable to override locks created by a different thread. RedHat9 is
** an example of such a system.
**
** Ownership transfer is only allowed if the unixFile is currently unlocked.
** If the unixFile is locked and an ownership is wrong, then return
** SQLITE_MISUSE. SQLITE_OK is returned if everything works.
*/
#ifdef SQLITE_UNIX_THREADS
static int transferOwnership(unixFile *pFile){
int rc;
pthread_t hSelf;
if( threadsOverrideEachOthersLocks ){
/* Ownership transfers not needed on this system */
return SQLITE_OK;
}
hSelf = pthread_self();
if( pthread_equal(pFile->tid, hSelf) ){
/* We are still in the same thread */
TRACE1("No-transfer, same thread\n");
return SQLITE_OK;
}
if( pFile->locktype!=NO_LOCK ){
/* We cannot change ownership while we are holding a lock! */
return SQLITE_MISUSE;
}
TRACE4("Transfer ownership of %d from %d to %d\n", pFile->h,pFile->tid,hSelf);
pFile->tid = hSelf;
releaseLockInfo(pFile->pLock);
rc = findLockInfo(pFile->h, &pFile->pLock, 0);
TRACE5("LOCK %d is now %s(%s,%d)\n", pFile->h,
locktypeName(pFile->locktype),
locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);
return rc;
}
#else
/* On single-threaded builds, ownership transfer is a no-op */
# define transferOwnership(X) SQLITE_OK
#endif
/*
** Delete the named file
*/
int sqlite3UnixDelete(const char *zFilename){
unlink(zFilename);
return SQLITE_OK;
}
/*
** Return TRUE if the named file exists.
*/
int sqlite3UnixFileExists(const char *zFilename){
return access(zFilename, 0)==0;
}
/* Forward declaration */
static int allocateUnixFile(unixFile *pInit, OsFile **pId);
/*
** Attempt to open a file for both reading and writing. If that
** fails, try opening it read-only. If the file does not exist,
** try to create it.
**
** On success, a handle for the open file is written to *id
** and *pReadonly is set to 0 if the file was opened for reading and
** writing or 1 if the file was opened read-only. The function returns
** SQLITE_OK.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id and *pReadonly unchanged.
*/
int sqlite3UnixOpenReadWrite(
const char *zFilename,
OsFile **pId,
int *pReadonly
){
int rc;
unixFile f;
CRASH_TEST_OVERRIDE(sqlite3CrashOpenReadWrite, zFilename, pId, pReadonly);
assert( 0==*pId );
f.h = open(zFilename, O_RDWR|O_CREAT|O_LARGEFILE|O_BINARY,
SQLITE_DEFAULT_FILE_PERMISSIONS);
if( f.h<0 ){
#ifdef EISDIR
if( errno==EISDIR ){
return SQLITE_CANTOPEN;
}
#endif
f.h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY);
if( f.h<0 ){
return SQLITE_CANTOPEN;
}
*pReadonly = 1;
}else{
*pReadonly = 0;
}
sqlite3OsEnterMutex();
rc = findLockInfo(f.h, &f.pLock, &f.pOpen);
sqlite3OsLeaveMutex();
if( rc ){
close(f.h);
return SQLITE_NOMEM;
}
TRACE3("OPEN %-3d %s\n", f.h, zFilename);
return allocateUnixFile(&f, pId);
}
/*
** Attempt to open a new file for exclusive access by this process.
** The file will be opened for both reading and writing. To avoid
** a potential security problem, we do not allow the file to have
** previously existed. Nor do we allow the file to be a symbolic
** link.
**
** If delFlag is true, then make arrangements to automatically delete
** the file when it is closed.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqlite3UnixOpenExclusive(const char *zFilename, OsFile **pId, int delFlag){
int rc;
unixFile f;
CRASH_TEST_OVERRIDE(sqlite3CrashOpenExclusive, zFilename, pId, delFlag);
assert( 0==*pId );
f.h = open(zFilename,
O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW|O_LARGEFILE|O_BINARY,
SQLITE_DEFAULT_FILE_PERMISSIONS);
if( f.h<0 ){
return SQLITE_CANTOPEN;
}
sqlite3OsEnterMutex();
rc = findLockInfo(f.h, &f.pLock, &f.pOpen);
sqlite3OsLeaveMutex();
if( rc ){
close(f.h);
unlink(zFilename);
return SQLITE_NOMEM;
}
if( delFlag ){
unlink(zFilename);
}
TRACE3("OPEN-EX %-3d %s\n", f.h, zFilename);
return allocateUnixFile(&f, pId);
}
/*
** Attempt to open a new file for read-only access.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqlite3UnixOpenReadOnly(const char *zFilename, OsFile **pId){
int rc;
unixFile f;
CRASH_TEST_OVERRIDE(sqlite3CrashOpenReadOnly, zFilename, pId, 0);
assert( 0==*pId );
f.h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY);
if( f.h<0 ){
return SQLITE_CANTOPEN;
}
sqlite3OsEnterMutex();
rc = findLockInfo(f.h, &f.pLock, &f.pOpen);
sqlite3OsLeaveMutex();
if( rc ){
close(f.h);
return SQLITE_NOMEM;
}
TRACE3("OPEN-RO %-3d %s\n", f.h, zFilename);
return allocateUnixFile(&f, pId);
}
/*
** Attempt to open a file descriptor for the directory that contains a
** file. This file descriptor can be used to fsync() the directory
** in order to make sure the creation of a new file is actually written
** to disk.
**
** This routine is only meaningful for Unix. It is a no-op under
** windows since windows does not support hard links.
**
** On success, a handle for a previously open file at *id is
** updated with the new directory file descriptor and SQLITE_OK is
** returned.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id unchanged.
*/
static int unixOpenDirectory(
OsFile *id,
const char *zDirname
){
unixFile *pFile = (unixFile*)id;
if( pFile==0 ){
/* Do not open the directory if the corresponding file is not already
** open. */
return SQLITE_CANTOPEN;
}
SET_THREADID(pFile);
assert( pFile->dirfd<0 );
pFile->dirfd = open(zDirname, O_RDONLY|O_BINARY, 0);
if( pFile->dirfd<0 ){
return SQLITE_CANTOPEN;
}
TRACE3("OPENDIR %-3d %s\n", pFile->dirfd, zDirname);
return SQLITE_OK;
}
/*
** If the following global variable points to a string which is the
** name of a directory, then that directory will be used to store
** temporary files.
**
** See also the "PRAGMA temp_store_directory" SQL command.
*/
char *sqlite3_temp_directory = 0;
/*
** Create a temporary file name in zBuf. zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.
*/
int sqlite3UnixTempFileName(char *zBuf){
static const char *azDirs[] = {
0,
"/var/tmp",
"/usr/tmp",
"/tmp",
".",
};
static const unsigned char zChars[] =
"abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"0123456789";
int i, j;
struct stat buf;
const char *zDir = ".";
azDirs[0] = sqlite3_temp_directory;
for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
if( azDirs[i]==0 ) continue;
if( stat(azDirs[i], &buf) ) continue;
if( !S_ISDIR(buf.st_mode) ) continue;
if( access(azDirs[i], 07) ) continue;
zDir = azDirs[i];
break;
}
do{
sprintf(zBuf, "%s/"TEMP_FILE_PREFIX, zDir);
j = strlen(zBuf);
sqlite3Randomness(15, &zBuf[j]);
for(i=0; i<15; i++, j++){
zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
}
zBuf[j] = 0;
}while( access(zBuf,0)==0 );
return SQLITE_OK;
}
/*
** Check that a given pathname is a directory and is writable
**
*/
int sqlite3UnixIsDirWritable(char *zBuf){
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
struct stat buf;
if( zBuf==0 ) return 0;
if( zBuf[0]==0 ) return 0;
if( stat(zBuf, &buf) ) return 0;
if( !S_ISDIR(buf.st_mode) ) return 0;
if( access(zBuf, 07) ) return 0;
#endif /* SQLITE_OMIT_PAGER_PRAGMAS */
return 1;
}
/*
** Seek to the offset in id->offset then read cnt bytes into pBuf.
** Return the number of bytes actually read. Update the offset.
*/
static int seekAndRead(unixFile *id, void *pBuf, int cnt){
int got;
#ifdef USE_PREAD
got = pread(id->h, pBuf, cnt, id->offset);
#else
lseek(id->h, id->offset, SEEK_SET);
got = read(id->h, pBuf, cnt);
#endif
if( got>0 ){
id->offset += got;
}
return got;
}
/*
** Read data from a file into a buffer. Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
** wrong.
*/
static int unixRead(OsFile *id, void *pBuf, int amt){
int got;
assert( id );
SimulateIOError(SQLITE_IOERR);
TIMER_START;
got = seekAndRead((unixFile*)id, pBuf, amt);
TIMER_END;
TRACE5("READ %-3d %5d %7d %d\n", ((unixFile*)id)->h, got,
last_page, TIMER_ELAPSED);
SEEK(0);
/* if( got<0 ) got = 0; */
if( got==amt ){
return SQLITE_OK;
}else{
return SQLITE_IOERR;
}
}
/*
** Seek to the offset in id->offset then read cnt bytes into pBuf.
** Return the number of bytes actually read. Update the offset.
*/
static int seekAndWrite(unixFile *id, const void *pBuf, int cnt){
int got;
#ifdef USE_PREAD
got = pwrite(id->h, pBuf, cnt, id->offset);
#else
lseek(id->h, id->offset, SEEK_SET);
got = write(id->h, pBuf, cnt);
#endif
if( got>0 ){
id->offset += got;
}
return got;
}
/*
** Write data from a buffer into a file. Return SQLITE_OK on success
** or some other error code on failure.
*/
static int unixWrite(OsFile *id, const void *pBuf, int amt){
int wrote = 0;
assert( id );
assert( amt>0 );
SimulateIOError(SQLITE_IOERR);
SimulateDiskfullError;
TIMER_START;
while( amt>0 && (wrote = seekAndWrite((unixFile*)id, pBuf, amt))>0 ){
amt -= wrote;
pBuf = &((char*)pBuf)[wrote];
}
TIMER_END;
TRACE5("WRITE %-3d %5d %7d %d\n", ((unixFile*)id)->h, wrote,
last_page, TIMER_ELAPSED);
SEEK(0);
if( amt>0 ){
return SQLITE_FULL;
}
return SQLITE_OK;
}
/*
** Move the read/write pointer in a file.
*/
static int unixSeek(OsFile *id, i64 offset){
assert( id );
SEEK(offset/1024 + 1);
#ifdef SQLITE_TEST
if( offset ) SimulateDiskfullError
#endif
((unixFile*)id)->offset = offset;
return SQLITE_OK;
}
#ifdef SQLITE_TEST
/*
** Count the number of fullsyncs and normal syncs. This is used to test
** that syncs and fullsyncs are occuring at the right times.
*/
int sqlite3_sync_count = 0;
int sqlite3_fullsync_count = 0;
#endif
/*
** Use the fdatasync() API only if the HAVE_FDATASYNC macro is defined.
** Otherwise use fsync() in its place.
*/
#ifndef HAVE_FDATASYNC
# define fdatasync fsync
#endif
/*
** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
** the F_FULLFSYNC macro is defined. F_FULLFSYNC is currently
** only available on Mac OS X. But that could change.
*/
#ifdef F_FULLFSYNC
# define HAVE_FULLFSYNC 1
#else
# define HAVE_FULLFSYNC 0
#endif
/*
** The fsync() system call does not work as advertised on many
** unix systems. The following procedure is an attempt to make
** it work better.
**
** The SQLITE_NO_SYNC macro disables all fsync()s. This is useful
** for testing when we want to run through the test suite quickly.
** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
** or power failure will likely corrupt the database file.
*/
static int full_fsync(int fd, int fullSync, int dataOnly){
int rc;
/* Record the number of times that we do a normal fsync() and
** FULLSYNC. This is used during testing to verify that this procedure
** gets called with the correct arguments.
*/
#ifdef SQLITE_TEST
if( fullSync ) sqlite3_fullsync_count++;
sqlite3_sync_count++;
#endif
/* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
** no-op
*/
#ifdef SQLITE_NO_SYNC
rc = SQLITE_OK;
#else
#if HAVE_FULLFSYNC
if( fullSync ){
rc = fcntl(fd, F_FULLFSYNC, 0);
}else{
rc = 1;
}
/* If the FULLSYNC failed, try to do a normal fsync() */
if( rc ) rc = fsync(fd);
#else /* if !defined(F_FULLSYNC) */
if( dataOnly ){
rc = fdatasync(fd);
}else{
rc = fsync(fd);
}
#endif /* defined(F_FULLFSYNC) */
#endif /* defined(SQLITE_NO_SYNC) */
return rc;
}
/*
** Make sure all writes to a particular file are committed to disk.
**
** If dataOnly==0 then both the file itself and its metadata (file
** size, access time, etc) are synced. If dataOnly!=0 then only the
** file data is synced.
**
** Under Unix, also make sure that the directory entry for the file
** has been created by fsync-ing the directory that contains the file.
** If we do not do this and we encounter a power failure, the directory
** entry for the journal might not exist after we reboot. The next
** SQLite to access the file will not know that the journal exists (because
** the directory entry for the journal was never created) and the transaction
** will not roll back - possibly leading to database corruption.
*/
static int unixSync(OsFile *id, int dataOnly){
unixFile *pFile = (unixFile*)id;
assert( pFile );
SimulateIOError(SQLITE_IOERR);
TRACE2("SYNC %-3d\n", pFile->h);
if( full_fsync(pFile->h, pFile->fullSync, dataOnly) ){
return SQLITE_IOERR;
}
if( pFile->dirfd>=0 ){
TRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
HAVE_FULLFSYNC, pFile->fullSync);
#ifndef SQLITE_DISABLE_DIRSYNC
/* The directory sync is only attempted if full_fsync is
** turned off or unavailable. If a full_fsync occurred above,
** then the directory sync is superfluous.
*/
if( (!HAVE_FULLFSYNC || !pFile->fullSync) && full_fsync(pFile->dirfd,0,0) ){
/*
** We have received multiple reports of fsync() returning
** errors when applied to directories on certain file systems.
** A failed directory sync is not a big deal. So it seems
** better to ignore the error. Ticket #1657
*/
/* return SQLITE_IOERR; */
}
#endif
close(pFile->dirfd); /* Only need to sync once, so close the directory */
pFile->dirfd = -1; /* when we are done. */
}
return SQLITE_OK;
}
/*
** Sync the directory zDirname. This is a no-op on operating systems other
** than UNIX.
**
** This is used to make sure the master journal file has truely been deleted
** before making changes to individual journals on a multi-database commit.
** The F_FULLFSYNC option is not needed here.
*/
int sqlite3UnixSyncDirectory(const char *zDirname){
#ifdef SQLITE_DISABLE_DIRSYNC
return SQLITE_OK;
#else
int fd;
int r;
SimulateIOError(SQLITE_IOERR);
fd = open(zDirname, O_RDONLY|O_BINARY, 0);
TRACE3("DIRSYNC %-3d (%s)\n", fd, zDirname);
if( fd<0 ){
return SQLITE_CANTOPEN;
}
r = fsync(fd);
close(fd);
return ((r==0)?SQLITE_OK:SQLITE_IOERR);
#endif
}
/*
** Truncate an open file to a specified size
*/
static int unixTruncate(OsFile *id, i64 nByte){
assert( id );
SimulateIOError(SQLITE_IOERR);
return ftruncate(((unixFile*)id)->h, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
}
/*
** Determine the current size of a file in bytes
*/
static int unixFileSize(OsFile *id, i64 *pSize){
struct stat buf;
assert( id );
SimulateIOError(SQLITE_IOERR);
if( fstat(((unixFile*)id)->h, &buf)!=0 ){
return SQLITE_IOERR;
}
*pSize = buf.st_size;
return SQLITE_OK;
}
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, return
** non-zero. If the file is unlocked or holds only SHARED locks, then
** return zero.
*/
static int unixCheckReservedLock(OsFile *id){
int r = 0;
unixFile *pFile = (unixFile*)id;
assert( pFile );
sqlite3OsEnterMutex(); /* Because pFile->pLock is shared across threads */
/* Check if a thread in this process holds such a lock */
if( pFile->pLock->locktype>SHARED_LOCK ){
r = 1;
}
/* Otherwise see if some other process holds it.
*/
if( !r ){
struct flock lock;
lock.l_whence = SEEK_SET;
lock.l_start = RESERVED_BYTE;
lock.l_len = 1;
lock.l_type = F_WRLCK;
fcntl(pFile->h, F_GETLK, &lock);
if( lock.l_type!=F_UNLCK ){
r = 1;
}
}
sqlite3OsLeaveMutex();
TRACE3("TEST WR-LOCK %d %d\n", pFile->h, r);
return r;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int unixLock(OsFile *id, int locktype){
/* The following describes the implementation of the various locks and
** lock transitions in terms of the POSIX advisory shared and exclusive
** lock primitives (called read-locks and write-locks below, to avoid
** confusion with SQLite lock names). The algorithms are complicated
** slightly in order to be compatible with windows systems simultaneously
** accessing the same database file, in case that is ever required.
**
** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
** byte', each single bytes at well known offsets, and the 'shared byte
** range', a range of 510 bytes at a well known offset.
**
** To obtain a SHARED lock, a read-lock is obtained on the 'pending
** byte'. If this is successful, a random byte from the 'shared byte
** range' is read-locked and the lock on the 'pending byte' released.
**
** A process may only obtain a RESERVED lock after it has a SHARED lock.
** A RESERVED lock is implemented by grabbing a write-lock on the
** 'reserved byte'.
**
** A process may only obtain a PENDING lock after it has obtained a
** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
** on the 'pending byte'. This ensures that no new SHARED locks can be
** obtained, but existing SHARED locks are allowed to persist. A process
** does not have to obtain a RESERVED lock on the way to a PENDING lock.
** This property is used by the algorithm for rolling back a journal file
** after a crash.
**
** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
** implemented by obtaining a write-lock on the entire 'shared byte
** range'. Since all other locks require a read-lock on one of the bytes
** within this range, this ensures that no other locks are held on the
** database.
**
** The reason a single byte cannot be used instead of the 'shared byte
** range' is that some versions of windows do not support read-locks. By
** locking a random byte from a range, concurrent SHARED locks may exist
** even if the locking primitive used is always a write-lock.
*/
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
struct lockInfo *pLock = pFile->pLock;
struct flock lock;
int s;
assert( pFile );
TRACE7("LOCK %d %s was %s(%s,%d) pid=%d\n", pFile->h,
locktypeName(locktype), locktypeName(pFile->locktype),
locktypeName(pLock->locktype), pLock->cnt , getpid());
/* If there is already a lock of this type or more restrictive on the
** OsFile, do nothing. Don't use the end_lock: exit path, as
** sqlite3OsEnterMutex() hasn't been called yet.
*/
if( pFile->locktype>=locktype ){
TRACE3("LOCK %d %s ok (already held)\n", pFile->h,
locktypeName(locktype));
return SQLITE_OK;
}
/* Make sure the locking sequence is correct
*/
assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
assert( locktype!=PENDING_LOCK );
assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
/* This mutex is needed because pFile->pLock is shared across threads
*/
sqlite3OsEnterMutex();
/* Make sure the current thread owns the pFile.
*/
rc = transferOwnership(pFile);
if( rc!=SQLITE_OK ){
sqlite3OsLeaveMutex();
return rc;
}
pLock = pFile->pLock;
/* If some thread using this PID has a lock via a different OsFile*
** handle that precludes the requested lock, return BUSY.
*/
if( (pFile->locktype!=pLock->locktype &&
(pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
){
rc = SQLITE_BUSY;
goto end_lock;
}
/* If a SHARED lock is requested, and some thread using this PID already
** has a SHARED or RESERVED lock, then increment reference counts and
** return SQLITE_OK.
*/
if( locktype==SHARED_LOCK &&
(pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
assert( locktype==SHARED_LOCK );
assert( pFile->locktype==0 );
assert( pLock->cnt>0 );
pFile->locktype = SHARED_LOCK;
pLock->cnt++;
pFile->pOpen->nLock++;
goto end_lock;
}
lock.l_len = 1L;
lock.l_whence = SEEK_SET;
/* A PENDING lock is needed before acquiring a SHARED lock and before
** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will
** be released.
*/
if( locktype==SHARED_LOCK
|| (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
){
lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK);
lock.l_start = PENDING_BYTE;
s = fcntl(pFile->h, F_SETLK, &lock);
if( s ){
rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
goto end_lock;
}
}
/* If control gets to this point, then actually go ahead and make
** operating system calls for the specified lock.
*/
if( locktype==SHARED_LOCK ){
assert( pLock->cnt==0 );
assert( pLock->locktype==0 );
/* Now get the read-lock */
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
s = fcntl(pFile->h, F_SETLK, &lock);
/* Drop the temporary PENDING lock */
lock.l_start = PENDING_BYTE;
lock.l_len = 1L;
lock.l_type = F_UNLCK;
if( fcntl(pFile->h, F_SETLK, &lock)!=0 ){
rc = SQLITE_IOERR; /* This should never happen */
goto end_lock;
}
if( s ){
rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
}else{
pFile->locktype = SHARED_LOCK;
pFile->pOpen->nLock++;
pLock->cnt = 1;
}
}else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
/* We are trying for an exclusive lock but another thread in this
** same process is still holding a shared lock. */
rc = SQLITE_BUSY;
}else{
/* The request was for a RESERVED or EXCLUSIVE lock. It is
** assumed that there is a SHARED or greater lock on the file
** already.
*/
assert( 0!=pFile->locktype );
lock.l_type = F_WRLCK;
switch( locktype ){
case RESERVED_LOCK:
lock.l_start = RESERVED_BYTE;
break;
case EXCLUSIVE_LOCK:
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
break;
default:
assert(0);
}
s = fcntl(pFile->h, F_SETLK, &lock);
if( s ){
rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
}
}
if( rc==SQLITE_OK ){
pFile->locktype = locktype;
pLock->locktype = locktype;
}else if( locktype==EXCLUSIVE_LOCK ){
pFile->locktype = PENDING_LOCK;
pLock->locktype = PENDING_LOCK;
}
end_lock:
sqlite3OsLeaveMutex();
TRACE4("LOCK %d %s %s\n", pFile->h, locktypeName(locktype),
rc==SQLITE_OK ? "ok" : "failed");
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int unixUnlock(OsFile *id, int locktype){
struct lockInfo *pLock;
struct flock lock;
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
assert( pFile );
TRACE7("UNLOCK %d %d was %d(%d,%d) pid=%d\n", pFile->h, locktype,
pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid());
assert( locktype<=SHARED_LOCK );
if( pFile->locktype<=locktype ){
return SQLITE_OK;
}
if( CHECK_THREADID(pFile) ){
return SQLITE_MISUSE;
}
sqlite3OsEnterMutex();
pLock = pFile->pLock;
assert( pLock->cnt!=0 );
if( pFile->locktype>SHARED_LOCK ){
assert( pLock->locktype==pFile->locktype );
if( locktype==SHARED_LOCK ){
lock.l_type = F_RDLCK;
lock.l_whence = SEEK_SET;
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
if( fcntl(pFile->h, F_SETLK, &lock)!=0 ){
/* This should never happen */
rc = SQLITE_IOERR;
}
}
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = PENDING_BYTE;
lock.l_len = 2L; assert( PENDING_BYTE+1==RESERVED_BYTE );
if( fcntl(pFile->h, F_SETLK, &lock)==0 ){
pLock->locktype = SHARED_LOCK;
}else{
rc = SQLITE_IOERR; /* This should never happen */
}
}
if( locktype==NO_LOCK ){
struct openCnt *pOpen;
/* Decrement the shared lock counter. Release the lock using an
** OS call only when all threads in this same process have released
** the lock.
*/
pLock->cnt--;
if( pLock->cnt==0 ){
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = lock.l_len = 0L;
if( fcntl(pFile->h, F_SETLK, &lock)==0 ){
pLock->locktype = NO_LOCK;
}else{
rc = SQLITE_IOERR; /* This should never happen */
}
}
/* Decrement the count of locks against this same file. When the
** count reaches zero, close any other file descriptors whose close
** was deferred because of outstanding locks.
*/
pOpen = pFile->pOpen;
pOpen->nLock--;
assert( pOpen->nLock>=0 );
if( pOpen->nLock==0 && pOpen->nPending>0 ){
int i;
for(i=0; i<pOpen->nPending; i++){
close(pOpen->aPending[i]);
}
free(pOpen->aPending);
pOpen->nPending = 0;
pOpen->aPending = 0;
}
}
sqlite3OsLeaveMutex();
pFile->locktype = locktype;
return rc;
}
/*
** Close a file.
*/
static int unixClose(OsFile **pId){
unixFile *id = (unixFile*)*pId;
if( !id ) return SQLITE_OK;
unixUnlock(*pId, NO_LOCK);
if( id->dirfd>=0 ) close(id->dirfd);
id->dirfd = -1;
sqlite3OsEnterMutex();
if( id->pOpen->nLock ){
/* If there are outstanding locks, do not actually close the file just
** yet because that would clear those locks. Instead, add the file
** descriptor to pOpen->aPending. It will be automatically closed when
** the last lock is cleared.
*/
int *aNew;
struct openCnt *pOpen = id->pOpen;
aNew = realloc( pOpen->aPending, (pOpen->nPending+1)*sizeof(int) );
if( aNew==0 ){
/* If a malloc fails, just leak the file descriptor */
}else{
pOpen->aPending = aNew;
pOpen->aPending[pOpen->nPending] = id->h;
pOpen->nPending++;
}
}else{
/* There are no outstanding locks so we can close the file immediately */
close(id->h);
}
releaseLockInfo(id->pLock);
releaseOpenCnt(id->pOpen);
sqlite3OsLeaveMutex();
id->isOpen = 0;
TRACE2("CLOSE %-3d\n", id->h);
OpenCounter(-1);
sqlite3ThreadSafeFree(id);
*pId = 0;
return SQLITE_OK;
}
/*
** Turn a relative pathname into a full pathname. Return a pointer
** to the full pathname stored in space obtained from sqliteMalloc().
** The calling function is responsible for freeing this space once it
** is no longer needed.
*/
char *sqlite3UnixFullPathname(const char *zRelative){
char *zFull = 0;
if( zRelative[0]=='/' ){
sqlite3SetString(&zFull, zRelative, (char*)0);
}else{
char *zBuf = sqliteMalloc(5000);
if( zBuf==0 ){
return 0;
}
zBuf[0] = 0;
sqlite3SetString(&zFull, getcwd(zBuf, 5000), "/", zRelative,
(char*)0);
sqliteFree(zBuf);
}
#if 0
/*
** Remove "/./" path elements and convert "/A/./" path elements
** to just "/".
*/
if( zFull ){
int i, j;
for(i=j=0; zFull[i]; i++){
if( zFull[i]=='/' ){
if( zFull[i+1]=='/' ) continue;
if( zFull[i+1]=='.' && zFull[i+2]=='/' ){
i += 1;
continue;
}
if( zFull[i+1]=='.' && zFull[i+2]=='.' && zFull[i+3]=='/' ){
while( j>0 && zFull[j-1]!='/' ){ j--; }
i += 3;
continue;
}
}
zFull[j++] = zFull[i];
}
zFull[j] = 0;
}
#endif
return zFull;
}
/*
** Change the value of the fullsync flag in the given file descriptor.
*/
static void unixSetFullSync(OsFile *id, int v){
((unixFile*)id)->fullSync = v;
}
/*
** Return the underlying file handle for an OsFile
*/
static int unixFileHandle(OsFile *id){
return ((unixFile*)id)->h;
}
/*
** Return an integer that indices the type of lock currently held
** by this handle. (Used for testing and analysis only.)
*/
static int unixLockState(OsFile *id){
return ((unixFile*)id)->locktype;
}
/*
** This vector defines all the methods that can operate on an OsFile
** for unix.
*/
static const IoMethod sqlite3UnixIoMethod = {
unixClose,
unixOpenDirectory,
unixRead,
unixWrite,
unixSeek,
unixTruncate,
unixSync,
unixSetFullSync,
unixFileHandle,
unixFileSize,
unixLock,
unixUnlock,
unixLockState,
unixCheckReservedLock,
};
/*
** Allocate memory for a unixFile. Initialize the new unixFile
** to the value given in pInit and return a pointer to the new
** OsFile. If we run out of memory, close the file and return NULL.
*/
static int allocateUnixFile(unixFile *pInit, OsFile **pId){
unixFile *pNew;
pInit->dirfd = -1;
pInit->fullSync = 0;
pInit->locktype = 0;
pInit->offset = 0;
SET_THREADID(pInit);
pNew = sqlite3ThreadSafeMalloc( sizeof(unixFile) );
if( pNew==0 ){
close(pInit->h);
sqlite3OsEnterMutex();
releaseLockInfo(pInit->pLock);
releaseOpenCnt(pInit->pOpen);
sqlite3OsLeaveMutex();
*pId = 0;
return SQLITE_NOMEM;
}else{
*pNew = *pInit;
pNew->pMethod = &sqlite3UnixIoMethod;
*pId = (OsFile*)pNew;
OpenCounter(+1);
return SQLITE_OK;
}
}
#endif /* SQLITE_OMIT_DISKIO */
/***************************************************************************
** Everything above deals with file I/O. Everything that follows deals
** with other miscellanous aspects of the operating system interface
****************************************************************************/
/*
** Get information to seed the random number generator. The seed
** is written into the buffer zBuf[256]. The calling function must
** supply a sufficiently large buffer.
*/
int sqlite3UnixRandomSeed(char *zBuf){
/* We have to initialize zBuf to prevent valgrind from reporting
** errors. The reports issued by valgrind are incorrect - we would
** prefer that the randomness be increased by making use of the
** uninitialized space in zBuf - but valgrind errors tend to worry
** some users. Rather than argue, it seems easier just to initialize
** the whole array and silence valgrind, even if that means less randomness
** in the random seed.
**
** When testing, initializing zBuf[] to zero is all we do. That means
** that we always use the same random number sequence. This makes the
** tests repeatable.
*/
memset(zBuf, 0, 256);
#if !defined(SQLITE_TEST)
{
int pid, fd;
fd = open("/dev/urandom", O_RDONLY);
if( fd<0 ){
time_t t;
time(&t);
memcpy(zBuf, &t, sizeof(t));
pid = getpid();
memcpy(&zBuf[sizeof(time_t)], &pid, sizeof(pid));
}else{
read(fd, zBuf, 256);
close(fd);
}
}
#endif
return SQLITE_OK;
}
/*
** Sleep for a little while. Return the amount of time slept.
** The argument is the number of milliseconds we want to sleep.
*/
int sqlite3UnixSleep(int ms){
#if defined(HAVE_USLEEP) && HAVE_USLEEP
usleep(ms*1000);
return ms;
#else
sleep((ms+999)/1000);
return 1000*((ms+999)/1000);
#endif
}
/*
** Static variables used for thread synchronization.
**
** inMutex the nesting depth of the recursive mutex. The thread
** holding mutexMain can read this variable at any time.
** But is must hold mutexAux to change this variable. Other
** threads must hold mutexAux to read the variable and can
** never write.
**
** mutexOwner The thread id of the thread holding mutexMain. Same
** access rules as for inMutex.
**
** mutexOwnerValid True if the value in mutexOwner is valid. The same
** access rules apply as for inMutex.
**
** mutexMain The main mutex. Hold this mutex in order to get exclusive
** access to SQLite data structures.
**
** mutexAux An auxiliary mutex needed to access variables defined above.
**
** Mutexes are always acquired in this order: mutexMain mutexAux. It
** is not necessary to acquire mutexMain in order to get mutexAux - just
** do not attempt to acquire them in the reverse order: mutexAux mutexMain.
** Either get the mutexes with mutexMain first or get mutexAux only.
**
** When running on a platform where the three variables inMutex, mutexOwner,
** and mutexOwnerValid can be set atomically, the mutexAux is not required.
** On many systems, all three are 32-bit integers and writing to a 32-bit
** integer is atomic. I think. But there are no guarantees. So it seems
** safer to protect them using mutexAux.
*/
static int inMutex = 0;
#ifdef SQLITE_UNIX_THREADS
static pthread_t mutexOwner; /* Thread holding mutexMain */
static int mutexOwnerValid = 0; /* True if mutexOwner is valid */
static pthread_mutex_t mutexMain = PTHREAD_MUTEX_INITIALIZER; /* The mutex */
static pthread_mutex_t mutexAux = PTHREAD_MUTEX_INITIALIZER; /* Aux mutex */
#endif
/*
** The following pair of routine implement mutual exclusion for
** multi-threaded processes. Only a single thread is allowed to
** executed code that is surrounded by EnterMutex() and LeaveMutex().
**
** SQLite uses only a single Mutex. There is not much critical
** code and what little there is executes quickly and without blocking.
**
** As of version 3.3.2, this mutex must be recursive.
*/
void sqlite3UnixEnterMutex(){
#ifdef SQLITE_UNIX_THREADS
pthread_mutex_lock(&mutexAux);
if( !mutexOwnerValid || !pthread_equal(mutexOwner, pthread_self()) ){
pthread_mutex_unlock(&mutexAux);
pthread_mutex_lock(&mutexMain);
assert( inMutex==0 );
assert( !mutexOwnerValid );
pthread_mutex_lock(&mutexAux);
mutexOwner = pthread_self();
mutexOwnerValid = 1;
}
inMutex++;
pthread_mutex_unlock(&mutexAux);
#else
inMutex++;
#endif
}
void sqlite3UnixLeaveMutex(){
assert( inMutex>0 );
#ifdef SQLITE_UNIX_THREADS
pthread_mutex_lock(&mutexAux);
inMutex--;
assert( pthread_equal(mutexOwner, pthread_self()) );
if( inMutex==0 ){
assert( mutexOwnerValid );
mutexOwnerValid = 0;
pthread_mutex_unlock(&mutexMain);
}
pthread_mutex_unlock(&mutexAux);
#else
inMutex--;
#endif
}
/*
** Return TRUE if the mutex is currently held.
**
** If the thisThrd parameter is true, return true only if the
** calling thread holds the mutex. If the parameter is false, return
** true if any thread holds the mutex.
*/
int sqlite3UnixInMutex(int thisThrd){
#ifdef SQLITE_UNIX_THREADS
int rc;
pthread_mutex_lock(&mutexAux);
rc = inMutex>0 && (thisThrd==0 || pthread_equal(mutexOwner,pthread_self()));
pthread_mutex_unlock(&mutexAux);
return rc;
#else
return inMutex>0;
#endif
}
/*
** Remember the number of thread-specific-data blocks allocated.
** Use this to verify that we are not leaking thread-specific-data.
** Ticket #1601
*/
#ifdef SQLITE_TEST
int sqlite3_tsd_count = 0;
# ifdef SQLITE_UNIX_THREADS
static pthread_mutex_t tsd_counter_mutex = PTHREAD_MUTEX_INITIALIZER;
# define TSD_COUNTER(N) \
pthread_mutex_lock(&tsd_counter_mutex); \
sqlite3_tsd_count += N; \
pthread_mutex_unlock(&tsd_counter_mutex);
# else
# define TSD_COUNTER(N) sqlite3_tsd_count += N
# endif
#else
# define TSD_COUNTER(N) /* no-op */
#endif
/*
** If called with allocateFlag>0, then return a pointer to thread
** specific data for the current thread. Allocate and zero the
** thread-specific data if it does not already exist.
**
** If called with allocateFlag==0, then check the current thread
** specific data. Return it if it exists. If it does not exist,
** then return NULL.
**
** If called with allocateFlag<0, check to see if the thread specific
** data is allocated and is all zero. If it is then deallocate it.
** Return a pointer to the thread specific data or NULL if it is
** unallocated or gets deallocated.
*/
ThreadData *sqlite3UnixThreadSpecificData(int allocateFlag){
static const ThreadData zeroData = {0}; /* Initializer to silence warnings
** from broken compilers */
#ifdef SQLITE_UNIX_THREADS
static pthread_key_t key;
static int keyInit = 0;
ThreadData *pTsd;
if( !keyInit ){
sqlite3OsEnterMutex();
if( !keyInit ){
int rc;
rc = pthread_key_create(&key, 0);
if( rc ){
sqlite3OsLeaveMutex();
return 0;
}
keyInit = 1;
}
sqlite3OsLeaveMutex();
}
pTsd = pthread_getspecific(key);
if( allocateFlag>0 ){
if( pTsd==0 ){
if( !sqlite3TestMallocFail() ){
pTsd = sqlite3OsMalloc(sizeof(zeroData));
}
#ifdef SQLITE_MEMDEBUG
sqlite3_isFail = 0;
#endif
if( pTsd ){
*pTsd = zeroData;
pthread_setspecific(key, pTsd);
TSD_COUNTER(+1);
}
}
}else if( pTsd!=0 && allocateFlag<0
&& memcmp(pTsd, &zeroData, sizeof(ThreadData))==0 ){
sqlite3OsFree(pTsd);
pthread_setspecific(key, 0);
TSD_COUNTER(-1);
pTsd = 0;
}
return pTsd;
#else
static ThreadData *pTsd = 0;
if( allocateFlag>0 ){
if( pTsd==0 ){
if( !sqlite3TestMallocFail() ){
pTsd = sqlite3OsMalloc( sizeof(zeroData) );
}
#ifdef SQLITE_MEMDEBUG
sqlite3_isFail = 0;
#endif
if( pTsd ){
*pTsd = zeroData;
TSD_COUNTER(+1);
}
}
}else if( pTsd!=0 && allocateFlag<0
&& memcmp(pTsd, &zeroData, sizeof(ThreadData))==0 ){
sqlite3OsFree(pTsd);
TSD_COUNTER(-1);
pTsd = 0;
}
return pTsd;
#endif
}
/*
** The following variable, if set to a non-zero value, becomes the result
** returned from sqlite3OsCurrentTime(). This is used for testing.
*/
#ifdef SQLITE_TEST
int sqlite3_current_time = 0;
#endif
/*
** Find the current time (in Universal Coordinated Time). Write the
** current time and date as a Julian Day number into *prNow and
** return 0. Return 1 if the time and date cannot be found.
*/
int sqlite3UnixCurrentTime(double *prNow){
#ifdef NO_GETTOD
time_t t;
time(&t);
*prNow = t/86400.0 + 2440587.5;
#else
struct timeval sNow;
struct timezone sTz; /* Not used */
gettimeofday(&sNow, &sTz);
*prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0;
#endif
#ifdef SQLITE_TEST
if( sqlite3_current_time ){
*prNow = sqlite3_current_time/86400.0 + 2440587.5;
}
#endif
return 0;
}
#endif /* OS_UNIX */
Submit an article or tip