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-rw-r--r--src/os_unix.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/src/os_unix.c b/src/os_unix.c
index dab03c97f..7362a1320 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -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