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In SQLITE_ENABLE_SETLK_TIMEOUT builds, use blocking locks in place of sleep() when opening a read-transaction.

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FossilOrigin-Name: a51ef39998e25e86bd0600e71d15011b12e05f4319608018293bdaecb09e8c97
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dan
2023-11-27 19:22:50 +00:00
parent 48cca2422e
commit e52854a9e6
4 changed files with 59 additions and 26 deletions
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13
src/os_unix.c
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@@ -4595,7 +4595,20 @@ static int unixLockSharedMemory(unixFile *pDbFd, unixShmNode *pShmNode){
pShmNode->isUnlocked = 1;
rc = SQLITE_READONLY_CANTINIT;
}else{
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
/* Do not use a blocking lock here. If the lock cannot be obtained
** immediately, it means some other connection is truncating the
** *-shm file. And after it has done so, it will not release its
** lock, but only downgrade it to a shared lock. So no point in
** blocking here. The call below to obtain the shared DMS lock may
** use a blocking lock. */
int iSaveTimeout = pDbFd->iBusyTimeout;
pDbFd->iBusyTimeout = 0;
#endif
rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1);
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
pDbFd->iBusyTimeout = iSaveTimeout;
#endif
/* The first connection to attach must truncate the -shm file. We
** truncate to 3 bytes (an arbitrary small number, less than the
** -shm header size) rather than 0 as a system debugging aid, to