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Stop requiring the global VFS mutex to access the unixInodeInfo.pUnused field.

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The unixInodeInfo mutex is sufficient.

FossilOrigin-Name: e3ea43dabf099dc2954c23d348638e7b2a8b9122d2994154bc649a2c09260c46
This commit is contained in:
drh
2018-08-13 22:50:34 +00:00
parent 095908e1c7
commit ef52b36a6b
3 changed files with 34 additions and 46 deletions
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66
src/os_unix.c
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@@ -1126,17 +1126,13 @@ struct unixFileId {
**
** (1) Only the pLockMutex mutex must be held in order to read or write
** any of the locking fields:
** nShared, nLock, eFileLock, or bProcessLock
** nShared, nLock, eFileLock, bProcessLock, pUnused
**
** (2) When nRef>0, then the following fields are unchanging and can
** be read (but not written) without holding any mutex:
** fileId, pLockMutex
**
** (3) The pUnused field may only be changed while holding bo the
** pLockMutex and the bigUnixLock mutex. But it may be read
** while holding either.
**
** (4) With the exceptions above, all the fields may only be read
** (3) With the exceptions above, all the fields may only be read
** or written while holding the global unixBigLock mutex.
**
** Deadlock prevention: The global unixBigLock mutex may not
@@ -1150,7 +1146,7 @@ struct unixInodeInfo {
int nLock; /* Number of outstanding file locks */
unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
unsigned char bProcessLock; /* An exclusive process lock is held */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
int nRef; /* Number of pointers to this structure */
unixShmNode *pShmNode; /* Shared memory associated with this inode */
unixInodeInfo *pNext; /* List of all unixInodeInfo objects */
@@ -1288,16 +1284,13 @@ static void closePendingFds(unixFile *pFile){
unixInodeInfo *pInode = pFile->pInode;
UnixUnusedFd *p;
UnixUnusedFd *pNext;
assert( unixMutexHeld() );
assert( unixFileMutexNotheld(pFile) );
sqlite3_mutex_enter(pInode->pLockMutex);
assert( unixFileMutexHeld(pFile) );
for(p=pInode->pUnused; p; p=pNext){
pNext = p->pNext;
robust_close(pFile, p->fd, __LINE__);
sqlite3_free(p);
}
pInode->pUnused = 0;
sqlite3_mutex_leave(pInode->pLockMutex);
}
/*
@@ -1314,7 +1307,9 @@ static void releaseInodeInfo(unixFile *pFile){
pInode->nRef--;
if( pInode->nRef==0 ){
assert( pInode->pShmNode==0 );
sqlite3_mutex_enter(pInode->pLockMutex);
closePendingFds(pFile);
sqlite3_mutex_leave(pInode->pLockMutex);
if( pInode->pPrev ){
assert( pInode->pPrev->pNext==pInode );
pInode->pPrev->pNext = pInode->pNext;
@@ -1863,12 +1858,9 @@ end_lock:
static void setPendingFd(unixFile *pFile){
unixInodeInfo *pInode = pFile->pInode;
UnixUnusedFd *p = pFile->pPreallocatedUnused;
assert( unixMutexHeld() );
assert( unixFileMutexNotheld(pFile) );
sqlite3_mutex_enter(pInode->pLockMutex);
assert( unixFileMutexHeld(pFile) );
p->pNext = pInode->pUnused;
pInode->pUnused = p;
sqlite3_mutex_leave(pInode->pLockMutex);
pFile->h = -1;
pFile->pPreallocatedUnused = 0;
}
@@ -1891,7 +1883,6 @@ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
unixInodeInfo *pInode;
struct flock lock;
int rc = SQLITE_OK;
int wantToClosePending = 0; /* True to try to close file old descriptors */
assert( pFile );
OSTRACE(("UNLOCK %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
@@ -2029,20 +2020,13 @@ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
*/
pInode->nLock--;
assert( pInode->nLock>=0 );
if( pInode->nLock==0 && pInode->pUnused!=0 ){
wantToClosePending = 1;
}
if( pInode->nLock==0 ) closePendingFds(pFile);
}
end_unlock:
sqlite3_mutex_leave(pInode->pLockMutex);
if( rc==SQLITE_OK ){
pFile->eFileLock = eFileLock;
if( wantToClosePending ){
unixEnterMutex();
if( pInode->nLock==0 ) closePendingFds(pFile);
unixLeaveMutex();
}
}
return rc;
}
@@ -2114,6 +2098,9 @@ static int closeUnixFile(sqlite3_file *id){
static int unixClose(sqlite3_file *id){
int rc = SQLITE_OK;
unixFile *pFile = (unixFile *)id;
unixInodeInfo *pInode = pFile->pInode;
assert( pInode!=0 );
verifyDbFile(pFile);
unixUnlock(id, NO_LOCK);
assert( unixFileMutexNotheld(pFile) );
@@ -2123,7 +2110,8 @@ static int unixClose(sqlite3_file *id){
** routine (e.g. nolockClose()) would be called instead.
*/
assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 );
if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){
sqlite3_mutex_enter(pInode->pLockMutex);
if( pFile->pInode->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 pInode->pUnused list. It will be automatically closed
@@ -2131,6 +2119,7 @@ static int unixClose(sqlite3_file *id){
*/
setPendingFd(pFile);
}
sqlite3_mutex_leave(pInode->pLockMutex);
releaseInodeInfo(pFile);
rc = closeUnixFile(id);
unixLeaveMutex();
@@ -3086,7 +3075,6 @@ static int afpUnlock(sqlite3_file *id, int eFileLock) {
unixInodeInfo *pInode;
afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
int skipShared = 0;
int wantToClosePending = 0;
#ifdef SQLITE_TEST
int h = pFile->h;
#endif
@@ -3170,18 +3158,13 @@ static int afpUnlock(sqlite3_file *id, int eFileLock) {
if( rc==SQLITE_OK ){
pInode->nLock--;
assert( pInode->nLock>=0 );
if( pInode->nLock==0 && pInode->pUnused!=0 ) wantToClosePending = 1;
if( pInode->nLock==0 ) closePendingFds(pFile);
}
}
sqlite3_mutex_leave(pInode->pLockMutex);
if( rc==SQLITE_OK ){
pFile->eFileLock = eFileLock;
if( wantToClosePending ){
unixEnterMutex();
if( pInode->nLock==0 ) closePendingFds(pFile);
unixLeaveMutex();
}
}
return rc;
}
@@ -3196,13 +3179,18 @@ static int afpClose(sqlite3_file *id) {
afpUnlock(id, NO_LOCK);
assert( unixFileMutexNotheld(pFile) );
unixEnterMutex();
if( pFile->pInode && pFile->pInode->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 pInode->aPending. It will be automatically closed when
** the last lock is cleared.
*/
setPendingFd(pFile);
if( pFile->pInode ){
unixInodeInfo *pInode = pFile->pInode;
sqlite3_mutex_enter(pInode->pLockMutex);
if( pFile->pInode->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 pInode->aPending. It will be automatically closed when
** the last lock is cleared.
*/
setPendingFd(pFile);
}
sqlite3_mutex_leave(pInode->pLockMutex);
}
releaseInodeInfo(pFile);
sqlite3_free(pFile->lockingContext);