database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-11-14 00:22:38 +03:00
Code Activity

Remove the BtreeMutexArray object - use the Vdbe.btreeMask field to accomplish

Browse Source 
the same result.  Add a generation counter to btree mutexes in order to assert
that mutexes are never temporarily dropped over a range of instructions in order
to do deadlock avoidance in some subroutine.  Lock all btrees in any Vdbe
program that uses OP_ParseSchema.

FossilOrigin-Name: d81708f7d1eee399bfe76f6b8dac950a85dc2582
This commit is contained in:
drh
2011-04-04 00:14:43 +00:00
parent dddd779b2b
commit bdaec52c62
8 changed files with 242 additions and 198 deletions
Download Patch File Download Diff File Expand all files Collapse all files

164
src/vdbeaux.c
View File

@@ -157,6 +157,11 @@ int sqlite3VdbeAddOp3(Vdbe *p, int op, int p1, int p2, int p3){
pOp->p4.p = 0;
pOp->p4type = P4_NOTUSED;
p->expired = 0;
if( op==OP_ParseSchema ){
/* Any program that uses the OP_ParseSchema opcode needs to lock
** all btrees. */
p->btreeMask = ~(yDbMask)0;
}
#ifdef SQLITE_DEBUG
pOp->zComment = 0;
if( sqlite3VdbeAddopTrace ) sqlite3VdbePrintOp(0, i, &p->aOp[i]);
@@ -457,7 +462,7 @@ VdbeOp *sqlite3VdbeTakeOpArray(Vdbe *p, int *pnOp, int *pnMaxArg){
assert( aOp && !p->db->mallocFailed );
/* Check that sqlite3VdbeUsesBtree() was not called on this VM */
assert( p->aMutex.nMutex==0 );
assert( p->btreeMask==0 );
resolveP2Values(p, pnMaxArg);
*pnOp = p->nOp;
@@ -945,22 +950,123 @@ static char *displayP4(Op *pOp, char *zTemp, int nTemp){
/*
** Declare to the Vdbe that the BTree object at db->aDb[i] is used.
**
** The prepared statement has to know in advance which Btree objects
** will be used so that it can acquire mutexes on them all in sorted
** order (via sqlite3VdbeMutexArrayEnter(). Mutexes are acquired
** in order (and released in reverse order) to avoid deadlocks.
** The prepared statements need to know in advance the complete set of
** attached databases that they will be using. A mask of these databases
** is maintained in p->btreeMask and is used for locking and other purposes.
*/
void sqlite3VdbeUsesBtree(Vdbe *p, int i){
yDbMask mask;
assert( i>=0 && i<p->db->nDb && i<sizeof(yDbMask)*8 );
assert( i<(int)sizeof(p->btreeMask)*8 );
mask = ((yDbMask)1)<<i;
if( (p->btreeMask & mask)==0 ){
p->btreeMask |= mask;
sqlite3BtreeMutexArrayInsert(&p->aMutex, p->db->aDb[i].pBt);
}
p->btreeMask |= ((yDbMask)1)<<i;
}
/*
** Compute the sum of all mutex counters for all btrees in the
** given prepared statement.
*/
#ifndef SQLITE_OMIT_SHARED_CACHE
static u32 mutexCounterSum(Vdbe *p){
u32 cntSum = 0;
#ifdef SQLITE_DEBUG
int i;
yDbMask mask;
sqlite3 *db = p->db;
Db *aDb = db->aDb;
int nDb = db->nDb;
for(i=0, mask=1; i<nDb; i++, mask += mask){
if( i!=1 && (mask & p->btreeMask)!=0 && ALWAYS(aDb[i].pBt!=0) ){
cntSum += sqlite3BtreeMutexCounter(aDb[i].pBt);
}
}
#endif
return cntSum;
}
#endif
/*
** If SQLite is compiled to support shared-cache mode and to be threadsafe,
** this routine obtains the mutex associated with each BtShared structure
** that may be accessed by the VM passed as an argument. In doing so it also
** sets the BtShared.db member of each of the BtShared structures, ensuring
** that the correct busy-handler callback is invoked if required.
**
** If SQLite is not threadsafe but does support shared-cache mode, then
** sqlite3BtreeEnter() is invoked to set the BtShared.db variables
** of all of BtShared structures accessible via the database handle
** associated with the VM.
**
** If SQLite is not threadsafe and does not support shared-cache mode, this
** function is a no-op.
**
** The p->btreeMask field is a bitmask of all btrees that the prepared
** statement p will ever use. Let N be the number of bits in p->btreeMask
** corresponding to btrees that use shared cache. Then the runtime of
** this routine is N*N. But as N is rarely more than 1, this should not
** be a problem.
*/
void sqlite3VdbeEnter(Vdbe *p){
#ifndef SQLITE_OMIT_SHARED_CACHE
int i;
yDbMask mask;
sqlite3 *db = p->db;
Db *aDb = db->aDb;
int nDb = db->nDb;
for(i=0, mask=1; i<nDb; i++, mask += mask){
if( i!=1 && (mask & p->btreeMask)!=0 && ALWAYS(aDb[i].pBt!=0) ){
sqlite3BtreeEnter(aDb[i].pBt);
}
}
p->iMutexCounter = mutexCounterSum(p);
#endif
}
/*
** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
*/
void sqlite3VdbeLeave(Vdbe *p){
#ifndef SQLITE_OMIT_SHARED_CACHE
int i;
yDbMask mask;
sqlite3 *db = p->db;
Db *aDb = db->aDb;
int nDb = db->nDb;
/* Assert that the all mutexes have been held continously since
** the most recent sqlite3VdbeEnter() or sqlite3VdbeMutexResync().
*/
assert( mutexCounterSum(p) == p->iMutexCounter );
for(i=0, mask=1; i<nDb; i++, mask += mask){
if( i!=1 && (mask & p->btreeMask)!=0 && ALWAYS(aDb[i].pBt!=0) ){
sqlite3BtreeLeave(aDb[i].pBt);
}
}
#endif
}
/*
** Recompute the sum of the mutex counters on all btrees used by the
** prepared statement p.
**
** Call this routine while holding a sqlite3VdbeEnter() after doing something
** that might cause one or more of the individual mutexes held by the
** prepared statement to be released. Calling sqlite3BtreeEnter() on
** any BtShared mutex which is not used by the prepared statement is one
** way to cause one or more of the mutexes in the prepared statement
** to be temporarily released. The anti-deadlocking logic in
** sqlite3BtreeEnter() can cause mutexes to be released temporarily then
** reacquired.
**
** Calling this routine is an acknowledgement that some of the individual
** mutexes in the prepared statement might have been released and reacquired.
** So checks to verify that mutex-protected content did not change
** unexpectedly should accompany any call to this routine.
*/
void sqlite3VdbeMutexResync(Vdbe *p){
#if !defined(SQLITE_OMIT_SHARED_CACHE) && defined(SQLITE_DEBUG)
p->iMutexCounter = mutexCounterSum(p);
#endif
}
#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
/*
@@ -1959,33 +2065,6 @@ int sqlite3VdbeCloseStatement(Vdbe *p, int eOp){
return rc;
}
/*
** If SQLite is compiled to support shared-cache mode and to be threadsafe,
** this routine obtains the mutex associated with each BtShared structure
** that may be accessed by the VM passed as an argument. In doing so it
** sets the BtShared.db member of each of the BtShared structures, ensuring
** that the correct busy-handler callback is invoked if required.
**
** If SQLite is not threadsafe but does support shared-cache mode, then
** sqlite3BtreeEnterAll() is invoked to set the BtShared.db variables
** of all of BtShared structures accessible via the database handle
** associated with the VM. Of course only a subset of these structures
** will be accessed by the VM, and we could use Vdbe.btreeMask to figure
** that subset out, but there is no advantage to doing so.
**
** If SQLite is not threadsafe and does not support shared-cache mode, this
** function is a no-op.
*/
#ifndef SQLITE_OMIT_SHARED_CACHE
void sqlite3VdbeMutexArrayEnter(Vdbe *p){
#if SQLITE_THREADSAFE
sqlite3BtreeMutexArrayEnter(&p->aMutex);
#else
sqlite3BtreeEnterAll(p->db);
#endif
}
#endif
/*
** This function is called when a transaction opened by the database
** handle associated with the VM passed as an argument is about to be
@@ -2058,7 +2137,7 @@ int sqlite3VdbeHalt(Vdbe *p){
int isSpecialError; /* Set to true if a 'special' error */
/* Lock all btrees used by the statement */
sqlite3VdbeMutexArrayEnter(p);
sqlite3VdbeEnter(p);
/* Check for one of the special errors */
mrc = p->rc & 0xff;
@@ -2112,7 +2191,7 @@ int sqlite3VdbeHalt(Vdbe *p){
rc = sqlite3VdbeCheckFk(p, 1);
if( rc!=SQLITE_OK ){
if( NEVER(p->readOnly) ){
sqlite3BtreeMutexArrayLeave(&p->aMutex);
sqlite3VdbeLeave(p);
return SQLITE_ERROR;
}
rc = SQLITE_CONSTRAINT;
@@ -2124,7 +2203,7 @@ int sqlite3VdbeHalt(Vdbe *p){
rc = vdbeCommit(db, p);
}
if( rc==SQLITE_BUSY && p->readOnly ){
sqlite3BtreeMutexArrayLeave(&p->aMutex);
sqlite3VdbeLeave(p);
return SQLITE_BUSY;
}else if( rc!=SQLITE_OK ){
p->rc = rc;
@@ -2196,7 +2275,8 @@ int sqlite3VdbeHalt(Vdbe *p){
}
/* Release the locks */
sqlite3BtreeMutexArrayLeave(&p->aMutex);
sqlite3VdbeMutexResync(p);
sqlite3VdbeLeave(p);
}
/* We have successfully halted and closed the VM. Record this fact. */