/*
** Enter the mutex of every btree in the array. This routine is
** called at the beginning of sqlite3VdbeExec(). The mutexes are
** exited at the end of the same function.
*/
void sqlite3BtreeMutexArrayEnter(BtreeMutexArray *pArray)
{
int i;
for (i = 0; i < pArray->nMutex; i++)
{
Btree *p = pArray->aBtree[i];
/* Some basic sanity checking */
assert(i == 0 || pArray->aBtree[i - 1]->pBt < p->pBt);
assert(!p->locked || p->wantToLock > 0);
/* We should already hold a lock on the database connection */
assert(sqlite3_mutex_held(p->db->mutex));
/* The Btree is sharable because only sharable Btrees are entered
** into the array in the first place. */
assert(p->sharable);
p->wantToLock++;
if (!p->locked)
{
lockBtreeMutex(p);
}
}
}
/*
** Leave the mutex of every btree in the group.
*/
void sqlite3BtreeMutexArrayLeave(BtreeMutexArray *pArray)
{
int i;
for (i = 0; i < pArray->nMutex; i++)
{
Btree *p = pArray->aBtree[i];
/* Some basic sanity checking */
assert(i == 0 || pArray->aBtree[i - 1]->pBt < p->pBt);
assert(p->locked);
assert(p->wantToLock > 0);
/* We should already hold a lock on the database connection */
assert(sqlite3_mutex_held(p->db->mutex));
p->wantToLock--;
if (p->wantToLock == 0)
{
unlockBtreeMutex(p);
}
}
}
/*
** Add a new Btree pointer to a BtreeMutexArray.
** if the pointer can possibly be shared with
** another database connection.
**
** The pointers are kept in sorted order by pBtree->pBt. That
** way when we go to enter all the mutexes, we can enter them
** in order without every having to backup and retry and without
** worrying about deadlock.
**
** The number of shared btrees will always be small (usually 0 or 1)
** so an insertion sort is an adequate algorithm here.
*/
void sqlite3BtreeMutexArrayInsert(BtreeMutexArray *pArray, Btree *pBtree)
{
int i, j;
BtShared *pBt;
if (pBtree == 0 || pBtree->sharable == 0)
{
return;
}
#if !NDEBUG
{
for (i = 0; i < pArray->nMutex; i++)
{
assert(pArray->aBtree[i] != pBtree);
}
}
#endif
assert(pArray->nMutex >= 0);
assert(pArray->nMutex < ArraySize(pArray->aBtree) - 1);
pBt = pBtree->pBt;
for (i = 0; i < pArray->nMutex; i++)
{
assert(pArray->aBtree[i] != pBtree);
if (pArray->aBtree[i]->pBt > pBt)
{
for (j = pArray->nMutex; j > i; j--)
{
pArray->aBtree[j] = pArray->aBtree[j - 1];
}
pArray->aBtree[i] = pBtree;
pArray->nMutex++;
return;
}
}
pArray->aBtree[pArray->nMutex++] = pBtree;
}