** Either unixShmNode.pShmMutex must be held or unixShmNode.nRef==0 and
** unixMutexHeld() is true when reading or writing any other field
** in this structure.
+**
+** aLock[SQLITE_SHM_NLOCK]:
+** This array records the various locks held by clients on each of the
+** SQLITE_SHM_NLOCK slots. If the aLock[] entry is set to 0, then no
+** locks are held by the process on this slot. If it is set to -1, then
+** some client holds an EXCLUSIVE lock on the locking slot. If the aLock[]
+** value is set to a positive value, then it is the number of shared
+** locks currently held on the slot.
+**
+** aMutex[SQLITE_SHM_NLOCK]:
+** Normally, when SQLITE_ENABLE_SETLK_TIMEOUT is not defined, mutex
+** pShmMutex is used to protect the aLock[] array and the right to
+** call fcntl() on unixShmNode.hShm to obtain or release locks.
+**
+** If SQLITE_ENABLE_SETLK_TIMEOUT is defined though, we use an array
+** of mutexes - one for each locking slot. To read or write locking
+** slot aLock[iSlot], the caller must hold the corresponding mutex
+** aMutex[iSlot]. Similarly, to call fcntl() to obtain or release a
+** lock corresponding to slot iSlot, mutex aMutex[iSlot] must be held.
*/
struct unixShmNode {
unixInodeInfo *pInode; /* unixInodeInfo that owns this SHM node */
char **apRegion; /* Array of mapped shared-memory regions */
int nRef; /* Number of unixShm objects pointing to this */
unixShm *pFirst; /* All unixShm objects pointing to this */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ sqlite3_mutex *aMutex[SQLITE_SHM_NLOCK];
+#endif
int aLock[SQLITE_SHM_NLOCK]; /* # shared locks on slot, -1==excl lock */
#ifdef SQLITE_DEBUG
- u8 exclMask; /* Mask of exclusive locks held */
- u8 sharedMask; /* Mask of shared locks held */
u8 nextShmId; /* Next available unixShm.id value */
#endif
};
struct flock f; /* The posix advisory locking structure */
int rc = SQLITE_OK; /* Result code form fcntl() */
- /* Access to the unixShmNode object is serialized by the caller */
pShmNode = pFile->pInode->pShmNode;
- assert( pShmNode->nRef==0 || sqlite3_mutex_held(pShmNode->pShmMutex) );
- assert( pShmNode->nRef>0 || unixMutexHeld() );
+
+ /* Assert that the correct mutex or mutexes are held. */
+ if( pShmNode->nRef==0 ){
+ assert( ofst==UNIX_SHM_DMS && n==1 && unixMutexHeld() );
+ }else{
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ int ii;
+ for(ii=ofst-UNIX_SHM_BASE; ii<ofst-UNIX_SHM_BASE+n; ii++){
+ assert( sqlite3_mutex_held(pShmNode->aMutex[ii]) );
+ }
+#else
+ assert( sqlite3_mutex_held(pShmNode->pShmMutex) );
+ assert( pShmNode->nRef>0 );
+#endif
+ }
/* Shared locks never span more than one byte */
assert( n==1 || lockType!=F_RDLCK );
/* Locks are within range */
assert( n>=1 && n<=SQLITE_SHM_NLOCK );
+ assert( ofst>=UNIX_SHM_BASE && ofst<=(UNIX_SHM_DMS+SQLITE_SHM_NLOCK) );
if( pShmNode->hShm>=0 ){
int res;
}
}
- /* Update the global lock state and do debug tracing */
+ /* Do debug tracing */
#ifdef SQLITE_DEBUG
- { u16 mask;
OSTRACE(("SHM-LOCK "));
- mask = ofst>31 ? 0xffff : (1<<(ofst+n)) - (1<<ofst);
if( rc==SQLITE_OK ){
if( lockType==F_UNLCK ){
- OSTRACE(("unlock %d ok", ofst));
- pShmNode->exclMask &= ~mask;
- pShmNode->sharedMask &= ~mask;
+ OSTRACE(("unlock %d..%d ok\n", ofst, ofst+n-1));
}else if( lockType==F_RDLCK ){
- OSTRACE(("read-lock %d ok", ofst));
- pShmNode->exclMask &= ~mask;
- pShmNode->sharedMask |= mask;
+ OSTRACE(("read-lock %d..%d ok\n", ofst, ofst+n-1));
}else{
assert( lockType==F_WRLCK );
- OSTRACE(("write-lock %d ok", ofst));
- pShmNode->exclMask |= mask;
- pShmNode->sharedMask &= ~mask;
+ OSTRACE(("write-lock %d..%d ok\n", ofst, ofst+n-1));
}
}else{
if( lockType==F_UNLCK ){
- OSTRACE(("unlock %d failed", ofst));
+ OSTRACE(("unlock %d..%d failed\n", ofst, ofst+n-1));
}else if( lockType==F_RDLCK ){
- OSTRACE(("read-lock failed"));
+ OSTRACE(("read-lock %d..%d failed\n", ofst, ofst+n-1));
}else{
assert( lockType==F_WRLCK );
- OSTRACE(("write-lock %d failed", ofst));
+ OSTRACE(("write-lock %d..%d failed\n", ofst, ofst+n-1));
}
}
- OSTRACE((" - afterwards %03x,%03x\n",
- pShmNode->sharedMask, pShmNode->exclMask));
- }
#endif
return rc;
int i;
assert( p->pInode==pFd->pInode );
sqlite3_mutex_free(p->pShmMutex);
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ for(i=0; i<SQLITE_SHM_NLOCK; i++){
+ sqlite3_mutex_free(p->aMutex[i]);
+ }
+#endif
for(i=0; i<p->nRegion; i+=nShmPerMap){
if( p->hShm>=0 ){
osMunmap(p->apRegion[i], p->szRegion);
rc = SQLITE_NOMEM_BKPT;
goto shm_open_err;
}
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ {
+ int ii;
+ for(ii=0; ii<SQLITE_SHM_NLOCK; ii++){
+ pShmNode->aMutex[ii] = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+ if( pShmNode->aMutex[ii]==0 ){
+ rc = SQLITE_NOMEM_BKPT;
+ goto shm_open_err;
+ }
+ }
+ }
+#endif
}
if( pInode->bProcessLock==0 ){
*/
#ifdef SQLITE_DEBUG
static int assertLockingArrayOk(unixShmNode *pShmNode){
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ return 1;
+#else
unixShm *pX;
int aLock[SQLITE_SHM_NLOCK];
- assert( sqlite3_mutex_held(pShmNode->pShmMutex) );
memset(aLock, 0, sizeof(aLock));
for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
assert( 0==memcmp(pShmNode->aLock, aLock, sizeof(aLock)) );
return (memcmp(pShmNode->aLock, aLock, sizeof(aLock))==0);
+#endif
}
#endif
/*
** Change the lock state for a shared-memory segment.
**
-** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
+** Note that the relationship between SHARED and EXCLUSIVE locks is a little
** different here than in posix. In xShmLock(), one can go from unlocked
** to shared and back or from unlocked to exclusive and back. But one may
** not go from shared to exclusive or from exclusive to shared.
unixShm *p; /* The shared memory being locked */
unixShmNode *pShmNode; /* The underlying file iNode */
int rc = SQLITE_OK; /* Result code */
- u16 mask; /* Mask of locks to take or release */
+ u16 mask = (1<<(ofst+n)) - (1<<ofst); /* Mask of locks to take or release */
int *aLock;
p = pDbFd->pShm;
}
#endif
- mask = (1<<(ofst+n)) - (1<<ofst);
- assert( n>1 || mask==(1<<ofst) );
- sqlite3_mutex_enter(pShmNode->pShmMutex);
- assert( assertLockingArrayOk(pShmNode) );
- if( flags & SQLITE_SHM_UNLOCK ){
- if( (p->exclMask|p->sharedMask) & mask ){
- int ii;
- int bUnlock = 1;
+ /* Check if there is any work to do. There are three cases:
+ **
+ ** a) An unlock operation where there are locks to unlock,
+ ** b) An shared lock where the requested lock is not already held
+ ** c) An exclusive lock where the requested lock is not already held
+ **
+ ** The SQLite core never requests an exclusive lock that it already holds.
+ ** This is assert()ed below.
+ */
+ assert( flags!=(SQLITE_SHM_EXCLUSIVE|SQLITE_SHM_LOCK)
+ || 0==(p->exclMask & mask)
+ );
+ if( ((flags & SQLITE_SHM_UNLOCK) && ((p->exclMask|p->sharedMask) & mask))
+ || (flags==(SQLITE_SHM_SHARED|SQLITE_SHM_LOCK) && 0==(p->sharedMask & mask))
+ || (flags==(SQLITE_SHM_EXCLUSIVE|SQLITE_SHM_LOCK))
+ ){
- for(ii=ofst; ii<ofst+n; ii++){
- if( aLock[ii]>((p->sharedMask & (1<<ii)) ? 1 : 0) ){
+ /* Take the required mutexes */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ int iMutex;
+ for(iMutex=ofst; iMutex<ofst+n; iMutex++){
+ sqlite3_mutex_enter(pShmNode->aMutex[iMutex]);
+ }
+#else
+ sqlite3_mutex_enter(pShmNode->pShmMutex);
+#endif
+
+ if( flags & SQLITE_SHM_UNLOCK ){
+ /* Case (a) - unlock. */
+ int bUnlock = 1;
+ assert( (p->exclMask & p->sharedMask)==0 );
+ assert( (flags & SQLITE_SHM_EXCLUSIVE)==0 || (p->exclMask & mask)==mask );
+ assert( (flags & SQLITE_SHM_SHARED)==0 || (p->sharedMask & mask)==mask );
+
+ /* If this is a SHARED lock being unlocked, it is possible that other
+ ** clients within this process are holding the same SHARED lock. In
+ ** this case, set bUnlock to 0 so that the posix lock is not removed
+ ** from the file-descriptor below. */
+ if( flags & SQLITE_SHM_SHARED ){
+ assert( n==1 );
+ assert( aLock[ofst]>=1 );
+ if( aLock[ofst]>1 ){
bUnlock = 0;
+ aLock[ofst]--;
+ p->sharedMask &= ~mask;
}
}
rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
if( rc==SQLITE_OK ){
memset(&aLock[ofst], 0, sizeof(int)*n);
+ p->sharedMask &= ~mask;
+ p->exclMask &= ~mask;
}
- }else if( ALWAYS(p->sharedMask & (1<<ofst)) ){
- assert( n==1 && aLock[ofst]>1 );
- aLock[ofst]--;
}
+ }else if( flags & SQLITE_SHM_SHARED ){
+ /* Case (b) - a shared lock. */
- /* Undo the local locks */
- if( rc==SQLITE_OK ){
- p->exclMask &= ~mask;
- p->sharedMask &= ~mask;
- }
- }
- }else if( flags & SQLITE_SHM_SHARED ){
- assert( n==1 );
- assert( (p->exclMask & (1<<ofst))==0 );
- if( (p->sharedMask & mask)==0 ){
if( aLock[ofst]<0 ){
+ /* An exclusive lock is held by some other connection. BUSY. */
rc = SQLITE_BUSY;
}else if( aLock[ofst]==0 ){
rc = unixShmSystemLock(pDbFd, F_RDLCK, ofst+UNIX_SHM_BASE, n);
p->sharedMask |= mask;
aLock[ofst]++;
}
- }
- }else{
- /* Make sure no sibling connections hold locks that will block this
- ** lock. If any do, return SQLITE_BUSY right away. */
- int ii;
- for(ii=ofst; ii<ofst+n; ii++){
+ }else{
+ /* Case (c) - an exclusive lock. */
+ int ii;
+
+ assert( flags==(SQLITE_SHM_LOCK|SQLITE_SHM_EXCLUSIVE) );
assert( (p->sharedMask & mask)==0 );
- if( ALWAYS((p->exclMask & (1<<ii))==0) && aLock[ii] ){
- rc = SQLITE_BUSY;
- break;
+ assert( (p->exclMask & mask)==0 );
+
+ /* Make sure no sibling connections hold locks that will block this
+ ** lock. If any do, return SQLITE_BUSY right away. */
+ for(ii=ofst; ii<ofst+n; ii++){
+ if( aLock[ii] ){
+ rc = SQLITE_BUSY;
+ break;
+ }
}
- }
- /* Get the exclusive locks at the system level. Then if successful
- ** also update the in-memory values. */
- if( rc==SQLITE_OK ){
- rc = unixShmSystemLock(pDbFd, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+ /* Get the exclusive locks at the system level. Then if successful
+ ** also update the in-memory values. */
if( rc==SQLITE_OK ){
- assert( (p->sharedMask & mask)==0 );
- p->exclMask |= mask;
- for(ii=ofst; ii<ofst+n; ii++){
- aLock[ii] = -1;
+ rc = unixShmSystemLock(pDbFd, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+ if( rc==SQLITE_OK ){
+ p->exclMask |= mask;
+ for(ii=ofst; ii<ofst+n; ii++){
+ aLock[ii] = -1;
+ }
}
}
}
+
+ assert( assertLockingArrayOk(pShmNode) );
+
+ /* Drop the mutexes acquired above. */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+ for(iMutex=ofst; iMutex<ofst+n; iMutex++){
+ sqlite3_mutex_leave(pShmNode->aMutex[iMutex]);
+ }
+#else
+ sqlite3_mutex_leave(pShmNode->pShmMutex);
+#endif
}
- assert( assertLockingArrayOk(pShmNode) );
- sqlite3_mutex_leave(pShmNode->pShmMutex);
+
OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
p->id, osGetpid(0), p->sharedMask, p->exclMask));
return rc;
projects / thirdparty / sqlite.git / commitdiff
