1 files changed, 5 insertions, 1 deletions
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h
index df3df298ae9..c684964a34f 100644
--- a/src/include/storage/lwlock.h
+++ b/src/include/storage/lwlock.h
@@ -94,7 +94,10 @@ typedef enum LWLockId
 typedef enum LWLockMode
 {
 	LW_EXCLUSIVE,
-	LW_SHARED
+	LW_SHARED,
+	LW_WAIT_UNTIL_FREE	/* A special mode used in PGPROC->lwlockMode, when
+						 * waiting for lock to become free. Not to be used
+						 * as LWLockAcquire argument */
 } LWLockMode;
 
 
@@ -105,6 +108,7 @@ extern bool Trace_lwlocks;
 extern LWLockId LWLockAssign(void);
 extern void LWLockAcquire(LWLockId lockid, LWLockMode mode);
 extern bool LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode);
+extern bool LWLockWaitUntilFree(LWLockId lockid, LWLockMode mode);
 extern void LWLockRelease(LWLockId lockid);
 extern void LWLockReleaseAll(void);
 extern bool LWLockHeldByMe(LWLockId lockid);