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Unless upgrading an existing read transaction, have ENABLE_SETLK_TIMEOUT builds attempt to use a blocking lock when opening a write transaction on a wal mode database.

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FossilOrigin-Name: d6f819a9e6b35f3fd558bd93255a6a24ad690a0fa15a82b009ca9c641db983c6
This commit is contained in:
dan
2020-05-05 20:30:07 +00:00
parent 8714de97c0
commit 58021b237a
9 changed files with 140 additions and 63 deletions
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18
src/os_unix.c
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@@ -4819,22 +4819,24 @@ static int unixShmLock(
assert( pShmNode->hShm>=0 || pDbFd->pInode->bProcessLock==1 );
assert( pShmNode->hShm<0 || pDbFd->pInode->bProcessLock==0 );
/* Check that, if this to be a blocking lock, that locks have been
** obtained in the following order.
/* Check that, if this to be a blocking lock, no locks that occur later
** in the following list than the lock being obtained are already held:
**
** 1. Checkpointer lock (ofst==1).
** 2. Recover lock (ofst==2).
** 2. Write lock (ofst==0).
** 3. Read locks (ofst>=3 && ofst<SQLITE_SHM_NLOCK).
** 4. Write lock (ofst==0).
**
** In other words, if this is a blocking lock, none of the locks that
** occur later in the above list than the lock being obtained may be
** held. */
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
assert( pDbFd->iBusyTimeout==0
|| (flags & SQLITE_SHM_UNLOCK) || ofst==0
|| ((p->exclMask|p->sharedMask)&~((1<<ofst)-2))==0
);
assert( (flags & SQLITE_SHM_UNLOCK) || pDbFd->iBusyTimeout==0 || (
(ofst!=2) /* not RECOVER */
&& (n==1) /* Single lock only */
&& (ofst!=1 || (p->exclMask|p->sharedMask)==0)
&& (ofst!=0 || (p->exclMask|p->sharedMask)<3)
&& (ofst<3 || (p->exclMask|p->sharedMask)<(1<<ofst))
));
#endif
mask = (1<<(ofst+n)) - (1<<ofst);