Re: [HACKERS] [BUG FIX] Removing NamedLWLockTrancheArray

Ok, I think I understand the complete picture.

At Mon, 06 Mar 2017 15:58:56 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in
<20170306.155856.198084190.horiguchi.kyotaro@lab.ntt.co.jp>
> > I can guess two ways to fix this. One is change the definition of
> > T_NAME.
> > 
> > | #define T_NAME(l) \
> > |   ((l)->tranche < LWTRANCHE_FIRST_USER_DEFINED ? \
> > |    LWLockTrancheArray[(l)->tranche] : \
> > |    NamedLWLockTrancheArray[(l)->tranche - LWTRANCHE_FIRST_USER_DEFINED]
> > 
> > It makes the patch small but I don't thing the shape is
> > desirable.
> > 
> > Then, the other way is registering named tranches into the main
> > tranche array. The number and names of the requested named
> > tranches are known to postmaster so they can be allocated and
> > initialized at the time.
> > 
> > The mapping of the shared memory is inherited to backends so
> > pointing to the addresses in shared memory will work in the
> > !EXEC_BACKEND case. I confirmed that the behavior is ensured also
> > in EXEC_BACKEND case.

But this doesn't work for
LWLockNewTrancheId/LWLockRegisterTranche and it is valuable
interface. So the measure we can take is redefining T_NAME.

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index ab81d94..7c4c8f4 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -115,7 +115,9 @@ static char **LWLockTrancheArray = NULL;static int    LWLockTranchesAllocated = 0;#define
T_NAME(lock)\
 
-    (LWLockTrancheArray[(lock)->tranche])
+    ((lock)->tranche < LWTRANCHE_FIRST_USER_DEFINED ? \
+    LWLockTrancheArray[(lock)->tranche] : \
+     NamedLWLockTrancheArray[(lock)->tranche - LWTRANCHE_FIRST_USER_DEFINED].trancheName)/* * This points to the main
arrayof LWLocks in shared memory.  Backends inherit