Ok, I think I understand the complete picture.
At Mon, 06 Mar 2017 15:58:56 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI
<horiguchi.kyot...@lab.ntt.co.jp> wrote in
> > 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.
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
@@ -115,7 +115,9 @@ static char **LWLockTrancheArray = NULL;
static int LWLockTranchesAllocated = 0;
#define T_NAME(lock) \
+ ((lock)->tranche < LWTRANCHE_FIRST_USER_DEFINED ? \
+ LWLockTrancheArray[(lock)->tranche] : \
+ NamedLWLockTrancheArray[(lock)->tranche - LWTRANCHE_FIRST_USER_DEFINED].trancheName)
* This points to the main array of LWLocks in shared memory. Backends inherit
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