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Fix handling of an xShmLock(SHARED, UNLOCK) call when the caller does not hold any lock on the specified slot, but another connection in the same process holds an EXCLUSIVE.

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FossilOrigin-Name: 3eb365027b885e1f61965efd53a3643b6ff441ae01e79038a091314516a50dd4
This commit is contained in:
dan
2020-08-28 20:01:06 +00:00
parent 8337da6678
commit 6acdee6765
3 changed files with 28 additions and 29 deletions
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40
src/os_unix.c
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@@ -4888,30 +4888,32 @@ static int unixShmLock(
sqlite3_mutex_enter(pShmNode->pShmMutex);
assert( assertLockingArrayOk(pShmNode) );
if( flags & SQLITE_SHM_UNLOCK ){
int ii;
int bUnlock = 1;
if( (p->exclMask|p->sharedMask) & mask ){
int ii;
int bUnlock = 1;
for(ii=ofst; ii<ofst+n; ii++){
if( aLock[ii]>((p->sharedMask & (1<<ii)) ? 1 : 0) ){
bUnlock = 0;
for(ii=ofst; ii<ofst+n; ii++){
if( aLock[ii]>((p->sharedMask & (1<<ii)) ? 1 : 0) ){
bUnlock = 0;
}
}
}
if( bUnlock ){
rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
if( bUnlock ){
rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
if( rc==SQLITE_OK ){
memset(&aLock[ofst], 0, sizeof(int)*n);
}
}else if( p->sharedMask & (1<<ofst) ){
assert( n==1 && aLock[ofst]>1 );
aLock[ofst]--;
}
/* Undo the local locks */
if( rc==SQLITE_OK ){
memset(&aLock[ofst], 0, sizeof(int)*n);
}
}else if( p->sharedMask & (1<<ofst) ){
assert( n==1 && aLock[ofst]>1 );
aLock[ofst]--;
p->exclMask &= ~mask;
p->sharedMask &= ~mask;
}
}
/* 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 );